Bn W " ^^ '^^
^iiy
'■/r^f
:*■
# rf
£ni^]W\L iU. Llb.^
The August 1, 1975
Oroville Earthquake
Investigations
P w
^. ^mm m *mt ^--r *>*-•*
njs* ■■ ■.;,■ «JiaRH"''.-<£i»«Ji«'.
ON THE COVER:
Aerial View of Oroville Facilities
Department of
Water Resources
Bulletin 203-78
The August 1, 1975
Oroville Earthquake
Investigations
February 1979
Huey D. Johnson
Secretary for Resources
The Resources
Agency
Edmund G. Brown Jr.
Governor
State of
California
Ronald B. Robie
Director
Department of
Water Resources
Digitized by the Internet Archive
in 2010 with funding from
University of California Libraries
http://www.archive.org/details/august11975orovi20378cali
FOREWORD
The epicenter of the 1975 earthquake near Oroville, California
was close to the Oroville-Thermalito features of the California State Water
Project. Therefore, the Department of Water Resources initiated structural
reanalyses of the Project facilities and seismological and geological
investigations .
The performance of the Oroville-Thermalito facilities during the
August 1975 earthquake sequence, reported in Bulletin 203 (April 1977),
demonstrated their ability to withstand that seismic loading. No structural
damage occurred. The only damage was to a few of the secondary facilities;
this damage was only superficial.
The Department conducted intensive investigations to determine :
1. Geologic and tectonic conditions
2. Fault mechanism and orientation
3. Crustal movements
4. Public safety as it relates to the Department's facilities.
The Department established a Special Consulting Board for the
Oroville Earthquake, consisting of nine experts in the fields of seismology,
geology and dam design to review the Department's investigations and make
recommendations .
Bulletin 203-78 presents a detailed reanalysis of the Department's
facilities and results of the detailed seismological and geological investi-
gations. On the basis of determinations from the investigations completed
to date, the Department concludes that the Oroville facilities do not pose
a threat to public safety.
The reanalyses of Thermalito Forebay, Afterbay and Power Plant
Headworks, and the Bidwell Canyon Saddle Dam are still in progress, with
publication planned by mid 1979.
Ronald B. Robie, Director
Department of Water Resources
The Resources Agency
State of California
state of California
Edmund G. Brown Jr. , Governor
The Resources Agency
Huey D. Johnson, Secretary for Resources
DEPARTMENT OF WATER RESOURCES
Ronald B. Robie, Director
Charles R. Shoemaker Gerald H. Meral Robert W. James
Acting Deputy Director Deputy Director Deputy Director
Jack B. Johnston
Acting Assistant Director
Division of Operations and Maintenance
Howard H. Eastin Division Chief
Lawrence A, Mullnix Chief, Water Engineering Office
Clifford V. Lucas Chief, Civil Maintenance Branch
Philip F. Johns Chief, Oroville Field Division
Authors
Chapter I
John R. Campbell Project Surveillance Section
Chapter III
Paul W, Morrison, Jr Earthquake Engineering
Chapter IV
John R. Campbell Project Surveillance Section
Chapter IX
J. P. Cedarholm Civil Maintenance Section
Division of Design and Construction
Gordon W, Dukleth Division Chief
Keith G. Barrett Chief, Design Office
Ernest C. James Chief, Civil Design Branch
Division of Design and Construction (Continued)
John W. Marlette Chief, Project Geology Branch
William M. Verigin Chief, Dams and Canals Section
Donald C. Steinwert Chief, Structures Section
Authors
Chapter II
John W. Marlette Chief, Project Geology Branch
Robert J. Akers Project Geology Branch
Kenneth A. Cole Project Geology Branch
Richard D. McJunkin Project Geology Branch
Chapter V
William D. Hammond Dams and Canals Section
Leslie F. Harder Dams and Canals Section
Chapter VI
Samuel J. Linn, Jr Structural Section
Edgar R. Najera Structural Section
Chapter VII
Samuel J. Linn, Jr. Structural Section
Edgar R. Najera Structural Section
Chapter VIII
Arnold E, Eskel Structural Section
Samuel J. Linn, Jr Structural Section
Edited by
Earl G. Bingham, Reports Administration
CONTENTS
Page
Foreword ■'■■'■-'■
IV
Organization
CHAPTER I. INTRODUCTION
Purpose 1
Description of the Oroville Facilities 1
The Investigating Organization 3
Reanlysis of Project Structures for Earthquake Safety 4
Summary of Conclusions and Recommendations 5
Geological Investigations (Chapter II) 5
Seismology (Chapter III) 6
Vertical and Horizontal Geodesy (Chapter IV) 6
Oroville Dam, Evaluation of Seismic Stability (Chapter V) 7
Oroville Dam, Flood Control Outlet Structure (Chapter VI) 7
Thermalito Diversion Dam (Chapter VII) 7
Reappraisal of Secondary Structures (Chapter VIII) 7
Fish Barrier Dam 7
Edward Hyatt Powerplant 7
Thermalito Powerplant 7
Miscellaneous Structures 8
Bridges 8
Switchyards 8
Contingency Plan for Seismic Emergencies (Chapter IX) 8
Department's Findings 8
Uncompleted Reports 8
-*:*>■ Safety Review Requirements 8
Report of the Special Consulting Board for the Oroville Earthquake 9
Review by the Division of Mines and Geology 13
CHAPTER II. GEOLOGIC INVESTIGATIONS
Purpose of Investigation 15
Previous Work 15
Scope of Investigation 17
Seismic History 19
The 1975 Earthquake Series 21
Ground Cracking 23
Ground Elevation Changes 26
Area Lineaments 27
Geologic Setting 30
Geographic Location 30
Geologic Framework 30
Descriptive Geology 33
Bedrock Series Rocks 33
Melange 34
Previous Investigations and Age 34
Contact Relationships 34
Lithologic Description 35
Arc Rocks 38
Previous Investigations and Age 38
Contact Relationships 38
Lithologic Description 38
Monte de Oro Formation 40
Previous Investigations and Age 40
Contact Relationships 40
Lithologic Description 41
Smartville Ophiolite 41
Previous Investigations and Age 41
Contact Relationships 42
Litholigic Description 42
Intrusive Rocks 47
Previous Investigations and Age ; 47
Contact Relationships 47
Lithologic Description 48
Origin of Sierra Nevada Plutons 49
Superjacent Series Rocks 50
Chico Formation 50
Previous Investigations and Age 50
Contact Relationships 50
Lithologic Description 50
lone Formation 51
Previous Investigations and Age 51
Contact Relationships 51
Lithologic Description - lone Formation Undifferentiated . . 51
Lithologic Description - Auriferous Gravel ... 51
Lithologic Description - Oroville Tuff 52
Love joy Formation 53
Previous Investigations and Age 53
Contact Relationships 53
Lithologic Description 54
Tuscan Formation 54
Previous Investigations and Age 54
Contact Relationships 55
Lithologic Description 55
Late Cenozoic Gravels 56
Previous Investigations 56
Contact Relationships 56
Lithologic Description 57
Quaternary Landslides 57
Structural Geology 61
Faults 61
Mesozoic Faults - Northern Foothills 65
Mesozoic Faults - Project Area 67
Swain Ravine, Paynes Peak and Prairie Creek
Lineament/Fault Zones 67
Oregon Gulch Fault 68
Monte de Oro Fault 69
Unnamed Faults . 69
Glover Ridge Fault 69
Cenozoic Fault Movement 70
Swain Ravine Lineament Fault Zone 71
vii
Prairie Creek Lineament Fault Zone 74
Paynes Peak Lineament Fault Zone 7^
Thermalito Powerplant Foundation Faults 75
Chico Lineament 75
Soda Springs Lineament 77
Web Hollow Lineament 77
Paradise-Magalia Lineament 77
Summary 79
Mesozoic Folds 79
Cenozoic Folding 79
Summary of Geologic History 80
Causes of the Oroville Earthquake 82
^^^servoir- Induced Seismicity 83
Potential Hazards to State Water Facilities 86
Groirnd Shaking 86
Fault Displacement 86
Regional Changes in Ground Elevation 87
Potential Hazard to Specific Facilities 87
Oroville Dam and Saddle Dams 87
Thermalito Forebay and Afterbay 87
Thermalito Powerplant 88
Other Structures 88
Summary and Conclusions 88
References Cited ..... 90
Addenda: Department of Water Resources Exploration Trench Logs 103
CHAPTER III. SEISMOLOGY
Introduction 123
Data 123
Results 124
Discussion 124
Conclusions 124
References Cited 139
CHAPTER IV. VERTICAL AND HORIZONTAL GEODESY
Vertical Crustal Movements 141
Introduction 141
Precise Survey Programs 141
September 1967 141
July-September 1968 142
October-November 1969 142
August-September 1975 142
January-April 1976 142
September-November 1976 142
September-November 1977 142
Precise Survey Adjustment 143
Free Adjustment 143
Spur Lines 144
Elevation Differential Isograms 146
General 146
September 1967-October 1969 146
October 1969-August 1975 146
September 1967-October 1977 146
August 1975-October 1976 146
October 1976-October 1977 153
August 1975-October 1977 153
Elevation Differential Along Lines 153
General 153
Avocado 153
Bald Rock 153
Bidwell 153
Bidwell Canyon Saddle Dam 157
Canyon Drive 157
Cleveland Hill 157
Dam 157
Dunstone 157
Feather Falls 157
Foothill 157
Miners Ranch 157
Mission Olive 157
Morris 167
Olive 167
Oro-Bangor 167
Oroville 167
Potter 167
Richvale 167
Thompson Flat 167
Wyn-Miners Ranch 167
103 167
Oroville Dam Crest Differential Settlement 167
General 167
Commentary 181
Conclusions 181
Horizontal Earth Movements 181
Introduction 181
Horizontal Geodetic Control and Triangulation Programs 181
September 1967 181
April 1968 183
August- Sept ember 1975 183
Computations and Analyses 183
Commentary 185
Conclusions 185
CHAPTER V. OROVILLE DAM: EVALUATION OF SEISMIC STABILITY
Acknowledgments 187
1. Introduction 188
Background 189
Commentary 190
Summary of Findings 190
Conclusions 191
2. Description of Embankment Materials and Dynamic Instrumentation. . . 192
Embankment Materials 192
Dynamic Instrumentation 194
Original System 194
Upgraded System 195
3. Recorded Embankment Response to the 1975 Earthquakes 197
General 197
Recorded Events 197
August 1, 1975 197
August 5, 1975 199
September 27, 1975 199
Observed Natural Period 201
4. Analysis of Static Stresses by Finite Element Method 203
General 203
Material Properties 204
Static Stress Analysis 205
Seepage Forces 205
5. Determination of Dynamic Shear Modulus and Damping Values for
Embankment Shell Material 208
General 208
Cyclic Triaxial Test 209
Analysis of Recorded Embankment Response During the 1975
Earthquakes 211
General 211
Natural Period for Two-Dimensional Analysis 213
Shear Strain for Two-Dimensional Analysis 213
Shear Modulus Reduction Factor 213
K„ vs. Natural Period 214
RiSP of K 214
Comparison of Observed and Computed Crest Motions 214
Embankment Response Model 216
August 1 Event 216
September 27 Event 217
Dynamic Properties Adopted for Gravel Shell 217
6. Reanalysis Earthquake 221
7. Analysis of Dynamic Stresses for the Reanalysis Earthquake 229
Methods of Response Computation 229
Acceleration Response of Dam to Design Earthquake 229
Input Variables and Computed Shear Stresses 231
Influence of Shear Modulus of Shell Material 232
Influence of Shear Modulus of Core Material 233
Computer Programs LUSH and QUAD4 234
Influence of Poisson's Ratio 237
Influence of Embankment Section 239
Combined Influence of Variables 241
Three-Dimensional Effect 241
Cyclic Shear Strength 244
Cyclic Strength Test Program 244
Sample Gradations and Density 244
Modeling Embankment Shell Gradation 244
Relationship of Test Sample Density to Field Density . . . 244
Summary of Test Procedures 249
30 cm Diameter Samples 249
7.1 cm Diameter Samples 249
Results of Cyclic Triaxial Tests 250
Investigation of Sample Behavior of Dense Sands in Static and
Cyclic Triaxial Tests 251
Objective 251
Program and Procedures 254
Static Tests on Monterey 0 Sand 256
Cyclic Tests on Monterey 0 Sand 260
Cyclic Tests on Oroville Sand 262
Analysis of Test Results 268
Extension Strain 268
Necking Behavior 268
Sample "Tension" 268
Cyclic Strength Interpretations Considered 276
Strength Interpretation I 276
Strength Interpretation II 276
Evaluation of Performance 281
General Considerations 281
Method of Evaluation 281
Failure Planes 281
Equivalent Regular Stress Time History 282
Cases Analyzed and Assumptions 282
Case a 284
Case b 284
Case c 284
Case d 285
Comparison of Cases 285
Predicted Behavior - Best Judgment Case 285
Shell K g^ 285
Cyclic sStar Strength 285
Three-Dimensional Effect 285
Drainage 285
Predicted Behavior 286
Estimated Displacements for Conservative Assumptions 287
References , 288
CHAPTER VI. SEISMIC ANALYSIS OF THE OROVILLE DAM FLOOD
CONTROL OUTLET STRUCTURE
Commentary 291
Conclusion 294
Earthquake Analysis of the Oroville Dam Flood Control Outlet
Structure, June 1977, by Edward L. Wilson, Frederick E. Peterson,
and Ashraf Habibullah 299
CHAPTER VII. SEISMIC ANALYSIS OF THE
THERMALITO DIVERSION DAM
Commentary 351
Earthquake Response Analysis of Thermalito Diversion Dam By
Anil K. Chopra 355
CHAPTER VIII. REAPPRAISAL OF
SECONDARY STRUCTURES
Introduction 389
Fish Barrier Dam 389
Description 389
Original Seismic Analysis 389
Recommendation for Seismic Reanalysis 395
Power and Pumping Plant Facilities 395
Edward Hyatt Powerplant 399
Conclusion 399
Thermalito Powerplant 399
Conclusion 395
Miscellaneous Structures 402
Oroville Operations and Maintenance Center 402
Oroville Dam 402
Thermalito Forebay and Afterbay 402
Feather River Fish Hatchery 402
Conclusion 403
Bridges 403
Conclusion 403
Swtichyard Structures and Apparatus 403
Conclusion 404
CHAPTER IX. CONTINGENCY PLAN FOR SEISMIC EMERGENCIES
Organization and Responsibilities 405
Division Policy 405
Division Plan of Operation 405
Oroville Field Division Command Post 405
Operational Command Post 406
Operational Facilities 406
Operational Plan 406
Security Command Post 406
Security Plan 406
Procedures for Reacting to Seismic Events 406
Detection 406
Earthquake Magnitudes and Epicenters 406
Criteria for Notification 407
Response 407
Inspection of Project Facilities Following an Earthquake ...... 408
Rapid Response Inspection Plan 408
Follow-up Inspection Plan 408
Returning Facilities and Equipment to Full Operational Status 408
xii
Regulating Features 409
Nonregulating Features 409
List of Operating Criteria for Regulating Lake Oroville 414
Decision Making Criteria for Operating Features Which Can Be
Regulated 414
Palermo Outlet 414
Oroville Dam Spillway 414
River Outlet Valves 414
Edward Hyatt Intake 415
Edward Hyatt Powerplant 415
Critical Conditions for Features Which Cannot be Regulated 416
Oroville Dam 416
Bidwell Canyon Saddle Dam 416
Parish Camp Saddle Dam 417
Oroville Dam Spillway 417
Edward Hyatt Intake and Penstock 417
Palermo Intake and Outlet 417
River Outlet Valve Chamber 417
List of Operating Criteria for Regulating Thermalito Diversion Pool . . . 417
Decision Making Criteria for Operating Regulating Features 417
Thermalito Diversion Dam 417
Critical Conditions for Features Which Cannot Be Regulated 418
Thermalito Diversion Dam 418
Thermalito Power Canal Headworks 418
List of Operating Criteria for Regulating Thermalito Forebay Reservoir
and Power Canal 418
Decision-Making Criteria for Operating Regulating Features 418
Thermalito Intake Structure 418
Thermalito Powerplant 418
Critical Conditions for Features Which Cannot Be Regulated 419
Thermalito Forebay Dam 419
Thermalito Intake Structure 419
Thermalito Power Canal (Cut Section) 420
Thermalito Power Canal (Fill Section) 420
List of Operating Criteria for Regulating Thermalito Afterbay Reservoir . 420
Decision-Making Criteria for Operating Regulating Features 420
Thermalito Afterbay River Outlet 420
Sutter-Butte Outlet 420
PG&E Outlet 420
Western Canal and Richvale Outlets 420
Thermalito Afterbay Dam Ground Water Pumping System 420
Critical Condition for Features Which Cannot Be Regulated 421
Thermalito Afterbay Dam 421
Thermalito Power House Structure 421
Thermalito Afterbay River Outlet 421
Sutter-Butte Outlets 421
PG&E Outlet 421
Western-Richvale Outlets 421
Commentary 421
Conclusion 421
TABLES
No. Page
1 Exploration Trenches in Foothill Belt — Oroville to Auburn Area ... 62
2 Summary of Geologic Events 80
3 Earthquake Epicenters, June 1975-December 1975 133
4 Earthquake Epicenters, January 1976-May 1978 137
5 Value of Stress-Strain Parameters for Analysis of Oroville Dam . . . 204
6. Static Stress Comparison 205
FIGITRES
CHAPTER I
1 Oroville Dam 1
2 Location Map, Oroville Facilities 2
3 Thermalito Diversion Dam 3
4 Thermalito Forebay Dam 4
5 Thermalito Afterbay Dam 4
CHAPTER II
6 Location map of six quadrangle study area 16
7 Historic earthquakes within a 100 km (62 mi) radius of Oroville . . 18
8 Aftershock locations of the Oroville earthquake 20
9 Locations of the Cleveland Hill and Mission Olive crack zones and
sites of Department of Water Resources exploration trenches ... 22
10 Ground cracking that resulted from the August 1, 1975, Oroville
earthquake 23
11 Close-up view of a ground crack on southwest slope of Cleveland
Hill 23
12 Locations of ground cracking from the Oroville earthquake and major
lineaments in the southern study area 24
13 Aerial view of northern limit of ground cracking 25
Figure No. Page
14 Changes in ground elevations around Lake Oroville, August 1975 to
October 1976 28
15 Changes in crest elevations of Bidwell Canyon Saddle Dam between
November 1967 and October 1977 29
16 Lineaments and faults in the northwestern Sierran foothills .... 31
17 Natural geologic provinces of California with field area location . 32
18 Small-scale parasitic isoclinal fold within melange metasedimentary
rock 35
19 Relict bedding cross cut by foliation in melange metasedimentary
rock 35
20 Sheared volcaniclastic metaconglomerate in melange metasedimentary
rock 36
21 Exotic marble block in melange 36
22 Sample of olistostromal marble-phyllite collected in melange .... 37
23 Relict bedding in arc metasedimentary rock 39
24 Arc complex metavolcanic tuff breccia 39
25 Arc complex relict pillow and flow lavas cut by fault 39
26 Relict bedding and cross-bedding in arc tuff breccia and tuffaceous
metasedimentary rock 40
27 Igneous stratigraphy of Standard Oceanic Crust and Smartville
ophiolite 43
28 Well developed metavolcanic Smartville pillows 43
29 Well developed metavolcanic Smartville pillows 44
30 Sheared metavolcanic Smartville pillows 44
31 Metavolcanic Smartville sheeted dikes 45
32 Gabbroic screen rock in Smartville metavolcanic sheeted dikes ... 45
33 Granophyric screen rock in Smartville metavolcanic sheeted dikes . . 46
34 Mesozoic time scale with corresponding intrusive epochs in the
Sierra Nevada region 47
35 Metavolcanic xenoliths within Swedes Flat plutonic rock 48
36 View of Bald Rock exhibiting surface exposure and exfoliation
that is typical of the Sierra Nevada complex 49
Figure No. Page
37 lone Formation auriferous gravel with intercalated Oroville tuff
(Mehrten Formation-?) 52
38 Lovejoy Formation basalt disconformably overlying lone Formation . . 53
39 Lovejoy Formation basalt on North Table Mountain 54
40 Young erosional surface cut into Tuscan Formation that is adjacent
to older and structurally higher erosional surface cut into
mesozoic metamorphic rock
41 Tuscan Formation volcanic conglomerate, cross-bedded sand and laharic
mudflow breccia 56
42 Late Cenozoic gravel and cross-bedded sand (Red Bluff Formation-?) . 57
43 Late Cenozoic gravel (Red Bluff Formation-?) unconformably overlying
Oroville tuff (Mehrten Formation-?) along the Feather River .... 58
44 Landslide in lone Formation 59
45 Stringtown Mountain landslides 59
46 Prehistoric landslide north slope of Bloomer Hill 60
47 Major lineaments in the northwestern Sierran foothills showing
exploration localities with faulting assessments for each site . . 61
48 Foothills Fault System of the western Sierra Nevada, California . . 66
49 Aerial view of Glover Ridge (klippe) and traced location of
Glover Ridge Fault 70
50 Aerial northeast view of the Cleveland Hill Fault along the
western side of Cleveland Hill 71
51 Aerial view of Chico monocline 75
52 Normal fault in Tuscan Formation 76
53 Normal fault in Tuscan Formation 76
54 Vertical aerial view of eastern fracture zone developed in Tuscan
Formation 77
55 Map with cross section oriented perpendicular to suspected fault
through Magalia Reservoir 78
56 Comparison of foreshock-af tershock patterns for the Oroville
earthquake and Mogi's "Type II" (reservoir-induced earthquakes). . 84
57 Water level history of Lake Oroville from initial filling to
September 1978 84
CHAPTER III
Figure No. Page
58 DWR-USGS Oroville Sensitive Seismographic Network 125
59 Oroville Foreshocks, Mainshock, and Aftershocks; June 1, 1975-
December 31, 1975 126
60 1975 Oroville Earthquake Hypocenters (North Vertical Cross
Section) 127
61 1975 Oroville Earthquake Hypocenters (Middle Vertical Cross
Section) 127
62 1975 Oroville Earthquake Hypocenters (South Vertical Cross
Section) 128
63 Oroville Earthquake Epicenters (January 1, 1976-May 31, 1978) . . . 129
64 Oroville Earthquake Hypocenters, 1976-May 31, 1978 (North Vertical
Cross Section) 130
65 Oroville Earthquake Hypocenters, 1976-May 31, 1978 (Middle Vertical
Cross Section) 130
66 Oroville Earthquake Hypocenters, 1976-May 31, 1978 (South Vertical
Cross Section) 131
67 Oroville Earthquake Hypocenters, August 2, 1975-December 31, 1975
(Middle Vertical Cross Section) 131
68 Oroville Sequence, Number of Aftershocks/Month, Water Surface
Elevation (August 1975-June 1978) 132
CHAPTER IV
Lake Oroville Water Surface Elevation 142
70 Oroville Area Level Lines (1977) 143
71 Precise Level Net for Study of Lake Oroville - 1967 144
72 Precise Level Net for Study of the Oroville Earthquake - 1977 . . . 145
73 Elevation Differential Isogram — September 1967-October 1969 .... 147
74 Elevation Differential Isogram — October 1969-August 1975 148
75 Elevation Differential Isogram — September 1967-October 1977 .... 149
76 Elevation Differential Isogram — August 1975-October 1976 150
77 Elevation Differential Isogram — October 1976-October 1977 151
Figure No. Page
78 Elevation Differential Isogram — August 1975- October 1977 152
79 Avocado Elevation Differentials 154
80 Bald Rock Elevation Differentials 155
81 Bidwell Elevation Differentials 156
82 Bidwell Canyon Saddle Dam Elevation Differentials 158
83 Canyon Drive Elevation Differentials 159
84 Cleveland Hill Elevation Differentials 160
85 Dam Elevation Differentials 161
86 Dunstone Elevation Differentials 162
87 Feather Falls Elevation Differentials 163
88 Foothill Elevation Differentials 164
89 Miners Ranch Elevation Differentials 165
90 Mission Olive Elevation Differentials 166
91 Morris Elevation Differentials 168
92 Olive Elevation Differentials 169
93 Oro-Bangor Elevation Differentials 170
94 Oroville Elevation Differentials 171
95 Potter Elevation Differentials 172
96 Richvale Elevation Differentials (1 of 2) 173
97 Richvale Elevation Differentials (2 of 2) 174
98 Thompson Flat Elevation Differentials 175
99 Wyn-Miners Ranch Elevation Differentials 176
100 103 Elevation Differentials (1 of 3) 177
101 103 Elevation Differentials (2 of 3) 178
102 103 Elevation Differentials (3 of 3) 179
103 Oroville Dam Crest Differential Settlement (References to the
Abutments) 180
104 Horizontal Geodetic Control and Triangulation Net (1967-1975) . . . 182
xviii
CHAPTER V
Figure No. Page
105 Location Map 188
106 Oroville Maximum Section 192
107 Average Gradation Curves of Oroville Dam Materials 193
108 Oroville Dam Embankment, Original Dynamic Instrumentation 194
109 Oroville Dam Embankment, Present Dynamic Instrumentation (December,
1978) 196
110 Acceleration Records, Main Event of August 1, 1975 198
111 Acceleration Records with Corrected Time Scales, August 1, 1975 . . 200
112 Acceleration Records, Event of August 5, 1975 201
113 Acceleration Records, Event of September 27, 1975 202
114 Acceleration Response Spectra for Crest Motions, Event of
August 1, 1975 203
115 Finite Element Mesh, Maximum Section Oroville Dam . . .' 204
116 Contours of Effective Maximum Principal Stress in Oroville
Dam, Full Reservoir 206
117 Contours of Effective Minimum Principal Stress in Oroville
Dam, Full Reservoir 206
118 Contours of Maximum Shear Stress in Oroville Dam, Full Reservoir . . 207
119 Orientation of Principal Stresses 207
120 In-Situ Shear Moduli for Saturated Clays 208
121 Sample Gradation for Cyclic Triaxial Tests 209
122 Modulus Determinations for Gravelly Soils 210
123 Comparison of Damping Ratios for Gravelly Soils and Sands 211
124 Section on Long Chord of Dam Axis 212
125 Comparison of Natural Periods for Two-Dimensional and Three-
Dimensional Embankment in Triangular Canyon 212
126 Shear Modulus Reduction Curve for Embankment Soils 213
127 Static Shear Strength Envelopes for Core Material 214
Figure No. Page
128 K2iiiax ^^ • Natural Period 214
129 Maximum Accelerations Computed from 3D and Plane Strain Analyses
Using Base Motions from Taft Record (after Makdisi) 215
130 Damping Ratios for Embankment Soils 217
131 Comparison of Acceleration Time Histories, August 1 Main Shock . . . 218
132 Comparison of Displacement Time Histories and Acceleration Response
Spectra for Crest Motions, August 1 Main Shock 219
133 Comparison of Acceleration Time Histories and Response Spectra,
September 27 Aftershocks 220
134 Lineaments, Faults and Recorded Epicenters Around Oroville 222
135 Location of Faults in Relation to Oroville Dam 223
136 Relationship of Oroville Dam to Assumed Northward Extension of
Fault 224
137 Earthquake Ground Motion Characteristics 226
138 Reanalysis Earthquake 227
139 Response Spectra for the Reanalysis Earthquake 228
140 Acceleration Response to Reanalysis Earthquake 230
141 Influence of Shear Modulus of Shell Material on Computed Maximum
Horizontal Dynamic Shear Stresses 232
142 Influence of Shear Modulus of Core on Computed Maximum Horizontal
Dynamic Shear Stresses 234
143 Comparison of Horizontal Dynamic Shear Stress Time Histories from
LUSH and QUAD4 235
144 Comparison of Horizontal Dynamic Shear Stress Time Histories from
LUSH and QUAD4 236
145 Comparison of Computed Maximum Horizontal Dynamic Shear Stresses
by Computer Programs LUSH and QUAD4 237
146 Model Embankment for Determining Influence of Poisson's Ratio on
Dynamic Shear Stresses 238
147 Influence of Poisson's Ratio on Computed Dynamic Shear Stresses . . 239
148 Comparison of Computed Maximum Horizontal Dynamic Shear Stresses
for Different Embankment Sections 240
Figure No. Page
149 Comparison of Maximum Horizontal Shear Stresses Determined from
3D and Plane Strain Analyses Using Base Motions from Taft
Record (after Makdisi) 242
150 Estimated Three-Dimensional Effect on Computed Maximum Horizontal
Dynamic Shear Stresses 243
151 Field and Modeled Oroville Gravel Gradations 245
152 Final Statistical Analysis - Zone 3, Percent Compaction 246
153 Field Control Tests - Zone 3 247
154 Maximum Density Tests - Zone 3 248
155 Cyclic Triaxial Test Records for Modeled Oroville Gravel 252
156 Cyclic Triaxial Test Records for Modeled Oroville Gravel 253
157 Cyclic Triaxial Test Records for Modeled Oroville Gravel 254
158 Monterey "0" Sand and Oroville Sand Gradations 255
159 Typical Static Triaxial Compression Test Results for Monterey
"0" Sand 257
160 Typical Static Triaxial Extension Test Results for Monterey "0"
Sand 258
161 Summary of Static Triaxial Test Results for Dense
Monterey "0" Sand 259
162 Cyclic Triaxial Strain Envelopes for Monterey "0" Sand 260
163 Static and Cyclic Triaxial Test Results for Dense Monterey "0" Sand . 261
164 Cyclic Triaxial Test Results for Monterey "0" Sand 262
165 Cyclic Triaxial Test Records for Monterey "O" Sand 263
166 Shear Plane Development during Final Stage of Necking for Monterey
"0" Sand 264
167 Cyclic Triaxial Test Records for Monterey "0" Sand 265
168 Cyclic Triaxial Test Records for Oroville Sand 266
169 Cyclic Triaxial Test Records for Oroville Sand 267
170 Cyclic Triaxial Test Records for Modeled Oroville Gravel 269
171 Cyclic Traixial Test Records for Modeled Oroville Gravel 269
172 Cyclic Triaxial Test Records for Modeled Oroville Gravel 270
Figure No. ° ■
173 Extension/Compression Cycle for Monterey "0" Sand Cyclic
Triaxial Test 271
174 Compression/Extension Cycle for Monterey "O" Sand Cyclic Triaxial
Test 273
175 Comparison of Shaking Table and Cyclic Triaxial Test Results
for 5 Cycles 274
176 Comparison of Shaking Table and Cyclic Triaxial Test Results
for 10 Cycles 275
177 Cyclic Strength Envelopes for Strength Interpretation I - Static
and Cyclic Test Results 278
178 Typical Extrapolations of Isotropically-Consolidated Cyclic
Triaxial Tests on Modeled Oroville Gravel 279
179 Cyclic Strength Envelopes for Strength Interpretation II -
Extrapolated Cyclic Test Results 280
180 Representative Relationship Between t/t and Number of Cycles
Required to Cause Liquefaction (Seed et al, 1975) 283
181 Computed Compressive Strain Potentials in Upstream Shell -
Percent 286
CHAPTER VI
182 Oroville Dam Flood Control Outlet Structure Plan and Elevation . . . 292
183 Elevation and Sections 293
184 Maximum Tensile Stresses at time 7.76 sec 295
185 Maximum Tensile Stresses at time 8.46 sec 296
186 Maximum Tensile Stresses at time 7.76 sec. in steel 297
CHAPTER VII
187 Plan and Elevation 352
188 Typical Sections 353
CHAPTER VIII
189 Location Map, Edward Hyatt Powerplant Facilities 390
190 Fish Barrier Dam 391
191 Fish Barrier Dam, Plan and Elevation 392
Figure No. Page
192 Fish Barrier Dam, Section and Details 393
193 Location Map, Thermalito Powerplant^ Forebay^ and Afterbay 394
194 Transverse Section, Units Nos. 3, 4, 5 and 6 396
195 Generator Room, Plan - Elevation 252.0 397
196 Overall view of Edward Hyatt Powerplant Intake Structure 398
197 Transverse Section, Unit No . 1 400
198 Switchyard and General Floor 401
199 230-KV Power Circuit Breakers 404
CHAPTER IX
200 Schematic Diagram of Oroville Complex 410
201 Schematic Diagram of Oroville Dam and Vicinity 411
202 Schematic Diagram of Thermalito Forebay and Vicinity 412
203 Schematic Diagram of Thermalito Afterbay and Vicinity 413
APPENDIXES
A Reports Prepared by the Special Consulting Board and Responses by
by the Department of Water Resources 423
B Acceleration Time Histories and Response Spectra for the August 1,
1975 and September 27, 1975 Recorded Motions on Dam Crest and
Bedrock, in Upstream-Dovmstream Direction. (Figs. B-1 through B-8) 457
C Static Stresses from Static Finite Element Analysis. Figs. C-1
through C-9) 467
D Time Histories and Response Spectra for Reanalysis Earthquake.
(Figs. D-1 through D-6) 483
E Results of Dynamic Finite Element Analyses for Reanalysis
Earthquake 489
Maximum Section ~ Shell K2 max = 350, 200, 130
Element Stresses and Strains (Figs. E-1 through E-18) . . 490
Shear Stress Time Histories (Figs. E-19 through E-39) . . 500
Section 2 — Shell Kn „^^ - 130 - LUSH and QUAD4
I max ^
Element Shear Stresses and Strains (Figs. E-40
through E-45) 521
xxiii
Acceleration Time Histories (Fig. E-46) 525
Section 3 — Shell K2 ^g,^ = 130 - LUSH and QUAD4
Element Shear Stresses and Strains (Figs. E-47
through E-52) 526
Acceleration Time Histories (Fig. E-53) 530
Model Embankment — Shell K2 ^ax ^ ^^^
Effect of Poisson's Ratio on Stresses (Figs. E-54
through E-55) 531
F Embankment Response Model 533
G Cyclic Triaxial Test Summaries of Modeled Oroville Gravel
Tests. (Figs. G-1 through G-68) 541
H Extrapolation of Isotropically-Consolidated Cyclic Triaxial Tests
for Strength Interpretation II. (Figs. H-1 through H-25) 613
I Cyclic Triaxial Test Results for Modeled Oroville Gravel Using
Strength Interpretation II. (Figs. I-l through I-IO) 629
J Procedure for Interpreting Cyclic Triaxial Test Data to Determine
Cyclic Shear Stress on Potential Failure Plane 641
K Cyclic Triaxial Test Results for Modeled Oroville Gravel Using
Strength Interpretation I. (Figs. K-1 through K-IO) 649
L (Available on request later in 1979)
M Embankment Strain Potentials. (Figs. M-1 through M-4) 663
PLATES
(inside rear cover)
Plate 1. Geology of Lake Oroville Area, Butte County, California
Plate 2. Oroville Area Level Net Benchmark Locations
CONVERSION FACTORS
Metric to Customary System of Measurement
Quantity
Length
Volume
Flow
Mass
Velocity
Power
Pressure
Specific
capacity
Concentration
Electrical
conductivity
Temperature
Metric Unit
millimetres (mm)
centimetres (cm) for snow depth
metres (m)
kilometres (km)
square millimetres (mm^)
square metres (m^)
hectares (ha)
square kilometres (km^)
litres (I)
megalitres
cubic metres (m^)
cubic metres (m^)
cubic metres (m^)
cubic dekametres (dam-^ )
cubic hectometres (hm-^)
cubic kilometres (km-^)
cubic metres per second (m-^/s)
litres per minute (l/min)
litres per day (I/day)
megalitres per day (Ml/day)
cubic metres per day (m^/day)
kilograms (kg)
tonne (t)
metres per second (m/s)
kilowatts (kW)
kilopascals (kPa)
kilopascals (kPa)
litres per minute per
metre drawdown
milligrams per litre (mg/l)
microsiemens per
centimetre (//.S/cm)
degrees Celsius ("C)
Multiply by
To get customary equivalent
0.03937
inches (in)
0.3937
inches (in)
3.2808
feet (ft)
0.62139
miles (m)
0.00155
square inches (in2)
10.764
square feet (ft2)
2.4710
acres (ac)
0.3861
square miles (mi^)
0.26417
gallons (gal)
0.26417
million gallons (10^ gal)
35.315
cubic feet (ft^)
1.308
cubic yards (yd^)
0.0008107
acre-feet (ac-ft)
0.8107
acre-feet (ac-ft)
0.8107
thousands of acre-feet
0.8107
millions of acre-feet
35.315
cubic feet per second (ft^/s)
0.26417
gallons per minute (gal/min)
0.26417
gallons per day (gal/day)
0.26417
million gallons per day (mgd)
0.0008107
acre-feet per day
2.2046
pounds (lb)
1.1023
tons (short, 2,000 lb)
3.2808
feet per second (ft/s)
1 .3405
horsepower (hp)
0.145054
pounds per square inch (psi)
0.33456
feet head of water
0.08052
gallons per minute per
foot drawdown
1.0
parts per million
1.0
micromho per centimetre
1 .8 y "C) + 32
degree Fahrenheit ("F)
CHAPTER I
INTRODUCTION
Oroville Dam (Figure 1) is situated in
the foothills of the Sierra Nevada above
the Sacramento Valley. The dam is 8 kilo-
metres (5 miles) east of the City of
Oroville and about 209 kilometres (130
miles) northeast of San Francisco.
On August 1, 1975, at 1320 hours (1:20
p.m.) PDT, an earthquake of Richter Scale
magnitude 5.7 occurred about 12 kilo-
metres (7.5 miles) southwest of Oroville
Dam. During the main event and the many
aftershocks that followed, the Oroville
facilities continued operating without
interruption except for about a 45 minute
shutdown of power generation.
The Oroville earthquake sequence began
with a number of foreshocks on June 28,
1975. Then, on August 1, twenty-nine
foreshocks occurred within 5 hours of
the main shock. The largest of these had
a magnitude of 4.8. Many aftershocks,
the largest of which had a magnitude of
5.1, occurred throughout August, and
scattered shocks continued.
Purpose
Intensive investigations originating from
the August 1, 1975, Oroville earthquake,
were conducted to determine :
1. Geologic and tectonic conditions.
2. Fault mechanism and orientation.
3. Crustal movements.
4. Public safety as it relates to the
Department's facilities.
The results of these investigations are
presented in detail in the following
chapters .
Description of the Oroville Facilities
Oroville Dam and its appurtenances, along
with the Thermalito facilities (Figure 2) ,
comprise a multiple purpose project,
which includes water conservation, power
generation, flood control, recreation.
nc_'p^
Figure 1 . Orovi 1 le Dam
GENERAL
LOCATION
%
WEST ena»<CH
H
T T
LAKE OROVILLE
ELEV. 900'
THERUALITO POWER CANAL y
WESTERN PACIFIC R R
YON CREEK BRIDGE
BIDWELL BAR BRIDGE
FE4THER RIVER
Fish hstcheRY^
AND FISH
BARRIER DAM
•River outlet r
TER' BUTTE CANAL OUTLET
m
VERLOOK V'^ eiDwELL CANYON
\^2
^ENTERPRISE BRIDGE
''SflDOLE 0AM
■/
kilometres
5
J I I I I
-OROVILLE EARTHQUAKE
EPICENTER M = 5.7
AUGUST I, 1975
Figure 2. Location Map, Oroville Facilities
and fish and wildlife enhancement. The
lake stores winter and spring runoff,
which is released into the Feather River
as necessary to supply project needs and
commitments . The pumped-storage capa-
bility of the Oroville facilities permits
maximum use of peaking capabilities and
increases the value of power produced by
the releases.
Water releases from Edward Hyatt Power-
plant are largely diverted from the
Feather .River at the Thermalito Diversion
Dam (Figure 3) , a concrete gravity struc-
ture with a radial gated crest section.
These diversions pass through the Therma-
lito Power Canal and Thermalito Forebay
(Figure 4) , through Thermalito Powerplant,
and into Thermalito Afterbay. The Therma-
lito Diversion Pool, Power Canal, and
Forebay have a coimion water surface to
accommodate flow reversals for the pumped-
storage operation. Thermalito Afterbay
(Figure 5) stores the plant discharges
for the pumped-storage or conventional
operation and reregulates flow for \ini-
form return to the Feather River.
Migrating salmon and steelhead blocked
by the Oroville Complex are diverted
from the river into the Feather River
Fish Hatchery at the Fish Barrier Dam,
located 0.8 kilometre (0.5 mile) down-
stream from the Thermalito Diversion Dam.
The Investigating Organization
On August 8, 1975, the Department of
Water Resources convened its Consulting
Board for Earthquake Analysis to review
the general post-earthquake situation
and the preliminary data assembled. On
September 11 and 12, 1975, a Special
Consulting Board for the Oroville Earth-
quake, composed of the members of the
Consulting Board for Earthquake Analysis
and additional engineering consultants
in the field of design and construction
of dam and reservoir projects, was con-
vened by the Department to review the
Department's programs for data collec-
tion and evaluation of structural
seismic safety.
The Special Consulting Board for the
Oroville Earthquake consisted of the
following members :
George W. Housner, Chairman
Clarence R. Allen
John A. Blume
Bruce A. Bolt
Wallace L. Chadwick
Thomas M. Leps
Alan L. O'Neill
Philip C. Rutledge
H. Bolton Seed
With recommendations from the Special
Consulting Board, several earthquake-
related investigations were undertaken
by the Department. These include:
1. Geologic studies and mapping of
the epicentral area and the causa-
tive fault.
2. Seismological studies dealing with
the earthquake sequence and fault
plane resolution.
Figure 3- Thermalito Diversion Dan
Figure k. Thermal! to Forebay Dam
3. Determination of the seismic safety
of project structures under loading
of the Reanalysis Earthquake
selected for this area.
4. Surveys of the area.
5. Evaluation of the existing seismic
instrumentation monitoring system.
The Special Consulting Board was recon-
vened on November 22 and 23, 1976, to
review the progress of the investiga-
tions and provide recommendations. On
September 28 and 29, 1978, the Special
Consulting Board was convened to review
those completed reports on the investiga-
tions and reanalysis of the Oroville
facilities prior to their being published
in this bulletin. Progress of the
uncompleted reports was also reviewed.
To meet regular State and Federal safety
review requirements for the Oroville-
Thermalito facilities, the Special Con-
sulting Board was requested to be the
Department's consultant for these
requirements .
Reports prepared by the Special Consul-
ting Boards and Department ' s responses
are included in Appendix A.
Reanalysis of Project Structures for
Earthquake Safety
The performance of State Water Project
facilities during the August 1975 earth-
quake sequence demonstrated their ability
to withstand this seismic loading. Only
minor superficial damage was sustained
by some of the secondary structures.
The Department's Bulletin 203 (April
1977) , Performance of the Oroville Dam
and Related Facilities During the
August 1, 1975 Earthquake, documents
the performance of the Oroville complex
Figure 5- Thermal ito Afterbay Dam
during the main event and succeeding
aftershocks.
The Special Consulting Board reviewed
the seismic environment of the Oroville
facilities and recommended an earthquake
motion be developed for reevaluation of
the Oroville-Thermalito structures that
has a magnitude of 6.5 producing a peak
acceleration of 0.6g. Detailed develop-
ment and characteristics of this
Reanalysis Earthquake are described in
Chapter V ,
A program for dynamic structural analy-
sis of critical structures was imple-
mented in cooperation with Professors
H. Bolton Seed, A. K. Chopra, and Edward
L. Wilson of the University of California,
Berkeley. The critical structures to be
reanalyzed are: Oroville Dam, Oroville
Dam Spillway (flood control outlet
structure) , Thermalito Diversion Dam,
Thermalito Powerplant Headworks, Therma-
lito Forebay Dam, and Thermalito Afterbay
Dam. Dynamic strengths of the material
in Oroville Dam were determined by large-
scale laboratory testing conducted by
the University of California. Explora-
tion and soils testing for the Thermalito
Forebay and Afterbay Dams were conducted
by the Department of Water Resources.
Summary of Conclusions
and Recommendations
The following are conclusions and recom-
mendations from the chapters in this
Bulletin.
Geological Investigations (Chapter II)
1. The August 1, 1975, Oroville earth-
quake was accompanied by movement
on the previously unrecognized
Cleveland Hill Fault. A linear
zone of discontinuous ground crack-
ing developed along the fault about
7 kilometres (4.3 miles) east of
the main shock epicenter.
2. Initial length of ground rupture
on the Cleveland Hill Fault was
about 1.6 kilometres (1.0 mile).
Over a period of about 12 months
the ground cracking extended pro-
gressively to the north, reaching
a total length of 8.5 kilometres
(5. 3 miles) .
3. Offset along the fault was greatest
in the southern segment, where the
original cracking occurred. Offset
increased with time; movement
amounted to about 50 millimetres
(2 inches) vertical displacement
and 25 millimetres (1 inch) hori-
zontal extension.
4. The Cleveland Hill Fault was not
encountered by trenching or geo-
physical investigation north of
Mt. Ida Road. Aftershock hypo-
centers projected up a calculated
fault plane indicate the fault at
the ground surface trends into
Bidwell Canyon and that it may pass
beneath Oroville Dam at depth.
5. Trenching across the Cleveland Hill
Fault by Department of Water
Resources and others provides
evidence for multiple small fault
displacements during the past
100,000 years. These displace-
ments would likely have produced
earthquakes similar to the 1975
Oroville event.
5. Three major lineament- fault zones,
the Paynes Peak, Swain Ravine, and
Prairie Creek, have been delineated
in the area by geologic studies .
These lineament-fault zones are
complex bands of discontinuous, inter-
twined, steeply dipping faults which
were formed during Mesozoic or ear-
lier time under the influence of a
different tectonic stress regime
that exists today. The Cleveland
Hill Fault is within the Swain
Ravine Lineament fault zone.
7. Most Cenozoic fault movements in
the Sierran foothill belt are caused
by east-west extensional stresses
reactivating pre-existing Paleozoic
and Mesozoic faults such as those
comprising the lineament-fault zone.
8. Historic (Cenozoic) faulting and
historic earthquake records in the
foothill region demonstrate that
the current and long-range level of
seismic activity is one of low- to
moderate-magnitude earthquakes at
relatively long recurrence intervals,
occasionally resulting in minor
ground rupture and offset.
9. Nothing was seen in this geologic
study to indicate that earthquakes
greater than Richter Magnitude 6.5
should be expected in the Oroville
area.
10. Maximum offset that should be anti-
cipated from another Oroville-type
earthquake is estimated to be 50
millimetres (2 inches) of vertical
displacement and 25 millimetre (1
inch) horizontal extension. For a
somewhat larger event displacement
might be several times larger than
these values, along north-south
trending faults .
H- The evidence available does not
indicate a causal relationship
between Lake Oroville and the earth-
quake, but the possibility cannot
be eliminated conclusively at this
time.
Seismology (Chapter III)
Since August 1, 1975, a correlation is
not indicated between the Lake Oroville
water surface variations and the rate
of occurrence of Oroville aftershocks.
Within the boundary of the aftershock
zone north of 39 26 'N latitude, vertical
cross-sectional plots indicate that the
Cleveland Hill Fault is a single, well
defined break, dipping to the west at
about 60 with the horizontal and with a
near north-south strike. Vertical cross-
sectional plots south of 39 26 'N indicate
that the fault breaks along more than one
plane.
Vertical and Horizontal Geodesy
(Chapter IV)
Vertical Crustal Movements
The following conclusions are based on
free adjustment holding the elevation of
OM-27 fixed (1967 USC&GS adjustment) and
therefore all elevations differentials
are relative to OM-27.
1. Based on the preearthquake datum of
1967, the greatest elevation differ-
ential was only 63 millimetres (0.207
foot) on line Olive during the ten-
year epoch (1967-1977) .
2. The August 1, 1975, Oroville earth-
quake is associated with minor sub-
sidence in the Oroville area, mainly
south and southwest of Lake Oroville.
3. Most of the subsidence associated
with the August 1, 1975, Oroville
earthquake was measured between late
August 1975 to October 1976.
4. The elevation differentials show
movement of the fault zone that
passes through the level lines
Cleveland Hill and Mission Olive
(ground cracking was evident before
the lines were established) . A fault
zone may pass through the survey line
Miners Ranch south of Lake Oroville;
however, no ground cracking was
found there.
5. Minor subsidence of less than 25
millimetres (0.082 foot) has been
measured adjacent to Oroville Dam
and Lake between 1967 to 1977 due to
all causes.
Horizontal Crustal Movements
1. All computed horizontal movements are
minor and in many cases within the
accuracy of the existing surveys and
computations .
2. The August 1, 1975, Oroville earth-
quake did not cause sufficiently
large horizontal movements that could
be reliably measured and calculated
within the Lake Oroville Monitoring
Network .
Oroville Dam Evaluation of Seismic
Stability (Chapter V)
1. The seismic stability of Oroville
Dam was investigated for the Reanal-
ysis Earthquake of Richter Magnitude
6.5, at a hypocentral distance of
5 kilometres (3 miles) from the dam,
and producing the following ground
motion characteristics at the base
of the dam:
maximum acceleration
predominant period
duration
acceleration time
history
0.6g
0.4 seconds
20 seconds
modified Pa-
coima plus
modified Taft
2.
It was concluded that this ground
shaking was more severe than any
future shaking likely to affect the
dam.
Using "best judgment" choices for
input soil properties and conditions,
relatively small embankment deforma-
tions were estimated by the seismic
evaluation procedures . It is con-
cluded that Oroville Dam would per-
form satisfactorily if subjected to
the Reanalysis Earthquake.
Oroville Dam Flood Control Outlet
Structure (Chapter VI)
The investigations performed indicate
that when the Oroville Flood Control
Outlet Structure is subjected to the
Reanalysis Earthquake ground motion it
is stable, and that expected compressive
and tensile stresses are within the
allowable limits established for the
structure .
Based on results of dynamic analyses
and available data for concrete strength,
it is concluded that Thermalito Diver-
sion Dam should be able to resist the
stresses expected during the earthquake
(Reanalysis Earthquake) ground motion
specified by the State Department of
Water Resources.
Reappraisal of Secondary Structures
(Chapter VIII)
Fish Barrier Dam - A review of the orig-
inal design of this dam indicated maxi-
mum compressive and tensile stresses of
approximately 120 psi and 10 psi respec-
tively. A check of stability using a
pseudostatic analysis and seismic coeffi-
cients of 0.25 and 0.6 indicated a shear
friction factor of safety in excess of 9.
Based on this finding, no additional
seismic analysis is recommended for the
Fish Barrier Dam.
Edward Hyatt Powerplant - The powerhouse
substructure has been reviewed using a
comparative pseudostatic analysis of
previously designed powerhouse substruc-
tures. Based on this comparison, it has
been determined that this substructure
would be capable of resisting the forces
induced by a 0.25g peak ground accelera-
tion; therefore, no modifications are
required.
Modifications will be made to improve
the seismic resistance of powerhouse
superstructure components as necessary.
Thermalito Powerplant - The powerhouse
substructure has been reviewed using a
comparative pseudostatic analysis of
previously designed powerhouse substruc-
tures. Based on this comparison, it has
been determined that this substructure
would be capable of resisting the forces
induced by a 0.25g peak ground accelera-
tion; therefore, no modifications are
required .
Thermalito Diversion Dam (Chapter VII)
Conclusion by Dr. A. K. Chopra:
Modifications will be made to improve
the seismic resistance of powerhouse
superstructure components as necessary.
Miscellaneous Structures - Damage that
may occur to the miscellaneous structures
are not considered to be a threat to
public safety and property. For the
purpose of the seismic reevaluation
these structures are classified as
noncritical.
Bridges - Bridge components that will
not sustain the forces generated by a
0.25g peak ground acceleration will be
modified to strengthen their seismic
resistance.
Switchyards - Based on the considera-
tion that failure of electrical equip-
ment in the Edward Hyatt or Thermalito
Powerplant switchyards does not pose a
threat to public safety or property, the
switchyards are classified as noncritical
elements of the Oroville Complex.
Contingency Plan for Seismic Emergencies
(Chapter IX)
The contingency plan is attentive to
established Division Policy; it provides
for detection, notification, and response
to seismic events. The plan also includes
a list of operational facilities and
features along with criteria that must be
met before returning to preearthquake
operating status .
Department's Findings
Based on the preceding conclusions from
the investigations completed to date,
the Department concludes that these facil-
ities do not pose a threat to public
safety.
Uncompleted Reports
The reanalysis of the Thermalito Power-
plant Headworks and the Thermalito Fore-
bay and Afterbay Dams has not been
completed. Dr. A. K. Chopra (the
Department's consultant) is currently
reanalyzing the Thermalito Powerplant
Headworks. The Department is continuing
with the reanalysis of the Thermalito
Forebay and Afterbay Dams. Investiga-
tions of the Bidwell Canyon Saddle Dam
and the effect of fault movements with
respect to the Oroville-Thermalito facil-
ities will also be completed. These
reports are planned for completion early
in 1979 and publication by mid-1979.
Safety Review Requirements
The completion of the investigations and
reanalysis of the Oroville facilities
with concurrence by the Special Consul-
ting Board fulfills the following two
safety requirements:
1. The five-year Federal Energy Regu-
latory Commission's Part 12 Safety
Inspection Report.
2. The five-year Department of Water
Resources, Division of Safety of
Dams ' safety review under the regu-
lations of the California Administra-
tive Code, Title 23, Article 4,
Sections 340-343.
Report of the Special Consulting Board
For the Oroville Earthquake
November 15, 1978
(see next page)
15 November 1978
Report of the Special Consulting Board for the Oroville Earthquake
Mr. Howard H. Eastin, Chief
Division of Operations and Maintenance
Department of Water Resources
P.O. Box 388
Sacramento, California, 95802
At meetings on September 28 and 29, 1978, of the Special Consulting
Board for the Oroville Earthquake, staff members of the Department of Water
Resources made presentations relative to the Department's draft of its
report, "August 1, 1975, Oroville Earthquake Investigation - Bulletin
203-78." The Board has also reviewed chapters of the draft prior to the
meeting. At the conclusion of the meetings, the Board was asked to respond
to the following questions relating to the content of the Oroville Earthquake
Investigation report. Our responses are presented below.
Question No. 1 . Does the Board concur with the conclusions and the
recommendations set forth in the Summary of Conclusions and Recommendations?
Response. The Board has reviewed the draft of the chapters of Bulletin
203-78 and has heard the presentations of the staff members, and has reviewed
the "final Draft Chapter 1" which contains the Summary of Conclusions and
Recommendations.
The Board concurs with the conclusions and the recommendations set forth
in the Summary of Conclusions and Recommendations in the October 24, 1978,
"final draft" of Chapter 1.
Question No. 2. Does the Board agree that the Oroville Division's
critical structures (except Thermal i to Forebay and Thermal i to Afterbay Dams)
would perform adequately with respect to public safety during the adopted
earthquake ground motions?
Response. The Board agrees that the critical structures (except
Thermal ito Forebay and Afterbay Dams which have not yet been analyzed) would
perform adequately with respect to public safety if subjected to the adopted
earthquake ground motions.
Question No. 3. Does the Board have any comments on the studies completed
to date for the seismic stability of Thermal ito Forebay and Afterbay Dams?
Response. The Board does not have any comments except to urge completion
of the studies at an early date.
Question No. 4. The Department intends to publish the results of the
Thermal ito Power Plant - Headworks, Seismic Evaluation, and Thermal ito Forebay
and Afterbay, Evaluation of Seismic Stability, reports next year, possibly as
Bulletin No. 203-79. Does the Board consider another meeting necessary or
could the Board's review, comments and report be handled by correspondence?
Response. The Board feels that another meeting would be desirable at
which staff members would present the results of the analyses and respond to
questions from the Board.
Question No. 5. Does the Board have any other comments or recommenda-
tions to make at this time?
10
-3-
Response.
a. The Board recommends that in Chapter 2-Contingency Plan for Seismic
1/ 2/
Emergencie^the criteria for notification given on page 5 "5e revised to read
base
that O.lg recorded at the e^est of Oroville Dam will replace the 3.0 Richter
Scale criteria for notification, and 0.15g will replace the 4.0 Richter Scale
criteria. It is also recommended that Annual Earthquake Drills be held so
that personnel will be prepared to act in the event of an actual earthquake.
3./
b. With reference to Chapter 5, the Board recommends that DWR request
NCAA to perform a precise level survey from a known, stable benchmark to
benchmark OM 27, as this benchmark is a key element in the geodetic survey
at Oroville Dam.
II
c. With reference to Chapter 5, the Board recommends that resurveys
be made at 5 year intervals, or after significant earthquakes, to monitor
crustal movements that might have taken place.
The Board was favorably impressed by the investigations and analyses
carried out by the Department, and commends the Department for the
diligence and thoroughness of its work.
1_/ Chapter IX in this bulletin.
2/ See page ^7 in this bulletin.
.2/ Chapter IV in this bulletin.
11
Respectfully Submitted,
George W. Ho\lsi>er
C. R. Alren
J^
^ .^ .^ r'^/-
John A. Blume
rhu^^ Qy/^^J^
Bruce A. Bolt
sMi^
T. M. Laps
Alan L. O'Neill
Philip a. Rutledge /
^. (i^^Uo^ <^^^'<^
H. Bolton -S€ed »"
^ \ r -, «„ — I )iu^,^,,-;'^i, 1-' — ' '
"Wallace h, (JhaawicK
12
REVIEW BY THE DIVISION OF MINES AND GEOLOGY
The Department requested the Department of Conservation,
Division of Mines and Geology to review the final draft of
Bulletin 203-78
The response from the Division of Mines and Geology
on Bulletin 203-78 follows.
13
State of California The Resources Agency
Memorandum
To : Clifford V. Lucas, Chief Civil Maintenance Branch Date: December 22, 1978
Division of Operations and Maintenance
Department of Water Resources
]h]6 9th Street
Sacramento, California 9581^*
From Department of Conservation
Division of Mines and Geology
1416 -9th Street, Sacromento 95814
Subject: Review of DWR Bulletin 203-78 Final Draft
This is our response to your request of December 11 that the Division of
Mines and Geology provide review of final draft of DWR Bulletin 203-78.
Our commentary is limited to one observation in Chapter IV, Sei smology . 1/
2/
The conclusion (page 5)~ that there is no correlation between water levels
and the rate of earthquakes does not consider the strengths of the earthquakes,
but is based on a count of events regardless of magnitude. When the strengths
of the earthquakes are considered, the resulting pattern of seismic strain
released might be related to water levels. Most of the seismic strain
appears to be released following episodes of filling, and very little strain
release appears to occur during the actual filling.
We appreciate the opportunity to comment on this useful publication.
nes F. Davis
State Geologist
cc: Pri sci 1 la C . Grew
1_/ Chapter III in this bulletin,
2/ Page 12^4- in this bulletin.
14
CHAPTER II
GEOLOGIC INVESTIGATIONS
On August 1, 1975, a strong earthquake
occurred near Oroville, California. The
earthquake sequence began June 28, 1978,
with the occurrence of several fore-
shocks; the largest of these foreshocks
was magnitude 3.8. From July 8 through
July 31, only five foreshocks occurred,
giving the appearance that earthquake
activity was ceasing. Then on August 1,
twenty-nine foreshocks, the largest of
which was magnitude 4.8, occurred within
five hours prior to the magnitude 5.7
main shock at 1320 hours Pacific day-
light time.
The hypocenter for the main shock of the
Oroville earthquake series was approxi-
mately 1 km (0.6 mi) east-northeast of
Palermo at a depth of 8.8 km (5.5 mi).
Fault movement ruptured the ground
approximately 7 km (4 mi) east of
Palermo. This ground rupture is called
the Cleveland Hill Fault.
Prior to the 1975 earthquake, seismic
hazard was not regarded as being great
in the Oroville area. It was recognized
that earthquakes do occur in the sur-
rounding region, and that the largest
recorded earthquake was a magnitude 5.7
in 1940 north of what is now Lake
Oroville. Fault movements were not con-
sidered likely to occur along faults in
the area. Because fault movement occur-
red where no fault was suspected before
the Oroville earthquake, it was obvious
that existing geologic information did
not identify potentially active faults
in the Oroville area. Therefore, geo-
logic investigations were started
immediately.
PURPOSE OF THE INVESTIGATION
The purposes of geologic investigations
were threefold: (1) to understand the
geologic and tectonic conditions which
caused the Oroville earthquake; (2) to
evaluate any potential hazards; and
(3) try to determine if Oroville
Reservoir caused the earthquake.
The original thrust of investigation was
to determine if the Cleveland Hill Fault,
movement along which caused the 1975
earthquake, was an old or new fault, and
if it extended northward to endanger
Department facilities in the Oroville
area. The investigations later were ex-
panded to cover the surrounding area.
PREVIOUS WORK
The area geology was first mapped in the
late 1800 's by Waldemar Lindgren and
Harry Turner. Their work was published
as the Bidwell Bar folio (Becker and
others, 1898) and the Smartsville folio
(Lindgren and Turner, 1895) of the U. S.
Geological Survey Atlas of the United
States series. These works include the
Bangor, Oroville Dam, and Berry Creek
quadrangles which comprise half of our
study area (Figure 6) .
The northern Sierra foothills were again
the center of detailed mapping in the
1950 's for studies of the Merrimac plu-
ton (Hietanen, 1951) and the Bidwell Bar
area (Compton, 1955). In 1955, Robert
Creely completed a doctoral mapping
thesis of the Oroville 15-minute quad-
rangle, which includes the Hamlin Canyon
Cherokee, Shippee, and Oroville
7-1/2 minute quadrangles. Creely 's
work was published in 1965 as Bulletin
184 by the California Division of Mines
and Geology.
Areas of the Oroville, Oroville Dam,
Cherokee and Berry Creek quadrangles
were mapped in detail during the late
1950 's and early 1960 's by geologists
from the Department of Water Resources
for studies associated with the con-
strutruction of Oroville Dam and related
15
APPROXIMATE LIMIT OF
RECONNAISSANCE MAPPING
Lake
A I manor
Figure 6. Location map of six-quadrangle study area,
16
facilities. Mapping to the south of
the area by other individuals and
agencies includes preliminary work in
the Bangor quadrangle (Quintin Aune,
unpub. data), graduate theses in the
Smartville area (Buer, 1978; Costas
Xenophontos, in progress), a regional
study by the U. S. Army Corps of
Engineers (1977) for the proposed Parks
Bar Dam on the Yuba River, and fault
studies made by Woodward-Clyde
Consultants for both the U. S. Army
Corps of Engineers and Pacific Gas and
Electric Company. Additionally,
Woodward-Clyde Consultants (1977) con-
ducted a regional fault investigation
in the northern foothill belt for the
U. S. Bureau of Reclamation's Auburn
Dam project on the American River.
Numerous other references contribute to
a general understanding of structural
and stratigraphic relationships in the
Oroville area. Some of these include
the Geologic Map of California, Westwood
Sheet (Lydon and others, 1960), Geology
of the Richardson Springs quadrangle
(Burnett and others, 1969), and work by
Hietanen (1973a, 1976, 1977). An under-
standing of the importance of faulting
and some knowledge of its history and
nature is provided in the works of
Clark (1960, 1964, 1976), Cebull (1972),
Duf field and Sharp (1975), and
Schwieckert and Cowan (1975). Models
and evidence for plate tectonic evolu-
tion of the area are adopted and modi-
fied after Hamilton (1969) , Moores
(1972), Schweickert and Cowan (1975),
and Schweickert (1976).
SCOPE OF THE INVESTIGATION
Several types of imagery were used to
find major structural trends and linea-
ments prior to field mapping. These
included satellite imagery, high-
altitude black-and-white and infrared
photographs , radar imagery (SLAR) , and
low-altitude black-and-white and color
photographs.
Satellite imagery was from the ERTS
(now LANDSAT) program of the U. S.
Government (NASA) . Radar imagery was
obtained from Woodward-Clyde Consultants.
High- and low-altitude photography is
comprised of four sets flown for the
Department of Water Resources, including
a set of low-altitude low-sun-angle
photographs, and one set from the
U. S. Forest Service.
Detailed geologic mapping was done in
the Palermo, Bangor, Oroville, Oroville
Dam, Cherokee and Berry Creek 7-1/2 min-
ute quadrangles (Figure 6). Reconnais-
sance geologic mapping was done in the
remainder of the study area, extending
northwest some 70 km (43 mi) from
Oroville.
Detailed mapping was generally done on
a 7-1/2 minute quadrangle base. Where
more detail was desired, mapping was
done on quadrangles enlarged to 1:12,000.
Areas mapped in detail were covered on
foot; samples of rock were collected,
photographed or sketched where appropri-
ate, and mapped. Most of the rock units
were sampled and petrographic analyses
were made by Costas Xenophontos of the
University of California at Davis.
Reconnaissance mapping was done on
7-1/2 minute topographic base maps wher-
ever possible. Much of the northern
study area was mapped on preliminary
topographic maps received from the U. S.
Geological Survey. Areas along photo
lineaments and faults indicated on the
State geologic maps were checked in de-
tail. In other areas we relied on pre-
vious works and field reconnaissance.
Mapping began in May 1976, and continued
until May 1978. A total of 55 work
months went into field work and report
writing. The majority of mapping was
done by Department of Water Resources
geologists; three geology graduate stu-
dents from the University of California
at Davis assisted during July and
August 1977.
Subsurface information was used whenever
and wherever possible to map rock units
and, especially, to aid in tracing faults
17
J
r
• •••••• A^ A
• • • • /f %• A • 3«$
0 10 20 30 40
U ---*
SACRAMENTO
MAGNITUDE
0 5.0 - 6.0
0 4.0 - 4.9
• 3.0 - 3.9
• 2.0 - 2.9
A NOT KNOWN
5 (number denotes multiple epicenter)
Lake
Tahoe
39°-v
vX
Figure 7- Historic earthquakes within a 100-kilometre (62-mile) radius
of Orovi lie.
18
beyond surface exposures. Subsurface
information was derived from exploratory
trenches, road cuts, railroad cuts and
utility trenches; existing tunnel logs,
well logs, test boring logs, mining re-
ports and Department of Water Resources
design and construction reports were
also reviewed. Geophysical methods were
used to try to trace the Cleveland Hill
Fault beyond the northernmost ground
cracks.
Exploratory trenches in this study in-
cluded 17 by the Department of Water
Resources in the Oroville-Bangor area
(trench logs, page 103 ff.) and several
others by Pacific Gas and Electric
Company, U. S. Army Corps of Engineers
and the U. S. Bureau of Reclamation.
The latter agencies were studying fault-
ing in the Sierran foothills from Sonora
to Oroville. Woodward-Clyde Consultants
were involved as consultants to these
three agencies.
Trenches by the Department of Water
Resources and other agencies were pri-
marily used to explore suspected faults.
Many were cut across surface cracks
shortly after the August 1, 1975, earth-
quake. Seismic and resistivity surveys
were used by Department of Water
Resources geologists, assisted by Elgar
Stevens of the Department of Transporta-
tion, in attempts to trace faulting asso-
ciated with surface cracking.
Tunnel logs reviewed include tunnels 1
through 5, Western Pacific Railroad
relocation by the Department of Water
Resources. Logs for Miners Ranch and
Kelly Ridge tunnels by Bechtel Corpora-
tion for Oroville-Wyandotte Irrigation
District were also reviewed.
The area around Oroville Reservoir and
south to Wyandotte was surveyed immedi-
ately after the August 1, 1975, earth-
quake by teams from the Department of
Water Resources and the U. S. Geologi-
cal Survey. It was hoped that precise
leveling surveys across the Cleveland
Hill Fault would indicate the sense of
movement on this structure.
The Department of Water Resources survey
team ran additional first-order leveling
surveys at regular intervals. Changes
in elevation were contoured by computer
and compared with geological and seis-
mological data collected by the Depart-
ment of Water Resources staff.
Most precise leveling surveys around
Oroville post-date the August 1975,
earthquake. A comparison of August 1975,
first-order leveling data with third-
order leveling data compiled in the
1940' s would be the closest approximation
of crustal movements from the Oroville
earthquake.
SEISMIC HISTORY
Epicenters for earthquakes occurring in
the Oroville area prior to 1934 are esti-
mated from newspaper accounts and reports
by local residents. After 1934, epicen-
ters in the area have been instrumentally
determined. Historic seismicity in the
Oroville area from 1851 to 1975 is shown in
Figure 7 with a few recent earthquakes,
providing more reliable data, indicated
by their date above the epicentral
location.
Numerous low- to moderate-magnitude
earthquakes have occurred in the northern
Sierra Nevada in historic time (Townley
and Allen, 1939; Wood and Heck, 1951).
The most significant event affecting the
Oroville area occurred near Virginia
City, Nevada on December 27, 1869. An-
other earthquake shook the Oroville re-
gion on January 24, 1875, and is believed
to have originated from movement of the
Mohawk Valley Fault (Wolfe, 1967) loca-
ted approximately 70 km (43 mi) to the
northeast; reinterpretation of this
earthquake suggests it was located south-
west of Oroville (Paul Morrison, person,
commun., 1978).
An earthquake on February 8, 1940, cen-
tered 54 km (34 mi) north of Oroville,
is comparable in magnitude to the 1975
Oroville event. Seismic monitoring was
19
Figure 8. Aftershock locations of the Oroville earthquake.
The envelope encloses 90 percent of the epicenters.
20
not good in 1940 and data on the earth-
quake are poor. A recent reassessment
of these data shifted the epicentral
location 40 km (25 mi) and changed the
estimated magnitude from 6.0 to 5.7
(Morrison, 1974, p. 8). The epicenter
does not fall on any known fault, and
no fault plane solution is obtainable
from the seismic data.
The May 24, 1966, "Chico" earthquake
(Figure 7) is unique for this area be-
cause adequate data were obtained to
calculate a fault plane solution. The
timing of this earthquake coincided with
a crustal determination experiment using
a subsurface explosion off the Northern
California coast. This magnitude 4.6
earthquake had a focal depth of 21 km
(13 mi) and provided a fault plane solu-
tion for a N30W strike and a 65 degree
northeast dip, with dominant right-
lateral movement (Lomnitz and Bolt,
1967).
THE 1975 EARTHQUAKE SERIES
Foreshocks of the Oroville earthquake
began June 28, 1975. Fourteen foreshocks
with magnitudes from 2.1 to 4.7 occurred
prior to the main shock at 1320 hours
Pacific daylight time, on August 1, 1975.
The main shock had a Richter magnitude
of 5.7 and was centered about 1 km
(0.6 mi) northeast of Palermo and 12 km
(7.5 mi) south of Oroville Dam. The
focal depth was 8.8 km (5.5 mi).
Oroville earthquake aftershocks, includ-
ing more than 5,600 recorded events,
were still occurring in June 1978. Fre-
quency of aftershocks has decreased
steadily, from over 700 per day in early
August 1975, to ten per month in
June 1978.
The region of aftershocks increased in
size for several months after the
August 1, main shock (Lester and others,
1975); the most rapid increase was dur-
ing the first week of this time period.
Surface area envelopes of aftershock
epicenters are ellipsoidal with the elon-
gated axis oriented north-south. This
pattern matches the north-south trend of
the Cleveland Hill Fault in the subsur-
face. Initially the aftershock zone
expanded to the east, with the shocks
occurring at shallower depths. Then
the zone expanded both to the north and
to the south, with the final expansion
being to the north. An envelope con-
taining the majority of aftershocks is
shown in Figure 8. Aftershock epicen-
ters have occurred as far north as
Oroville Dam, and a few have occurred
east of the Cleveland Hill Fault rupture.
Depths of aftershocks were 8 to 9 km (5
to 6 mi) on the west and became shal-
lower toward the east . A fault plane
solution shows the Cleveland Hill Fault
strikes N25W to N5E (Beck, 1976; Clark
and others, 1976; Morrison and others,
1976), dips 60 degrees west and passes
5 km (3 mi) beneath Oroville Dam (Lahr
and others, 1976). First motion fault
analyses indicate a dip-slip movement
with the west side down; this movement
indicates normal faulting and tensional
deformation.
Property damage caused by the earthquake
consisted of fallen plaster, toppled
chimneys, broken windows, items thrown
from shelves, etc. Major damage included
homes shifted off their foundations and
an older brick home that was damaged be-
yond repair. Damage to State facilities
was very minor and consisted mostly of
non-structural plaster cracks in build-
ings and some settlement and cracking
of uncompacted fill embankments around
Thermalito Afterbay.
Several changes in ground water occurred
after the earthquake: (1) a few wells
and springs went dry and others tempor-
arily increased their flow, and (2) new
springs appeared where none had been
prior to the earthquake.
21
Figure 9. Locations of the Cleveland Hill and Mission Olive crack zones and
sites of Department of Water Resources exploration trenches
22
GROUND CRACKING
Investigations were made of reported
ground cracking during the first few
days after the earthquake. Most cracks
observed were lurch or settlement indu-
ced. Two areas of cracking did emerge
as worthy of further investigation.
These two zones are the "Palermo crack
zone", trending northwest through the
epicentral area, and cracking along
Cleveland Hill Fault.
The "Palermo crack zone", the western-
most crack zone, consisted of discontin-
uous cracks at a number of locations.
Collectively, the crack sites are align-
ed in a linear northwest trend. The
crack zone lines up with the Prairie
Creek Lineament to the southeast . The
entire crack zone extended from 3 km
(1.9 mi) south of Palermo to just south
of Oroville for a total length of about
9 km (5.6 mi). Additional cracking,
discovered later during the investiga-
tion, appeared to have occurred a con-
siderable time after the main earthquake.
The linear trend of the Palermo crack
zone gave rise to the suspicion that the
disturbance occurred along a fault zone,
subsequent investigations did not reveal
faulting but it is not really clear
whether or not a subsurface fault extends
northwest along the trend of the Prairie
Creek Lineament.
Cracking near Cleveland Hill (Figure 9)
was first detected on August 6, 1975.
Cracking occurred in an en echelon pat-
tern and formed a discontinuous zone 1
to 7 m (3 to 22 ft) wide and 1.6 km
(1 mi) long. In 6 weeks some cracks
widened to 40 mm (1.6 in) and showed up
to 30 mm (1.2 in) of downdrop on the
west side (Figures 10 and 11) . The
cracks became more pronounced with time
and some were still visible 3 years after
the main shock.
Early in October 1975, two approxi-
mately parallel crack zones were found
north of Cleveland Hill. These cracks,
named the Mission Olive crack zone
(Figure 12), are 400 m (1,300 ft) apart
and extend discontinuously for about
2 km (1.25 mi) to the north. The Mission
Olive crack zone initially was seen in
the asphalt paving on Mission Olive Road
and Foothill Boulevard (Figure 9). The
, ^.<
Figure 10. Ground cracking that resulted
from the August 1, 1975, Oroville
earthquake.
Figure 11. Close-up view of a ground
crack on southwest slope of Cleveland
Hill.
23
Figure 12. Locations of ground cracking from the Oroville earthquake and
major photo lineaments in the southern study area
24
cracks definitely were not present in
August 1975, when all paving between
Cleveland Hill and the reservoir was
inspected.
In February 1976, another 182 m (600 ft)
of cracking was found in a pasture 3 km
(1.9 mi) south of Bidwell Canyon Saddle
Dam. This cracking was not present in
October 1975, when the site was selected
for an exploration trench on the Swain
Ravine Lineament by Department of Water
Resources geologists. In August 1976,
another 116 m (380 ft) of cracking was
found north of the pasture in an olive
orchard. The crack zone now reached
nearly to Mt. Ida Road which is 2.1 km
(1.3 mi) south of Bidwell Canyon Saddle
Dam (Figure 13) .
In February 1977, an additional short
segment of ground cracking was found
along the Swain Ravine Lineament 1.8 km
(1.1 mi) south of the southern end of the
Cleveland Hill cracks. This is the only
instance of crack zone development pro-
gressing southward. Periodic field
checks after discovery of the last crack
zone have shown no new cracking to the
north or south.
Initial cracking from the Oroville
earthquake occurred only along the Swain
Ravine Lineament west of Cleveland Hill.
During the 12-month interval following
the main shock, cracking propagated sev-
eral kilometres northward. Timing of
northward extensions of cracking is not
precisely known and therefore cannot be
related to specific aftershocks; exten-
sion of cracking is probably related to
continuing readjustment on the fault.
Overall extent of cracking is 8.5 km
(5.3 mi) and the collective length of
individual zones is 5.3 km (3.3 mi).
Displacement on individual cracks was
most pronounced in areas of initial
cracking.
OroviHe Dam
Saddl® Oam»
Figure 13- Aerial north view of northern limit of ground cracking (Cleveland
Hill Fault) just west of Wyandotte Miners Ranch Road. These cracks project
toward the Bidwell Canyon Saddle Dam.
25
In addition to the progressive increase
in the areal extent of cracking with
time, displacements along the cracking
also increased as time passed. The
increase in displacement was discernible
by eye, particularly in the first few
months following the earthquake. The
most pronounced visual impact of dis-
placement increase was near Cleveland
Hill where ground cracking was first
discovered. Here a noticeable vertical
displacement (down to the west) developed
with time and the cracks became wider.
The U. S. Geological Survey installed
five arrays of survey monuments along
the southern crack zone near Cleveland
Hill to measure fault displacement.
Initial surveys on some of these arrays
were made as early as August 12, 1975,
11 days after the earthquake. Maximum
displacements measured by April 1976,
(Philip Harsh, person, commun., 1978)
were 34.1 mm (1.3 in) extensional sepa-
ration and 28.8 mm (1.1 in) vertical
displacement for the August 12, 1975,
to April 4, 1976, period, with a com-
puted dip-slip component of 44.6 mm
(1.8 in). Eight millimetres (0.3 in)
of right lateral displacemnt also were
measured. Displacement measured in
April 1976, on the other four arrays
were markedly smaller, ranging down to
a minimum of 4.3 mm (0.2 in) vertical
displacement and 0.6 mm (0.02 in) exten-
sional separation for the October 1975,
to April 1976, period.
The U. S. Geological Survey surveyed the
arrays again in February 1978. Only
dip-slip results from the 1978 survey
have been reported to DWR, but the data
does show movement continued. The
44.6 mm (1.8 in) component of dip-slip
reported in 1976, increased to 57.6 mm
(2.3 in).
An additional array of survey monuments
was installed north of the U. S. Geolo-
gical Survey array, by the Department
of Water Resources, to measure changes
in ground elevation across fault rupture
discovered in October 1975. The DWR
monuments were first releveled in
October 1975, and last measured in
October 1977. Maximum change in eleva-
tion across the fault zone by
October 1977, (See Figure 90, Chapter IV)
was 50 mm (2 in) ,with the east side of
the fault zone going up 10 mm (0.4 in),
and the west side going down 40 mm
(1.6 in).
Total fault displacement is not known,
because the increment of movement between
the time the earthquake occurred and the
time the survey monuments were installed
is not accounted for. However, compar-
ing what was seen in the field with the
survey data, gives the impression that 1
the survey data probably accounts for 1
most of the fault displacement.
The fault displacement cannot be evalu-
ated precisely and, in fact, appears
to vary from place to place. Maximum
width of cracking measured over 40 mm
(1.6 in), but this may be in part due to
crumbling away of the crack edges. Most
of the cracking was 25 mm (1 in), or less,
in width. The collective data suggests
vertical movements of about 50 mm (2 in)
and horizontal extension of about 25 mm
(1 in) . It is expected another earth-
quake of similar magnitude would pro-
duce similar displacements .
GROUND ELEVATION CHANGES
Immediately after the August 1, 1975,
earthquake. Department of Water Resources
survey teams conducted first-order lev-
eling traverses on the pre-existing
Oroville project survey network. Points
and lines were added to the network to
provide additional elevations where
needed. These lines were releveled at
approximate six-month intervals through
the next 26 months. For calculating
elevation changes, a benchmark near the
eastern edge of the project area was
considered to be stable and all other
points were adjusted accordingly.
Contours of elevation change for vari-
ous time intervals following the earth-
quake were calculated and plotted by
26
computer. These plots were overlaid on
geologic maps and analyzed for relation-
ships to geologic structure and litho-
logic distribution. The plot for the
period of August 1975, to October 1976,
is shown in Figure 14. Since the inter-
vals represented are all after August 1,
1975, the changes plotted do not include
any changes which may have occurred con-
currently with the main earthquake or
early aftershocks.
In general, the settlement contour maps
show an abrupt lowering of the ground
surface west of a north-trending zone
that coincides approximately with the
Cleveland Hill Fault. Maximum total dif-
ferential elevation change across this
zone, for the period of August 1975,
to October 1976, was 42 mm (1.7 in).
The amount of settlement decreases to
the north; survey control is lacking to
determine how far this trend continues
to the south. Elevation changes in the
northern portion of the area are of les-
ser magnitude, generally less than
25 mm (1 in) , and are not readily rela-
ted to local geologic structure.
Repeated surveys show elevation changes,
including increases, decreases and rever-
sals in direction, continuing throughout
the area — but at a decreasing rate.
The continuing elevation changes suggest
that readjustment along the fault zone
was occurring 26 months after the main
shock.
Because initial studies indicated the
northward progression of ground cracking
was trending toward Bidwell Canyon
Saddle Dam, periodic surveys were made
along the crest of the dam to monitor
changes in elevation. Results of these
surveys are shown in Figure 15. The
level line along the dam crest was sur-
veyed four times since the earthquake.
These surveys show the dam went down
about 15 mm (0.6 in) more on the west
than on the east. Most of the eleva-
tion change occurred at the west end in
the vicinity of shearing in the founda-
tion. The marked lowering of elevations
in the vicinity of Monuments BB-2 and
BB-8 are mostly due to embankment set-
tlement at places of maximum embankment
height.
Although not conclusive, these data
strongly suggest that the down-to-the-
west pattern of crustal movements seen
at Cleveland Hill continues, albeit
somewhat diminished, northward to Bidwell
Canyon Saddle Dam.
Four shears exposed in the foundation
excavation for the saddle dam are shown
on Figure 15. Most of the elevation
change appears to be in the vicinity of
the largest shear zone near the west end
of the dam. This suggests the shearing
at the west end of the dam is a zone
along which the elevation changes are
occurring. If so, the zone along which
the Cleveland Hill Fault displacements
occurred to the south, may pass through
the west end of the Bidwell Canyon
Saddle Dam.
AREA LINEAlffiNTS
A photo lineament is defined as, "Any
line, on an aerial photograph, that is
structurally controlled, including any
alignment of separate photographic images
such as stream beds, trees, or bushes
that are so controlled. The term is
widely applied to lines representing
beds, lithologic horizons, mineral band-
ings, veins, faults, joints, unconformi-
ties, and rock boundaries" (Allum, 1966,
p. 31). Because lineaments are often
fault related, they are useful indicators
of possible faults. Consequently, one
of the early tasks for this project was
to plot regional lineaments on topogra-
phic maps and then inspect them in the
field.
The study of area lineaments began in
May 1976, with a field reconnaissance of
major photo lineaments north of Oroville
Reservoir. A more comprehensive study,
including detailed mapping and field
observations, was done in September and
October 1977. A similar study was con-
ducted in 1976-77 by the U. S. Army
Corps of Engineers as a part of their
27
3 KILOMETRES
CONTOUR INTERVAL • 9 MILLIMETRES
Figure \k. Changes in ground elevations around Lake Oroville, August 1975, to
October 1976
28
29
Marysville Lake project. Their work
covered an area from Oroville to 9.6 km
(6 mi) south of the Yuba River (U. S.
Army Corps of Engineers, 1977).
Woodward-Clyde Consultants also per-
formed a major study of lineaments in
the foothill belt as part of a seismic
investigation for the Auburn Dam
project.
The purpose of the lineament study was
to determine which lineaments are faults.
Methods of investigation included aerial
reconnaissance, photo interpretation,
field inspection and mapping; topography,
springs, continuity of rock units, fault
gouge or any other features which would
suggest or refute faulting were investi-
gated. Previous geologic maps were
field checked and incorporated in the
study.
Lineaments are categorized according to
degree of certainty for a fault origin.
Three categories are identified:
(1) lineaments where field evidence con-
tradicts a fault control and suggests
origins are due to other causes (indi-
cated as photo lineaments, dotted lines
in Figure 16); (2) lineaments with no
direct evidence of faulting, but are
still thought to be faults (probable
fault, dashed lines in Figure 16); and
(3) lineaments which are faults (solid
lines in Figure 16) .
Three major photo lineaments are within
the study area. These include the
Paynes Peak, Swain Ravine and Prairie
Creek Lineaments. Surface and subsur-
face data have been analyzed by
California Department of Water Resources,
Woodward-Clyde Consultants, Pacific Gas
and Electric Company, U. S. Army Corps
of Engineers, U. S. Bureau of Reclamation
and U. S. Geological Survey in attempts
to evaluate the past history of activity
along these fault zones.
The major fault lineaments are in places
defined by broad discontinuous linear
valleys and aligned sections of sheared
rock. The lineaments are not continuous
but have gaps where nothing is evident
either on imagery or on the ground. The
Cleveland Hill faulting started in one
of these lineament gaps. The Swain
Ravine Lineament merges with the Prairie
Creek Lineament approximately 10 km
(6 mi) north of the Bear River. In turn,
the Prairie Creek Lineament extends
southward and is truncated west of
Auburn by the Rocklin pluton.
GEOLOGIC SETTING
Geographic Location
The Oroville study area is within the
Sierra Nevada of California (Figure 17).
The foothills of the Sierra Nevada sepa-
rate the Sierran uplands from the rela-
tively flat Sacramento and San Joaquin
Valleys (the Great Valley) . The study
area comprises the northernmost part of
these foothills.
Immediately north of, and included in
the reconnaissance study, is the southern-
most portion of the Cascade Range.
Across the northern end of the Great
Valley, northwest of the study area, are
the Klamath Mountains which share many
structural and lithologic characteris-
tics with the Sierran foothills.
Geologic Framework
The Sierra Nevada province is an up-
lifted block of Mesozoic plutonic and
metamorphic rock bounded by normal
faults on the east and tilted to the
west. The eastern side is very steep
with pronounced fault topography, while
the western side is of gentler relief.
The regional geologic fabric of Northern
California is oriented north-northwest.
Generally following this fabric is the
Sierra Nevada crest, boundary faults,
rock fabric, and foothills faults. The
axis of the Great Valley, the crest of
the Coast Ranges, and major faults in
the Coast Ranges (e.g., San Andreas)
also conform to this regional trend.
The foothills of the Sierra Nevada are
underlain by Paleozoic to Mesozoic
30
SCALE OF MILES
SCALE OF KILOMETRES
YubO City^
Fiqure 16. Lineaments and faults in the northwestern Sierran foothills
31
;
I
\ KLAMATH \ \ MODOC '^ ^
> MOUNTAINS , \ PLATEAU i '
; ' ^
\ /
\ ^' (
/ CASCADE' \
V RANGE
CHEROKEE ''
-^ BERRY
CREEK
OROVILLE
OROVILLE
DAM
PALERMO
BANGOR
39° 22 30
Quadrangles comprising the
geologic nnap.
DESERT
^ .o-\
O,
-C<
<>\
l'/^/ ^ o.^
^ej-^!.
S ^'9
Figure 17. Natural geologic provinces of California with field area location
32
metamorphosed sedimentary and volcanic
rocks, and plutons which are similar to,
but generally smaller than, those form-
ing the Sierra Nevada. The metamorphic
fabric and trend of faults in the foot-
hills are most commonly concordant with
regional northwest trends; local varia-
tions occur about the intrusive bodies.
Overlying the metamorphic foothills
bedrock is a thick sequence of unmeta-
morphosed upper Mesozoic and Cenozoic
sedimentary and volcanic rocks (Super-
jacent Series rocks) and alluvium.
These rocks are in most places undeform-
ed and dip gently west.
The northern foothills have recently
been interpreted as remnants of Mesozoic
subduction complexes consisting of me-
lange, arc rocks and ophiolite (Moores,
1972; Cady, 1975; Schweickert and Cowan,
1975; Buer, 1977, 1978; this study);
this model also has been applied to the
Klamath Mountains and Coast Ranges
(Davis, 1969; Hamilton, 1969). The sub-
duction zone is thought to have migrated
westward during Late Jurassic time to
form melanges of the Coast Ranges
(Hamilton and Myers, 1966; Hamilton,
1969; Burchfiel and Davis, 1972, 1975).
DESCRIPTIVE GEOLOGY
Bedrock Series Rocks
Global applications of sea-floor spread-
ing, as proposed by Hess (1959, 1962),
have conceived new explanations and
evolutionary interpretations for sea
floor and continental rocks. Bedrock
suites in this investigation are mapped
and described assuming plate tectonic
modes of origin and using evolutionary
names, rather than formational names.
Previous formational names are referen-
ced in describing lithologic groupings.
Geologic mapping of individual rock
suites established the present structu-
ral configuration and provides explana-
tions for plate tectonic development of
the region; this includes the origin of
lithologic suites and time-separated
episodes of faulting. Lithologic suites
in the area include:
(1) Melange - This suite consists of
chaotically mixed metasedimentary and
metavolcanic rocks which include serpen-
tine and exotic blocks of marble. Me-
lange was formed at a convergent bound-
ary that existed between late Mesozoic
California (American plate) and Pacific
sea floor (ancestral Farallon plate that
is now subducted beneath American plate) .
These rocks formed by subduction under-
thrusting as an accretionary prism in
the Benioff zone.
(2) Arc rocks - Rocks in this suite
are volcanic and volcaniclastic deriva-
tives that formed as an island arc com-
plex in the ocean adjacent to Mesozoic
California. Island arcs, common in many
of todays oceans, develop relatively
close to convergent plate boundaries
where subducted lithosphere melts as it
descends into the earth. The melted
rock rises because of a lighter specific
gravity, and volcanic mountains form if
magmas reach the surface.
(3) Ophiolite - This lithologic suite
is named Smartville ophiolite in the
study area and includes metamorphosed
mafic rocks (amphibolite) that have ori-
gins peculiar to the sea floor. Ophioli-
tic suites form at oceanic spreading
centers (rifts) and require that several
mafic and ultramafic rock types be pre-
sent for a complete ophiolite sequence.
These lithologies form layers of varying
thickness in undisturbed ophiolite and
include: (1) an overlying mantle (layer
1) of marine sediment and chert; (2) an
intrusive-extrusive complex (layer 2) of
submarine-extruded pillow lava that was
fed by, and grades downward into intru-
sive sheeted dikes; (3) a quasi-
stratiform intrusive complex (layer 3)
of gabbro, cumulate gabbro and dunite;
and (4) a tectonite basement (layer 4)
consisting of harzburgite and minor
dunite. Ophiolite exposed within con-
tinental margins necessitates special
processes (obduction) for emplacement
from oceanic source areas.
33
Melange
Previous Investigations and Age;
Melange rocks in the western Sierra
Nevada were first mapped and named
"Calaveras formation" by Turner (1893,
p. 309) for prominent exposures in
Calaveras County. The name "Calaveras
formation" subsequently became a
"...catchall for all Paleozoic rocks in
the Sierra Nevada and hence has no
stratigraphic significance. ..."
(Taliaferro, 1943, p. 280); this excludes
Silurian and Upper Carboniferous rocks
in the Taylorsville region. Exposures
of Calaveras rock have been studied in
many investigations (Lindgren, 1900;
Clark, 1964, 1976; Creely, 1965;
Hietanen, 1973a, 1976, 1977), but no
regional correlation of units has been
achieved.
The first detailed study of melange in
the immediate area was by Creely (1965).
He subdivided and described the Pentz
Sandstone and Hodapp Members from the
Calaveras Formation; however, most occur-
rences of the formation were mapped as
"undifferentiated Calaveras".
Melange terrane northeast of the study
area is subdivided by Hietanen (1973a)
into the Calaveras, Horseshoe Bend,
Duffey Dome and Franklin Canyon Forma-
tions. In later works, Hietanen (1976,
1977) further mapped, subdivided and
described the Horseshoe Bend Formation
(Berry Creek quadrangle) and noted that
these rocks are physically continuous
with Creely 's Calaveras Formation to the
east. In Hietanen' s works no mention of
melange was used to describe these com-
plex rock suites.
The first published description of
melange in the Sierran foothills was by
Moores (1972), who suggested that "rem-
nants of subduction zones" may be present
in foothill areas. Subsequent studies
(Bateman and Clark, 1974; Duf field and
Sharp, 1975; Schweickert and Wright,
1975; Schweickert and Cowan, 1975) have
noted the widespread presence of melange
in the Sierran foothills. Most recent
studies, recognizing the nature of these
suites, have dropped the name "Calaveras
Formation" and adopted the term "melange"
to describe the rocks.
The age of melange in the foothill belt
is misinterpreted as being late
Paleozoic by most earlier researchers
(Turner, 1893, 1894, 1896; Lindgren,
1900; Taliaferro, 1943, 1951; Clark,
1964, 1976). Early ages were establish-
ed by using Tethyan fossils (Douglas,
1967) in limestone and marble bodies
that crop out in melange matrix. These
carbonate bodies are interpreted to be
exotic blocks within melange.
Fossils collected from exotic blocks in
melange do not represent the age of
melange formation, but rather the age of
the exotic block. In the Klamath Mount-
ains late Paleozoic fossils are in bodies
of limestone and marble (Irwin, 1972;
Irwin and Galanis, 1976); cherts in
melange-type rocks that include these
carbonate bodies yield Late Jurassic
radiolarians indicating the rock suites
are much younger than fossils in marble
and limestone bodies suggest (Irwin and
others, 1977) .
An Upper Jurassic fossil (a pelecypod,
Buchia Concentrica as identified by, and
in possession of Ralph Imlay, U. S. Geo-
logical Survey) was discovered in meta-
sedimentary melange near Pentz, Califor-
nia (Bob Treet, person, commun., 1978);
the fossil specifically dates from middle
Oxfordian to upper Kimmeridgian time.
The Buchia fossil locality is in the
southeast quarter of section 13 (T21N,
R3E) on the Cherokee qixadrangle. It
substantiates that melange (Calaveras
Formation) in the northwestern Sierran
foothills is much younger than previously
suggested. The Upper Jurassic age of me-
lange is the same as arc and ophiolitic
rocks located to the south and indicates
contemporaneous origins.
Contact Relationships; The southern
margin of melange in the project area
34
is interpreted to be an obduction bound-
ary with arc rocks in the Cherokee quad-
rangle. The contact with arc and ophio-
lite in the Berry Creek quadrangle is
complex and not well exposed. The base
of melange is not exposed in the study
area.
Melange in the study area is overthrust
by obducted arc rocks. Allochthonous
rocks underlie large portions of the
northern study area and form more sur-
face exposure than autochthonous me-
lange. Uncertainty exists as to how
much melange is overridden.
Lithologic Description; The melange
complex in the study area includes meta-
sedimentary rocks (argillites, schists,
phyllites, meta-tuf faceous beds, relict
pebble conglomerates, exotic marble
blocks and chert), metavolcanic rocks
(relict basalts, diabases and andesites)
and serpentine. These rocks, mixed by
tectonic and olistostromal processes,
are isoclinally deformed into tight
folds that dip vertically or steeply to
the east (Figure 18) . Structural dis-
continuity and intercalation of melange
lithologies suggests the sequence origi-
nated as an accretionary prism in a sub-
duction zone; similar rocks and structu-
ral relationships are described at many
active and ancient subduction zones
(Hsu, 1971; Blake and Jones, 1974;
Gansser, 1974; Karig, 1974; Scholl and
Marlow, 1974; Karig and Sharman, 1975;
Dickinson, 1975). Accretion, using sev-
eral different models (Burk, 1965; Dewey
and Bird, 1970; Gilluly, 1972; von Huene,
1972; Moore, 1973), is postulated as the
process by which lower plate rocks be-
come transferred (accreted) to the upper
plate during subduction.
Relict basalt, diabase and andesite
flows (?) and sills (?) are the most
abundant metavolcanic rocks incorporated
in melange. They are locally intercal-
ated within metasedimentary sequences.
Contacts between metavolcanic rocks and
metasedimentary rocks are poorly exposed.
Figure 18. Small-scale parasitic isocl inal Figure 19. Relict bedding (parallel to
fold within melange metasedimentary rock, pencil) cross cut by steeply east-dipping
1.5 km (1 ml) southwest of the West foliation in melange metasedimentary rock,
Branch Bridge. 1.5 km (1 mi) southwest of the West
Branch Bridge.
35
Meta-basalts and -diabases include ura-
litized amphibole and/or pyroxene,
sodic plagioclase and secondary epidote.
Accessory minerals are ilmenite or hema-
tite, quartz and secondary chlorite.
Argillites and metagraywack.es are dark
when fresh and retain some of the ori-
ginal sedimentary features; shearing
has locally transposed depositional
structures into the plane of foliation
(Figure 19). Sodic plagioclase, quartz,
epidote, muscovite, chlorite and traces
of metallic minerals comprise argil-
laceous rocks.
Pebble metaconglomerates of volcani-
clastic origin are locally common within
melange matrix (Figure 20). These are
in places exposed against deep-water
slates. Shearing has stretched clasts,
however, the volcanic origin of both
clasts and matrix remains visible.
Schistose and phyllitic rocks vary from
dark- to light-green where fresh and
Figure 20. Sheared volcaniclastic meta-
conglomerate intercalated with black
slates (not shown) in melange meta-
sedlmentary rock. Location is 1.5 km
(Imi) southwest of the West Branch
Bridge.
are various shades of buff if weathered.
Syntectonic shearing has destroyed ori-
ginal textures.
Chert has limited exposure in melange
terrane. Localized occurrences expose
thin- to medium-bedded light-gray to
white chert. Thin sections indicate
chert is composed of 95 to 100 percent
recrystallized quartz. Most chert in
melange was clastically derived
(Hietanen, 1977, p. 7).
Marble in melange (Figure 21) is
white to bluish-gray. Most occurrences
of marble are exotic and do not repre- d
sent original in situ deposition. Sam- j
pies collected along Nelson Bar Road |
(Cherokee quadrangle) exhibit marble ,
and phyllite incorporated to form a rock
with foliation discordantly cross-cutting
the contact between the two lithologies
(Figure 22). This indicates marble was
incorporated into fine-grained sediments
prior to metamorphism. An absence of
shear at the marble-phyllite contact
MARBLE
Figure 21. View north from the West
Branch Bridge of exotic marble block
in melange.
36
igure 22. Sample of ol i stostromal marble-phy
Bar Road just east of Oroville Reservoir (Ch
and phyllite is nearly perpendicular to the
types.
suggests gravity was the emplacement
mechanism; therefore,' this deposit is
an olistostrome. Olistostromal deposits
and tectonic knockers are common in many
melange deposits (Hsu, 1965, 1968;
Raymond, 1977).
The distribution of fossilif erous
marble in the field area is restricted
to a linear belt of exposures in West
Branch Canyon. Marble exposures in other
areas are scarce, non-fossiliferous and
concordant with local bedding in meta-
sedimentary melange.
Light- to dark-green serpentine, as
highly-sheared to unsheared rocks, forms
elongate discontinous exposures that are
concordant with the local foliation.
1 1 i te collected in melange along Nelson
erokee quadrangle). Foliation in marble
unsheared contact between the two rock
Contacts between serpentine and adja-
cent rocks are poorly exposed. Plate
tectonic models associate serpentine
with subduction (Benioff) zones at con-
vergent boundaries (Hamilton, 1969;
Bailey and others, 1970; Bateman and
Clark, 1974; Lapham and McKague, 1964;
Coleman, 1977). Lockwood (1971, 1972)
has suggested that serpentine can be
clastic or deposited as olistostromes.
However, the sheared and truncated na-
ture of serpentine in the study area
suggests it was tectonically emplaced
as opposed to a depositional origin.
Elongate serpentine exposures in the
area are interpreted as locations of
ancient shear zones within the subduc-
tion complex.
37
Metavolcanic arc rocks are exposed in
melange in the Cherokee and Berry Creek
quadrangles. Contacts are not well ex-
posed but most appear to be relatively
flat-lying; these contacts conform to a
model of arc rock overthrust on melange.
It is possible that arc rocks were tec-
tonically mixed into melange during sub-
duction, however, it is also possible
that the thrust plane has been folded
and these exposures of arc rock are
klippen.
Arc Rocks
Previous Investigations and Age; Base-
ment Series greenstones in the Sierran
foothill belt were first mapped and des-
cribed by Becker and others (1898), and
Lindgien and Turner (1895). Greenstone
descriptions from these studies are re-
fined in several later works (Creely,
1955, 1965; Bateman and Clark, 1974;
Clark, 1976; Hietanen, 1977). Moores
(1972) suggests part of the greenstone
complex is an ancestral island arc.
Subsequent investigations (Cady, 1975;
Moores, 1975; Schweickert and Cowan,
1975; this study) have subdivided Sierran
foothill greenstones into members whose
origins are explained using a plate tec-
tonic framework.
The most detailed academic study involv-
ing the westernmost suite of volcanic
and volcaniclastic rocks in the green-
stone belt is by Creely (1955, 1965).
He applied the name "Oregon City Forma-
tion" to describe this metavolcanic se-
quence that is now recognized as an arc
complex. These rocks are dated Late
Jurassic (Oxfordian to Kimmeridgian) by
an ammonite identified as Perisphinctes
by Professor S. W. Muller, Stanford
University (Creely, 1965).
Contact Relationships: A reverse fault
forms the eastern contact of arc rocks
with Smartville ophiolite in the Oroville
area. Western margins of the arc com-
plex are unconformably overlain by late
Cenozoic Superjacent Series deposits
and alluvium. Arc rocks are not exposed
in contact with other Basement Series
rocks west of the foothills.
The arc complex ends abruptly in the
southeastern Cherokee quadrangle. Field
evidence at this location indicates arc
rocks are thrust over melange by a late
Mesozoic thrust fault. This fault is
nearly flat-lying and probably represents
an obduction suture.
Arc lithologies in the Oroville area
are physically continuous to the south
with Browns Valley Ridge volcanic rocks
located in the foothills east of
Marysville. Further south, they are
time and structurally correlative with
the Copper Hill and Gopher Ridge volcanic
sequences located north of the Mokelumne
River (Duffield and Sharp, 1975).
The base of the arc complex is not ex-
posed in the study area. The thickest I
sequence is exposed in Morris Ravine on
the west limb of the Monte de Oro syn-
cline and includes approximately 400 m
(1315 ft) of section.
Lithologic Description; Exposures of
fresh arc rock are dark- to light-green
and extremely well indurated. Foliation
and relict flow structure are poorly
developed.
Foliation is generally accentuated by
weathering. It is not known if folia-
tion and relict flow structure are con-
cordant; metamorphism has transposed
original structures in local metasedi-
mentary rocks (Figure 23), and this
characteristic probably exemplifies
foliation in the arc sequence.
The arc complex is formed by several
fine- to coarse-grained lithologies that
are intermediate to basic in composition.
Arc lithologies include andesitic tuff-
breccia, lapilli tuff agglomerate, and
epiclastic derivatives of these rocks;
tuff-breccia and monolithologic agglome-
rates (Figure 24) are by far the most
common. Relict flows, pillows (Figure
25), and sills (?) of meta-andesite
and -basalt are present but not common.
38
Figure 23. Arc metased imentary rock
displaying relict bedding (dipping
into photograph) that is nearly per-
pendicular to steeply east-dipping
foliation (subparallel to pencil).
Figure 2A. Arc complex metavolcanic
tuff breccia at The High Rocks,
approximately 1 km (0.6 mi) south-
east of Oregon City. Note pocket
knife for scale.
Figure 25
4 km (2
Note pen
Pii-UDW
I
X'
Arc complex relict pillow and flow lavas cut by fault,
5 mi) northeast of Oregon City along the North Fork of
cil (center-left) for scale.
approximately
Lake Orovi 1 le.
39
The fine-grained, metamorphosed nature
of arc rocks makes field identification
difficult; however, most of the present
complex was probably water-lain.
Tuffaceous rocks include hornblende
and/or augite, sodic plagioclase (saus-
suritized) and lithic fragments; these
are set in a finer-grained tuff matrix
which comprises the bulk of the forma-
tion. Vesiculated lithic fragments are
commonly angular and of one rock type,
suggesting derivation from local erup-
tive vents. Subrounded fragments of
different rock types also are common
and represent clastic water-lain se-
quences (Figure 26). Vesicles in clasts
vary from 2 to 8 mm (0.08 to 0.3 in) in
diameter and are filled with secondary
quartz. Common minerals include epidote,
clinozoisite, chlorite, and pyrite.
Much of the groundmass observed in
thin section is cryptocrystalline and
comprises unidentifiable alteration pro-
ducts derived from secondary and meta-
morphic mineral reactions.
Monte de Oro Formation
Previous Investigations and Age: The
Monte de Oro Formation was named and
first described by Turner (1896) . His
work noted fossil debris throughout the
formation which probably inspired some
of the later studies. Subsequent inves-
tigations (Fontaine, 1900; Knowlton,
1910; Diller, 1908; Taliaferro, 1942;
Creely, 1965) describe these rocks in
great detail. Fossil flora, and to a
lesser extent fauna, provided the earli-
est evidence that rocks in the Oroville
area have Jurassic ages.
Contact Relationships; Monte de Oro
Formation in the study area represents
the tightly folded axis of a syncline
overturned to the west. Approximately
375 m (1,230 ft) of Monte de Oro Forma-
tion is stratigraphically exposed.
Figure 26. Relict bedding and cross-bedding in arc tuff breccia and tuffaceous
metasedimentary rock, 5 km (3 mi) southeast of Palermo. Darker area of outcrop
(right-center) was wetted to accentuate structure.
40
The western contact of Monte de Ore
Formation is depositionally conformable
on arc rocks. Arc complex flows are
intercalated with bedding in lower por-
tions of Monte de Oro Formation and
form a gradational contact between the
two sequences; for this reason, Monte de
Oro rocks are interpreted to be a sedi-
mentary facies of the arc complex. The
eastern margin of the formation is trun-
cated against arc rocks by an east-
dipping reverse fault.
Lithologic Description; Monte de Oro
Formation in the Oroville area represents
the only named exposures of these rocks
in the Sierran foothills; however, simi-
lar metasedimentary rocks are exposed
in the Bangor quadrangle to the south.
These rocks are in structural alignment
with Monte de Oro rocks near Oroville
and may have been deposited in a common
Upper Jurassic environment.
The Monte de Oro Formation is predomi-
nantly slightly-sheared, well-indurated,
dark sandstone, siltstone, conglomerate
and poorly-developed slate. Argillaceous
siltstone and sandstone (metagrajwacke)
with poorly-developed interbedded slate
constitute the bulk of the formation.
Exposures of metasiltstone are dark- to
olive-gray where fresh and weather to
light-olive-buff. Metasiltstone, com-
monly containing relict sandy and clayey
sections, is moderately- to well-bedded
and laterally continuous. Plant debris
is locally abundant on metasiltstone
bedding-plane cleavages.
Monte de Oro metasandstone is poorly-
bedded and includes graywacke and arkose.
Relict sandstone beds have lenticular
shapes and are laterally discontinuous.
The bulk of this material occurs in
lower portions of the formation and is
believed to have been reworked from
underlying arc rocks.
Graywacke consists of subrounded,
medium- to coarse-grained, poorly-sorted,
feldspar, rock fragments and quartz or
detrital chert. These constituents are
cemented by clay and silica (?) in an
argillaceous matrix.
Arkose is fine-grained and consists
predominantly of subrounded, moderately-
to well-sorted feldspar. Clastic grains
are set in a green chlorite (?) relict-
silt matrix.
Monte de Oro metaconglomerate is formed
of subangular to rounded, pebble- to
cobble-sized clasts set in an argil-
laceous relict-sandstone matrix. These
beds are lenticular and most abundant in
relict sandstone sequences.
Predominant clast types in metacon-
glomerate are poorly sorted and include
plagioclase- and quartz-rich porphyritic
dacite (?), dark chert and black slate.
Dark, fine-grained, indeterminate volcanic
clasts are common but less abundant.
It is significant that many of the
clasts in Monte de Oro metaconglomerate
are not derived from the underlying arc
complex. Exotic volcanic clasts, as
well as accompanying chert and slate,
were probably derived from pre-arc ter-
rane; these sources may include melange.
Smartville Ophiolite
Previous Investigations and Age:
Studies by Lindgren and Turner (1895)
and Becker and others (1898) provide
early maps and descriptions of meta-
volcanic greenstones in the northwestern
Sierran foothills. The first detailed
investigations of this greenstone suite
were by Hietanen (1951), Compton (1955)
and Creely (1955, 1965). More recent
investigations (Moores, 1972, 1975;
Cady, 1975; Schweickert and Cowan, 1975;
Bond and others, 1977; Buer, 1977;
Day, 1977; Hietanen, 1977) describe this
greenstone sequence as dismembered
ophiolite.
Cady (1975) proposed the name Smartville
ophiolite in his study. This name is
adopted in our investigation.
The age of Smartville ophiolite was
Al
originally suggested to be late Paleozoic
by Creely (1965) from a comparison with
Oregon City Formation (arc complex) that
was dated by fossils. In later works,
Cady (1975) and Hietanen (1977) consider
these rocks to be Jurassic in age.
The Smartville complex is interpreted
to have formed by back-arc spreading
(Schweickert and Cowan, 1975; Eldridge
Moores, person, commun., 1977); similar
spreading basins are active today in
many areas of the Pacific Ocean
(Hamilton, 1969; Karig, 1970, 1971a,
1971b, 1972; Moberly, 1972; Churkin,
1975; Karig and Sharman, 1975). Behind-
the-arc spreading is suggested to have
occurred in Callovian to Oxfordian time
by Schweickert and Cowan (1975); however,
their model has ophiolite originating
prior to eruption of the Oxfordian age
(Creely, 1965) Oregon City volcanic se-
quence. Smartville ophiolite is now
interpreted to have formed in late
Oxfordian to early Kimmeridgian time
which is younger, but in part coeval with
development of the arc complex.
A fault separates arc rocks and ophi-
olite in the study area, therefore, di-
rect evidence is lacking to substantiate
whether arc rocks are intruded by source
magmas from a spreading interarc basin,
or if the arc complex is built upon
ophiolite. Field evidence is inconclus-
ive and consists of: (1) Arc litholo-
gies on Bloomer Hill, in the Berry Creek
quadrangle, overlie ophiolite; however,
poor contact exposures prevent a deter-
mination of whether the contact is depo-
sitional or fault controlled. (2) In
the foothills east of Marysville, meta-
basaltic dikes similar to those in
ophiolite appear to intrude arc litholo-
gies of the Browns Valley Ridge volcanic
sequence (Costas Xenophontos, person,
commun., 1978). (3) A few hundred metres
west of the California Highway 20 bridge
over the Yuba River, Smartville pillow
basalt is conformably overlain by argil-
lite and arc-derived (Koll Buer, person,
commun., 1978) tuff and pyroxene ande-
site tuff breccia.
Contact Relationships; The western
margin of Smartville ophiolite in the
study area is a near-vertical fault.
The fault is not regional in extent; arc
and ophiolite sequences are conformable
along the Yuba River south of the area.
Sierran plutons truncate Smartville
ophiolite on the east. Intrusive rocks
entered ophiolite in directions subparal-
lel to regional foliation.
The northern margin of the Smartville
belt is poorly exposed; abundant meta-
volcanic rock in melange further inhibits
locating and interpreting the nature of
the ophiolite-melange contact. The con-
tact, although not mapped, is interpre-
ted to be an obduction boundary.
Lithologic Description; Smartville
terrane is a dismembered complex and
does not contain all of the rock types
and structural levels characteristic of
ophiolite sequences as described by sev-
eral researchers (Moores and Vine, 1971;
Moores and Jackson, 1974; Coleman and
Irwin, 1974; Williams and Stevens, 1974;
Coleman, 1977). Common lithologies and
structural layers that characterize the
Smartville complex (Figure 27) include;
(1) metasedimentary rock of layer 1
ophiolite; (2) layer 2 meta-basaltic
and -diabasic pillows, pillow breccia,
dikes and sills over a complex of meta-
basaltic and -diabasic dikes and sheeted
dikes with felsic and gabbroic screen
rocks; and (3) upper layer 3 gabbroic
intrusions. Layer 2 pillows, dikes and
sheeted dikes, with or without screen
rocks, are the most common ophiolite
members in the area. Layer 3 gabbroic
intrusions, common in many ophiolites
(Cass and Smewing, 1973; Jackson and
others, 1975; Tysdal and others, 1977),
are scarce in Smartville terrane.
Individual pillows (Figure 28) have sub-
spheroidal to lobate shapes and are
usually poorly preserved. Well-
developed pillows of the Smartville com-
plex are exposed south of the project
area along the Yuba River (Figure 29).
42
OPHIOLITE STRATIGRAPHY
STANDARD OCEANIC CRUST SMARTVILLE OPHIOLITE
SEDIMENTS
PILLOW BASALTS
LAYER 2 i[,2 MASSIVE BASALT AND
>° DIABASE SHEETED
5J DIKES AND SILLS
LAYER 3^0.
CUMULATE GA8BR0
CUMULATE PYROXENITE
CUMULATE DUNITE
LAYER 4 tz HARZBURGITE WITH
§2 MINOR DUNITE
?FLYSCH + TUFF t CHERT
^PILLOWS + FLOWS +
SILLS 1 BRECCIA
SHEETED DIKES
MAFIC DIKES
FELSIC AND GABBROIC
SCREENS
DIKE-GABBRO TRANS-
ITION SOME PLAGIO-
GRANITE AND DIORITE
Figure 27- igneous stroligropny of Stondord Oceanic Crust with member thicknesses (after Moores
and Jockson, 1974) ond Smortville ophiolite. Note that sections shown are unmetamorphosed.
In most ophiolites, pillow basalts ond the sheeted dike complex are metamorphosed to greenschist
or omphibolite facies with olmost total serpentinization of the cumulate and tectonized
ultromofic rocks. An extensive shear zone commonly seporotes the cumulate and tectonized
ultramofic rocks
Figure 28. Well -developed metavolcanic
Smartville pillows 1.5 km (1 mi) south
west of Bangor.
Synkinematically sheared pillows com-
monly yield phyllonitic rock (Figure 30)
In shear zones all original rock struc-
ture is transposed and forms a cata-
clastic foliation.
Metabasalt forms most pillows and is
dark-green to gray-green when fresh.
Pyroxene, albite, epidote, and pyrite
are the only minerals identifiable in
hand specimen. Relict vesicles, filled
with secondary quartz and epidote, are
in places abundant. Quartz and epidote
also fill discontinous veinlets in these
rocks and the cores of some pillows.
Sparse hyaloclastite or aquagene tuff
forms selvages aroimd individual pillows.
Chert has been described as abundant in
some pillow basalts (Bailey and others,
1964) but is not common in Smartville
rocks.
43
-,J.
.^
:/
/
J. ^
Figur
of
ind
and
e 29.
the Ca
i vidua
di ps
Well developed metavolcanic Smartville pillows at the south abutment
lifornia Highway 20 bridge crossing of the Yuba River. Tails on
I pillows indicate the section is right-side-up (to top of photograph)
steeply west.
Pillowed basalt grades downward into
meta-diabasic and -basaltic dikes and
sheeted dikes (Figure 31) . Dikes com-
prise the greatest volumne of Smartville
ophiolite in the study area. Models
describing ophiolite (Moores and Vine,
1971; Moores and Jackson, 1974) identify
lower layer 1 as a structural level where
meta-basaltic and -diabasic dikes and/or
sills intrude pillows. This relationship
is rare in the project area.
Gabbroic and felsic screen rocks, indi-
cating a deeper level of the ophiolite
complex (Moores and Vine, 1971; Moores
and Jackson, 1974), are locally abundant
(Figures 32 and 33). Felsic screen rocks
include quartz diorite, granophyric kera-
tophre and trondhjemite, and represent
differentiates from late-stage crystal-
lization of sub-akaline magmas (Coleman,
1971, 1977). Hyaloclastite screens are
enclosed in dikes along California
Highway 162 just south of Canyon Creek
Bridge. These screens are phyllitic.
Figure 30. Sheared metavolcanic Smart-
ville pillows in North Honcut Creek
stream bed near bridge crossing of
the Oro-Bangor Highway. Shearing
renders the outcrop appearance of a
phyllonite. Note pencil (center-
right) for scale.
44
1 A >* i
Figure 31. Steeply east-dipping metavol can ic Smartville sheeted dikes along Rocky
Honcut Creek, approximately 1 km (0.6 mi) west of Oro-Bangor Highway bridge
crossing.
Figure 32. Grabbroic screen rock in Smartville metavolcanic sheeted dikes along
Olive Highway just east of Quincy Place (Oroville quadrangle).
45
Figure 33. Granophyric screen rock i
along Rocky Honcut Creek, approxima
Highway bridge crossing,
fine- to medium-grained and contrast
greatly with the darker meta-diabasic
dikes. Tuffaceous screens indicate dikes
intruded to very shallow levels of the
ophiolite, and probably fed pillows on
the ancestral sea floor.
Dikes and sheeted dikes vary from 30 to
100 cm (12 to 39 in) in thickness and
have continuous trends where exposed;
discontinuous dikes do occur, but are
rare. Foliation is concordant with con-
tact margins. Average strikes are
N5-25W and inclinations dip steeply east
at angles greater than 65 degrees; west
dips occur locally but are not consid-
ered representative for the dike complex.
Contacts between sheeted dikes and be-
tween dikes and screens are sharp and in
places have chilled margins.
Major minerals in metavolcanic ophio-
lite are granoblastic clinopyroxene,
albite, chlorite, epidote, clinozoisite,
actinolite, tremolite and opaques (py-
n Smartville metavolcanic sheeted dikes
tely 1 km (0.6 mi) west of Oro-Bangor
rite and chalcopyrite) . Unidentifiable
cryptocrystalline metamorphic and hydro-
thermal alteration products form a
groundmass for these minerals.
Gabbroic Smartville ophiolite in the
study area is exposed as local dikes,
plugs and stocks; gabbro is regionally
limited in the complex. A gabbroic
stock, with extremely complex intrusive
contacts, is exposed west and northwest
of Stringtown Mountain, in Woodman
Ravine.
Gabbroic rock in Woodman Ravine is com-
posed of coarse-grained plagioclase and
cummulate pyroxene (uralitized) . Dikes
with well-developed chill margins cut
gabbro in this area. Dikes contain gab-
broic xenoliths which become less abun-
dant to the south. Relationships of
these mafic rocks are further compli-
cated by intrusion of the Swedes Flat
pluton.
46
Another gabbro (norite) intrusion under-
lies a small portion of the North Fork
Feather River canyon west-southwest of
Bloomer Hill. Lake Oroville inundates
much of the gabbroic surface area.
Intrusive Rocks
Previous Investigations and Age:
Several previous investigators have
mapped Sierran plutons in the study area
(Becker and others, 1898; Hietanen, 1951,
1973b, 1976, 1977; Compton, 1955;
Evernden and Kistler, 1970; Bateman and
Clark, 1974; Clark, 1976). Plutonic
terrane mapped for this project includes
only western margins of these earlier
regional studies.
Absolute ages of intrusive rocks in the
study area are established by potassium-
argon dating. Analyzed samples yield
discordant hornblende and biotite ages
and indicate that the dated plutons
have experienced post-intrusive reheat-
ing with subsequent degassing of argon.
The Bald Rock pluton yields discordant
ages of 131 and 126 million years on
hornblende and biotite respectively
(Evernden and Kistler, 1970). Two dis-
cordant age dates for the Merrimac plu-
ton, using the same minerals respec-
tively, are 129 and 131 million years
(Gromme and others, 1967) and 132 and
129 million years (Evernden and Kistler,
1970). Dated locations of these plutons
are not within project boundaries; how-
ever, granitic rocks are physically con-
tinuous from these locations into the
study area.
Ages for the Bald Rock and Merrimac
plutons indicate that emplacements were
during Jura-Cretaceous time and syn-
chronous with late stages of the Yoseraite
intrusive epoch (Figure 34) . Late
Jurassic to Early Cretaceous ages for
the Sierra Nevada intrusive complex are
suggested by several earlier researchers
(Knoph, 1918, 1929; Erwin, 1934; Mayo,
1934, 1935) without the aid of radio-
metric dating.
Contact Relationships: The Bald Rock
and Swedes Flat plutons intrude
Smartville ophiolite along the east-
central and southeast margin of the meta-
morphic complex. In most places the
plutons entered ophiolite subparallel to
the pre-existing regional foliation.
Xenoliths, from a few centimetres to
several tens of metres in diameter, are
in places locally abundant in plutonic
Age
(my.)
Sys-
tern
Se-
ries
Intrusive epoch
70-
80-
90-
100-
110-
120-
130-
140-
150-
160-
170-
180-
190-
200-
210-
220-
230-
r>
o
LJ
O
<
1-
cc
u
o.
a.
3
Cothedrol Ronge
5
o
Huntington Lake
<_)
(/)
V)
<
en
3
Q.
Cl
r)
■o
?
-J
Yosem ite
Inyo Mountains
o
V)
to
<
IT
1-
Q.
Q.
r>
-iHi-
O
_l
Lee Vining
(after Horland am' others, 1964), Data
modified after Evernden and Kistler (1970).
Figure },h . Mesozoic time scale with
corresponding intrusive epochs in the
Sierra Nevada region
47
rock near intrusive contacts (Figure 35) ;
apophyses are locally present near intru-
sive margins.
The Merrimac pluton intrudes melange
along the northeastern margin of the
area. This pluton intruded subparallel
with the regional foliation in melange
country rock.
Thermal low-shear metamorphism forms
aureoles in country rock surrounding
Sierran plutons. Country rock around
the Bald Rock and Swedes Flat plutons
is thermally recrystallized by amphibo-
lite facies metamorphism in a 1 to 3 km
(0.6 to 1.8 mi) wide aureole (Compton,
1955). A contact aureole around the
Merrimac pluton, also of amphibolite
facies metamorphism and up to 4 km
(2.5 mi) wide (Hietanen, 1977), is dev-
developed in melange.
Lithologic Description; Plutons in the
area have textures, mineralogies and
ages that are typical of the Sierran
intrusive complex. Rock types forming
plutons include tonalite, granodiorite
and quartz monzonite. Trondhjemite com-
monly forms the central portion of
local plutons. Aplitic and pegmatitic
dikes, representing late-stage intrusive
rocks, are in places abundant near in-
trusive margins.
The Merrimac pluton is primarily
medium- to coarse- grained granodiorite.
Mineralogy of the pluton includes zoned
and unzoned plagioclase (An„^ to An,_) ,
quartz, potassium feldspar and ferro-
magnesian minerals (biotite and horn-
blende) . Accessory trace minerals in-
clude apatite, epidote, muscovite,
sphene and zircon.
The Bald Rock pluton, a well-foliated
compos it ionally-zoned intrusion, is a
mixture of medium- to coarse-grained
granodiorite, tonalite and trondhjemite.
Tonalite and granodiorite are concen-
trated in outer margins of the pluton;
trondhjemite forms the core of the
complex. Stoping, assimilation and sub-
Figure'35. Metavolcanic xenoliths within Swedes Flat plutonic rock in Woodman
Ravine, 6 km (3-5 mi) east of Oroville Dam.
48
Figure 36. View west-northwest of Bald
Berry Creek, Rocks exhibit surface ex
of the Sierran batholithic complex.
sequent contamination is responsible for
compositional layering in the Bald Rock
pluton (Compton, 1955) . Tonalite and
granodiorite include quartz, plagioclase
(An„e to An_„), microcline, hornblende,
biotite, ana accessory metallic minerals.
Common minerals in trondhjemite are
plagioclase (An„ to An„„), quartz, potas-
sium feldspar and muscovite; ferromag-
nesian minerals are rare.
Flow structure is well developed in the
Bald Rocl<. pluton. Flow banding dips
steeply eastward and is defined by a
planar parallelism of biotite, horn-
blende and, to a lesser extent, plagio-
clase. It is most strongly observable
near intrusive margins where mafic
minerals are concentrated. Flow layer-
ing toward the center of the pluton
maintains an easterly dip and is more
concentric than along its margins
(Compton, 1955).
Rock (foreground) 6 km (3.8 mi) east of
posure and exfoliation that is typical
The Swedes Flat pluton is predominantly
tonalite and granodiorite. Gabbro and
diorite are present in subordinate
amounts at the north and south ends of
the pluton. Granophyric rock, as dikes
and inclusion-charged masses, is abun-
dant along the western margin of the
pluton. Common minerals in Swedes Flat
tonalite and granodiorite include saus-
suritized plagioclase (An2Q to An^^),
alkali feldspar, quartz, hornblende and
biotite. Common accessory trace miner-
als are epidote, apatite and, in
places, sphene.
Origin of Sierra Nevada Plutons; Tona-
lite and monzonite plutons in the study
area (Figure 36) are similar in appear-
ance, mineralogy and mode of origin to
those comprising the Sierra Nevada
batholith. Plate tectonic models devel-
oped during the late 1960 's and early
1970's provide new interpretations for
49
the large-scale origin of plutonic
complexes. In both oceanic and
continental-margin settings, voluminous
calc-alkaline magmas are formed above
Benioff zones 150 to 500 km (93 to
124 mi) from the trench axis (Dickinson
and Hatherton, 1967; Dickinson, 1968)
and provide a tectonic model for Sierran
plutonism.
An east-dipping Benioff zone was adja-
cent to the western coast of North
America during much of Phanerozoic time
(Hamilton, 1969; Burchfiel and Davis,
1972, 1975); inclination of the subduc-
tion zone is substantiated by potassium-
silicon ratios in Mesozoic granitic
rocks of California that increase east-
ward (Moore, 1959; Bateman and others,
1963; Dickinson, 1969) with a correspond-
ing depth to the ancestral Benioff zone.
Eastward subduction and partial melting
of lithosphere at depth generated magmas
(plutons) that rose to shallower struc-
tural levels beneath Mesozoic California.
The calc-alkaline plutons were tension-
ally faulted, uplifted, and unroofed in
Cenozoic time. These processes are cur-
rently active and have erosionally
removed more than 8 km (5 mi) of roof
rock (Bateman and Wahrhaftig, 1966) to
expose the plutons.
Superjacent Series Rocks
Chico Formation
Previous Investigations and Age; Sand-
stone, shale and conglomerate of the
Chico Formation were first described and
named by Gabb (1869, p. 129). Diller
and Stanton (1894) used the term "Chico
group" in their study of these rocks;
they considered all Cretaceous deposits
in California part of the "Shasta-Chico
series". Stanton (1896, p. 1,013) for-
mally suggested the name "Chico group"
to describe type-locality exposures
along Chico Creek. Subsequent workers
(Turner, 1896; Bryan, 1923; Brewer, 1930;
Anderson, 1933; Taff and others, 1940;
Popenoe, 1943; Creely, 1955, 1965) have
described members and index fossils
that characterize Chico Formation.
Fossils in the Chico Formation are
abundant and provide accurate strati-
graphic control. Fossils indicate that
the age of the Chico Formation is Upper
Cretaceous (Taff and others, 1940;
Creely, 1965).
Contact Relationships: Basal contacts
of Chico rocks are described as angu-
larly unconformable in the Sierran foot-
hills (Taff and others, 1940). The base
of Chico Formation is not exposed in the
study area, therefore, total thickness
of the formation is uncertain. The
thickest sequence in the study area in-
cludes 20 m (65 ft) of section.
Upper portions of Chico Formation in
the project area are eroded and uncon-
formably overlain by the Tertiary lone I
and Tuscan Formations. West- and
southwest-dipping strata in rocks above
and below the erosional surface are
slightly discordant and actually form
a disconformity between Cretaceous and
Tertiary rocks.
Lithologic Description; Cretaceous I
marine sedimentary rocks, representing
arc-trench gap deposits (Dickenson,
1969), are regionally exposed at margins
of the Central Valley of California and
represent the base of Superjacent Series
deposition. Chico Formation is the old-
est Superjacent Series formation in the
project area.
Chico Formation in the study area is
predominantly a fine- to medium-grained,
fossil-rich, friable sandstone (arkose);
siltstone and pebble to cobble conglomer-
atic lenses occur locally. Fresh Chico
Formation is light- to dark-buff to
dark-gray; weathered exposures have
orangish hues and are lighter in color
than fresh rocks. Bedding, including
abundant cross-beds, is thin to thick
and well-defined.
Arkosic beds of the Chico Formation are
moderately- to well-sorted and poorly
cemented by calcite and clay. Indi-
vidual clastic grains, forming arkosic
50
beds, are angular to subangular. Com-
position of grains includes quartz,
feldspar (plagioclase and potassium
feldspar) and rock fragments (primarily
metamorphic clasts); accessory ferro-
magnesian minerals include biotite,
hornblende, epidote, clinozoisite and
muscovite.
Pebble- to cobble-sized clasts are well-
rounded to sub-rounded and locally form
interbeds in finer-grained sediments.
These clasts include light to dark chert,
quartzite, altered plutonic rocks and
metavolcanic rocks. Conglomeratic beds,
commonly containing an abundance of shell
debris, are usually well-indurated by
calcite cement.
lone Formation
Previous Investigations and Age; The
lone Formation was named and first des-
cribed by Lindgren (1894, p. 3) who
assigned exposures near lone, California
as the type locality. Early investiga-
tions of Tertiary sandstone near Oroville
were by Lindgren (1911) and Dickerson
(1916) . Subsequent detailed studies are
by Allen (1929) and Creely (1965).
The age of lone Formation is substan-
tiated by fossil fauna and flora col-
lected by many earlier researchers.
These fossils indicate that lone depo-
sition occurred in Middle Eocene time.
Contact Relationships: The lone Forma-
tion rests unconformably on the under-
lying formations. lone deposits dip
gently west and southwest and overlie
arc, melange and the Chico Formation in
the study area.
Upper sequences of the lone Formation
include auriferous gravel and tuffaceous
sediment and are conformably overlain by
Lovejoy basalt. Basalt extrusion was
during late stages of lone aggradation;
therefore, the unconformity formed by
basalt at the top of the lone Formation
is a matter of convention.
Auriferous gravel and Oroville tuff
(Mehrten Formation-?) are gradational
in upper portions of the lone Formation.
Auriferous gravel and tuffaceous sedi-
ment, transported and deposited by lone
fluvial processess, are mapped as forma-
tional members in this study. Creely
(1965) mapped quartz-rich sequences as
"auriferous gravels" and tuffaceous rock
as "Mehrten (?) Formation". Mehrten
Formation in the Stanislaus drainage is
dated by Dalrymple (1964) at 8.8 to 9.3
million years while tuffaceous deposits
on South Table Mountain are pre-Lovejoy
basalt (23 million years old) and
older than Dalrymple 's dated Mehrten
Formation.
Tuffaceous beds are locally exposed
through the Oroville area. These tuffs
do not expose basal contacts and are
overlain by late Cenozoic gravels. Such
contact relationships provide no strati-
graphic correlation with tuffs exposed
on North and South Table Mountains which
are topographically higher.
Lithologic Description - lone Formation
Undifferentiated: White to yellowish-
white, medium- to fine-grained, silty-
clayey sandstone constitutes the great-
est percentage of the lone Formation in
the study area; intercalated in sand-
stone are subordinate amounts of silt-
stone, shale, conglomerate and minor
quantities of lignitic coal. Conglome-
ratic beds and pebble stringers are in
most places composed of well-rounded
quartz and chert pebbles. Bedding in
sandstone is thick to thin and
moderately- to poorly-defined; cross-
bedding is common and best observed in
cut slopes.
Most sandstone is friable, argillace-
ous and cemented by interstitial silt
and clay. Individual sand grains are
angular to subangular and composed of
quartz, plagioclase, potassium feldspar
and rock fragments. Trace amounts of
heavy minerals include hematite, magne-
tite, epidote, zircon, hornblende, tour-
maline and clinozoisite.
Lithologic Description - Auriferous
51
Gravel; Auriferous (gold bearing) gra-
vel contains high percentages of white
quartz-rich sand and gravel. In the
Oroville area this gravel has a maximum
thickness of 100 m (330 ft) and is ex-
posed by numerous hydraulic mines cut
into side slopes of North and South Table
Mountains (Figure 37) .
Sand in gravel is medium- to coarse-
grained, sub- to well-rounded and exhib-
its fair sorting. Individual sandstone
layers are thin- to thickly-bedded and
manifested by slight variations in grain
size, the presence of thin siltstone or
pebble conglomerate lenses and thin
mica-clay layers.
Conglomeratic sections are composed of
subrounded to well-rounded quartz peb-
bles and cobbles. Clasts are loosely
packed and set in a quartz-sand matrix.
Individual conglomerate beds range from
thin pebble stringers in sandstone to
layers more than 1 m (3 ft) thick.
Lithologic Description - Oroville Tuff
(Mehrten Formation-?); Tuffaceous de-
posits include fine-grained clayey beds
(relict ash); tuff clasts in coarse-
grained, water-lain and cross-bedded
deposits; white, fine-grained, sandy
beds; and moderately- to well-cemented
volcanic mudflow breccia. All of
these rock types, including clay lay-
era, which possibly represent an air-
lain derivation, were eroded and trans-
ported from sources to the east and
north.
Light colored and cross-bedded, sandy,
tuffaceous sequences are locally exposed
around Oroville and represent fluvial
deposition. Whether separated tuffa-
ceous outcrops represent rock- or time-
I
/*
r
■■«>*.
Figure 37- lone Formation auriferous gravel
(Mehrten Formation-?) in a hydraulic mining cut on the east side of
Table Mountain.
52
stratigraphic horizons is vmcertain.
Mudflow volcanic breccia is formed by
angular to sub-angular, vesiculated and
amygdaloidal rhyodacite clasts set in a
reddish-brown, sandy-silty matrix. Brec-
ciated clasts are not locally derived.
Source areas of the lone Foinnation sug-
gest the mudflow breccias were also de-
rived from east and north of the area.
Love joy Formation
Previous Investigations and Age; The
basalt on Oroville Table Mountain was
first mapped and named "older basalt"
by Turner (1894) to differentiate the
unit from younger flows in the area.
This basalt was correlated with the
Lovejoy Formation by Durrell (1959b,
1966) which he considered, based on
stratigraphic relationships, to be of
Eocene age and derived from areas east
of the present Sierra Nevada crest.
Dalrymple (1964) radiometrically dated
rocks above and below Lovejoy Formation
and determined the age of basalt to be
Early Miocene; his oldest date, 23 mil-
lion years, was obtained from a tuff
bed below Lovejoy Formation on South
Table Mountain and should be a maximum
age for basalt in this area.
Contact Relationships; Lovejoy Forma-
tion in the study area disconformably
overlies lone Formation and Oroville
tuff (Mehrten Formation-?) (Figure 38);
basalt rests unconformably on ophiolite
and melange in two localized areas but
this relationship is not common. Lower
contacts of basalt are nearly planar and
dip 2 to 3 degrees west-southwest. Upper
and lower planar contacts indicate that
the basalt has experienced little defor-
mation during regional westward tilting
and provide control for post-extrusive
(late Cenozoic) faulting.
Figure 38. View south of Lovejoy Formation basalt disconformably overlying
lone Formation sedimentary rock in hydraulic cut face of the Cherokee Mine.
53
Figure 39. View east from upper reaches of Morris Ravine of Lovejoy Formation
basalt on North Table Mountain. Basalt at this location has a minimum thick-
ness of 75 m {2hG ft) and rests d i sconformably on lone Formation.
Lithologic Description; Lovejoy Forma-
tion forms the flat-topped mesas of
North and South Table Mountains
(Figure 39). Lovejoy basalt includes
one or more sub-horizontal flows with a
cummulative thickness in the Oroville
area of less than 50 m (164 ft).
Lovejoy basalt is dark-brown to black
and forms blocky outcrops. Poorly-
developed columnar jointing is common in
upper parts of the formation. Lower
parts of the formation are generally
fragmented and locally include a basal
conglomerate. Vesiculated basalt is
more abundant near the base of the for-
mation. Basalt mineralogy includes
plagioclase (An,e to An , _) , olivine and
traces of augite. Plagioclase microlites
are abundant in some samples. A crystal-
line to glassy matrix comprises the
54
greatest volume of basalt. .
Tuscan Formation
Previous Investigations and Age; Rocks
of the Tuscan Formation were first des-
cribed by Whitney (1865). Diller (1892,
1895) named the formation and described
the type locality at Tuscan Springs in
Tehama County.
Anderson (1933) published a comprehen-
sive paper on the Tuscan Formation.
This work includes many detailed rock
descriptions and a discussion on the
development of Tuscan breccia.
Recent studies of the Tuscan Formation
are by Creely (1965) and Lydon (1968).
Lydon's work is comprehensive and deals
with the source areas for the rocks.
Tuscan Formation is Late Pliocene in
age (Lydon, 1968). A potassium-argon
age of 3.3 million years (Evernden and
others, 1964) is determined for the
Nomlaki Tuff member of the formation.
Contact Relationships; The Tuscan For-
mation unconformably overlies melange
in the study area; locally Tuscan rocks
rest disconformably on Chico and lone
Formations. Basal contacts of Tuscan
Formation indicate the depositional sur-
face is relatively flat and dips slightly
to the southwest. This horizon trends
below alluvium of the Sacramento Valley.
Upper surfaces of Tuscan flows are rela-
tively planar (Figure 40) and dip at low
angles to the southwest. These flows
are deeply incised by westerly flowing
drainages.
Lithologic Description; The volcanic
Tuscan Formation is composed of lahars,
volcanic sand, conglomerate, tuff, tuff
breccia, and intercalated andesite and
basalt flows. These rocks when fresh
are gray, purple, orange or brown. The
maximum formational thickness in the
study area is 180 m (590 ft) .
Tuff breccia (lahar) forms about 75 per-
cent of the formation. Clasts are
basalt and andesite with basalt being
predominant (Anderson, 1933). Flow brec-
cias are unsorted and form irregular
contacts with underlying rocks. The
matrix of these rocks is well-indurated
volcanic and tuffaceous sand. Interca-
lated flow rocks, a minor component of
the Tuscan Formation, are predominantly
olivine basalt and pyroxene andesite.
METAMORPHIC SURFACE
TUSCAN SURFACE
Ik'^vifcv
Figure ^0. View north of lower and younger erosional surface on Upper Pliocene
Tuscan Formation that is separated by the West Branch of the Feather River
(not shown) from an older and structurally higher erosional surface cut into
Mesozoic metamorphic rocks. Photograph taken from intersection of Highway 70
and Messilla Valley Road (Cherokee quadrangle).
55
Tuff, tuffaceous sandstone and volcanic
sandstone are locally intercalated with
the flows and breccias. These units are
composed of angular crystal and lithic
volcanic fragments with andesitic to
basaltic compositions. Sequences are
well-bedded, well-sorted, and commonly
cross-bedded (Figure 41) . Sediments
are common at the western margins of the
formation. Tuff breccia dominates the
stratigraphically thicker eastern areas
of Tuscan exposure.
Late Cenozoic Gravels
Previous Investigations: Late Cenozoic
fluvial deposits of the Oroville area
were first differentiated by Creely
(1965). He assigned all older gravels
in the area to the Pleistocene Red Bluff
Formation.
Recent mapping in the Bangor quadrangle
(Quintin Aune, unpub. data) indicates
there are several gravel units of vary-
ing ages and source areas. Mapping for
this study confirms the presence of mul-
tiple gravels that probably are not time
equivalent to the Red Bluff Formation.
Therefore, they are named "late Cenozoic
gravels" rather than Red Bluff Formation
in this report.
Contact Relationships; Late Cenozoic
gravels overlie both Basement Series
rocks and Superjacent Series rocks in
the project area. They are separated
from basement rocks by an angular uncon-
formity and from superjacent rocks by a
disconf ormity .
Figure 41. Tuscan Formation volcanic conclomerate, cross-bedded sand and
laharic mudflow breccia along Sycamore Creek 3 km (2 mi) northeast of Chico.
56
Figure hi. Late Cenozoic gravel and cross-bedded sand (Red Bluff Formation-?]
exposed in a railroad cut 0.5 km (0.3 rni) south of intersection of Baggett
Palermo and Baggett Marysville Roads (Palermo quadrangle).
Lithologic Description; Late Cenozoic
gravels in the study area have a maximum
thickness of 30 m (100 ft) and are com-
posed of poorly-sorted, rounded to sub-
rounded, pebble- to boulder-sized clasts.
These are weakly to moderately cemented
by varying amounts of clay, silt and
orange amorphous silica; cementation is
weak where sandy and moderate in clayey
sections. Clast types, in descending
order of abundance, are metavolcanic
rock (including ophiolite, arc and
younger dike rocks), intrusive rocks,
and fine-grained porphyritic volcanic
and siliceous clasts (including quartz,
quartzite and red and black chert).
Imbricate pebbles indicate source areas
are to the north and east. Well-sorted
and cross-bedded, weakly-cemented sand,
and thin-bedded, moderately indurated
silt and clay comprise the gravel matrix.
Sandy members of gravels are generally
thinly- to moderately-bedded, lenticular
and, in places, cross-bedded (Figure 42).
Fine-grained sands and silty-clayey mem-
bers, most common away from upland ter-
ranes, probably represent flood plain
deposits of the ancestral Feather River
and associated tributaries.
Clayey sections in gravel have minor
occurrences in the study area. Clay in
gravel sequences, probably reworked from
underlying tuff units (Figure 43), repre-
sents low energy deposition.
Quaternary Landslides
Our investigation indicates that large-
scale landsliding is more common in the
project area than suggested by earlier
detailed investigations. Failures com-
57
monly occur from slopes underlain by
lone Formation (Figure 44); this forma-
tion is the least competent of study
area rock types.
North and South Table Mountains and the
Campbell Hills are capped by Lovejoy
basalt and have side-slopes underlain by
gently west-dipping lone Formation;
south- and west-facing slopes in these
areas daylight lone bedding. Resistant
cap rock overlying non-resistant lone
Formation provides ideal conditions for
large-scale landsliding. In this situa-
tion, side-slopes are oversteepened by
artificial support of the erosionally-
resistant cap rock. A regional slope-
stability study of the United States
notes the western side-slopes of North
and South Table Mountains at Oroville
are highly susceptible to failure
(Radbruch-Hall and others, 1976).
Landslides were not mapped in detail
on Table Mountain or Campbell Hill side-
slopes for this study. The time requir-
ed for mapping gravity-induced struc-
tural complexities was not warranted for
purposes of this investigation; there-
fore, landslides probably underlie more
area than is indicated by our geologic map.
Numerous landslides occur along the
Feather River and its major forks. Fail-
ures in this area are within arc and
ophiolitic lithologies. - The toe por-
tions of these landslides occur near
lower valley slopes and are now season-
ally inundated by Lake Oroville. Land-
slide movements are mostly prehistoric,
however, several failures indicate re-
cent activity. The largest recent land-
slide is superimposed on an older fail-
ure that moved from the northwest side
of Stringtown Mountain (Figure 45).
Figure ^43. Late Cenozoic gravel (Red Bluff Formation-?) unconformabl y overlying
Oroville tuff (Mehrten Formation-?) along the Feather River 1.0 km (0.6 mi) west-
southwest of Oroville.
58
Figure 44. View west of landslide in lone Formation. Note the vegetation stand
in graben area of landslide. Location is in Campbell Hills just north of
Thermalito Forebay by Highway 70 (center).
Figure 45. Aerial southeast view of Stririgtown Mountain landslides. Note that
the recent failure is superposed on a larger and older landslide.
59
\
i
Figure 46. Aerial east-southeast view of a prehistoric landslide that is part
of a much larger failure involving the entire north slope of Bloomer Hill into
the North Fork of the Feather River.
60
The largest landslide in the project
area, underlying the north slope of
Bloomer Hill, is a failure of arc rock
into the North Fork of the Feather River
(Figure 46). The landslide moved north
as a large slump of several individual
failures. This landslide could have
temporarily dammed the river. Arcuate
scars of disturbed arc rock define the
landslide boundaries which are best ob-
served using high-altitude aerial
photographs.
STRUCTURAL GEOLOGY
Faults
Geologic evidence in the northern
Sierran foothills suggests two periods of
fault activity. The first episode of
faulting was from compression before
Late Jurassic time. This deformation
occurred prior to the intrusion of local
plutons (Nevadan orogeny-Yosemite intru-
sive epoch) . The second period of
faulting began in late Tertiary time and
continues to the present. The late Ter-
tiary to present tectonic regime is one
of east-west extension which places older
fault zones in tension. As a result,
some recent movements have occurred along
older Mesozoic faults. Other movements
displace Tertiary rocks and have thus
broken new ground, possibly from reacti-
vation of underlying Mesozoic faults.
Data on foothills faulting between
Oroville and Sonora is derived largely
from exploration trenches by Department
of Water Resources and other agencies.
Locations of exploration trenches on ma-
jor lineaments are shown in Figure 47
and findings are summarized in Table 1.
BASE MAO
WOODWARD
MODIFIED AFTER /
YOE CONSULTANTS f
Figure Ul . Major lineaments in the northwestern
Sierran foothills showing exploration localities
with faulting assessments for each site.
61
TABLE 1
EXPLORATION TRENCHES IN FOOTHILL BELT - OROVILLE TO AUBURN AREA
(Exploration sites listed from north to south on given lineaments)
Lineament ,
Agency, and
Trench Number
SWAIN RAVINE LINEAMENT
Faulting
Exposed
Attitude
Cenozoic
Movement
No
No
Yes
No
Yes
No
Yes
N10-40W, 60-73SW
N12W, 65SW
NlOW, 69SW
N20W. 70SW
N15W, 65SW
Yes Trench located on crack; faulting
does not offset soil-bedrock inter-
face.
Yes Fault does not offset bedrock-soil
interface .
Yes Trench located on crack; faulting
does not offset bedrock-soil inter-
face.
Yes Trench located on crack; faulting
does not offset bedrock-soil inter-
face .
Yes Trench located on crack; faulting
offsets gravel-soil contact 30 mm.
? Faulting does not offset bedrock-
soil contact.
N9W. 54SW
USCE (WCC)
Grubbs 1
PGandE (WCC)
Grubbs 2
PGandE (WCC)
Sims 1
USCE (WCC)
Cleve. Hill 1 & 2
PGandE (WCC)
Lorraine 1 & 2
Trench located on crack; faulting
does not offset bedrock-soil inter-
face .
Trench located on East Mission
Olive crack zone.
Trench located on East Mission
Olive crack zone.
Trench located on West Mission
Olive crack zone.
Trenches located on northern end
of Cleveland Hill Fault; bedrock
fault with at least 3 episodes
of displacement described.
Trenches located on eastern splay
of Cleveland Hill Fault.
PGandE (WCC)
Cleve. Hill 3
USER (WCC)
Orange Road 1-9
PGandE
WCC)
Pace
1-5
USCE
4F-1
USCE
4F-2
4F-3
N11-21E, 55-59SE;
N18-20W, 80NE
Yes
NSW,
41NE,
N15W
4 7NE
No
__
Yes
N15W
46NE
Yes
N2E,
52SE,
N22W
48SW
Yes
N32W
70NE
N34W
70SW
Trenches located on Cleveland Hill
Fault at southwest margin of
Cleveland Hill.
Trench located on Cleveland Hill
Fault at southwest margin of
Cleveland Hill.
Faults located in trenches 2, 3, 4,
5,6,9
Faulting does not offset bedrock-
soil interface.
Faulting does not offset bedrock-
soil interface.
Faulting does not offset bedrock-
soil interface.
Faulting does not offset bedrock-
soil interface.
Faulting does not offset bedrock-
soil interface.
62
TABLE 1 (Continued)
Lineament,
Agency, and
Trench Number
PAYNES PEAK LINEAMENT
PGandE (WCC)
Knapp No. 1
PGandE (WCC)
Burt No. 1 & 2
Faulting
Exposed
Yes
Yes
Cenozoic
Movement
No
No
Faulting does not continue into
overlying soils.
PRAIRIE CREEK LINEAMENT
DWR 18 No
PGandE (WCC)
O'Brien No
PGand E (WCC)
Wilson No. 1 & 2 Yes
No
No
No faults exposed and trench not
logged.
Faulting does not continue into
overlying soils.
SPENCEVILLE LINEAMENT (Southern extension of Prairie Ck . Line.)
US BR (WCC)
Spenceville 1 Yes N32W, 63SW;
(5 trenches) N55W, 67SW
2 Yes
Yes
No
Yes N15-50W, 70-75SW Yes
No - - No
No — No
Faulting continues into overlying
soils .
Faulting does not continue into
overlying soils.
Faulting displaces paleo B.
DEADKAN LINEAMENT (Southern extension of Spenceville and Prairie Ck . Line.)
USER (WCC)
Henriques & Wilson Yes N20W, 47SW
(10 test pits) N20W, 55SW
No fault assessment made because
paleo B too scarse in local area
for evaluation
DEWITT LINEAMENT
USBR (WCC)
Hubbard Road
(2 trenches)
USBR (WCC)
Bean Road
(1 trench)
)R (WCC)
St. Joseph
( 3 trenches )
N44-50W, 50-60SW Yes ( ? )
N60W, 65NE
N38W, 60NE
Faulting in paleo B but gravity
also affects rocks making inter-
pretations difficult; faulting
classified (USBR criteria)
"indeterminate" (active).
Faulting does not continue upward
into paleo B; faults classified
(USBR criteria) "indeterminate"
( inactive ) .
Paleo B locally scarce, therefore,
faulting at this locality classi-
fied (USBR criteria) "indeterminate"
MAIDU LINEAMENT
USBR (WCC)
Radio Tower (Located
on E. splay of Maidu
Line. )
(6 trenches)
USBR (WCC)
Maidu
(2 trenches)
(4 test pits)
N55-60E, 30NW-90 ?
NIOE, 45NW
Paleo B and overlying soils
locally scarce, therefore, faulting
at this locality classified (USBR
criteris) "indeterminate".
Paleo B and overlying soils locally
scarce, therefore, no fault
assessment made for Late Cenozoic
tectonics at this locality.
63
TABLE 1 (Continued)
Lineament,
Agency, and
Trench Number
USER (WCC)
Maidu East
(E splay of Maidu
Line. )
( 5 trenches by WCC
plus 25 trenches
and backhoe pits
by USER)
Faulting
Exposed
Cenozoic
Movement
N13E, 77SE,
N55W, 47SW,
N3E, 67SE,
N30W, 67SW,
N20-25E, 82NW-90,
N20-30E, 72-80NW
PILOT HILL LINEAMENT
USER (WCC)
Pilot Hill
( 3 test pits )
USER (WCC)
Salmon Falls
(4 test pits)
SALT CREEK LINEAMENT
No(?)
Maximum vertical separation of
Mehrten Fm. across fault zone is
5.4 m (18 ft). Slickensides in
soil with orientations similar t
to bedrock faults and steps in
colluvial base overlying bedrock
fault traces indicate faulting
is Cenozoic. To north a buried
paleosol at least 100,000 years
old is not cut by faulting;
therefore, movements are too small
to offset soils or fault displace-
ments die out to north. Faulting
confidence level is 2 on 0-10
scale .
Paleo E and overlying soils scarce,
therefore, no fault assessment made
for this locality.
Thin shears exposed but no faults;
lack of local paleo B for offset
control. No fault assessment.
USER (WCC)
Salt Creek
( 10 test pits)
USER (WCC)
Bayley House
( 3 trenches )
( 12 test pits)
RESCUE LINEAMENT
USSR (WCC)
Luneman Road
( 3 trenches )
N54, 60SW
N40W, 40NE
USER (WCC)
Knolls
(1 trench)
N20W, 50SW
Paleo B locally lacking, therefore,
no fault assessment made for this
area .
Ground water barriers define the
lineament but are controlled by
clay-rich weathering zones; no
evidence of Cenozoic faulting noted.
Faulting trends into overlying
colluvium and terminates a
paleo E with colluvium on east
side of fault thicker than on
west side; paleosol indicates
0.55 m (1.8 ft) of down to east
displacement. Fault in trench
3 classified as "indeterminate"
(active) by USER criteria;
confidence level is 4 on scale
0-10.
Distinct lithologic blocks are
bounded in places by clay seams
that appear to juxtapose the
blocks; basal contact is not
obviously offset. Faulting
classified by USER criteria as
"indeterminate" (active).
Confidence level is 2 on scale of
0-10.
64
Mesozoic Faults - Northern Foothills
Clark (1960) identified and named the
Foothills Fault System (Figure 48).
This system, bounded by the Melones
Fault zone on the east and the Bear
Mountains Fault zone on the west, is '
formed by numerous north to north-
northwest trending preintrusive reverse
faults (Clark, 1964, 1976). Major faults
within this system can be identified by
elongate bodies of serpentine, areas of
structural and lithologic discontinuity
and zones of intense and well-defined
shear cleavage that dip steeply east.
Subsequent to Clark's initial study,
Mesozoic faults in the foothills were
described and mapped in many geologic
investigations. A few of these studies
include works by Baird (1962), Burnett
and Jennings (1962) , Bateman and others
(1963), Clark (1964, 1976), Creely (1965),
Cebull (1972) and Hietanen (1973a, 1976,
1977).
The Melones Fault zone, named by Clark
(1960), strikes northwest along the east-
ern margin of the Foothills Fault System
in its type locality. The fault is de-
fined by strongly sheared zones that, in
places, incorporate serpentine and blocks
of undeformed or less deformed rock.
Shear cleavage within the zone is local-
ly several hundred metres wide and dips
vertically or steeply east (Clark, 1960,
1964).
The Melones Fault zone, best exposed
south of the Cosumnes River, is the east-
ern limit of the Foothills Fault System
(Jennings, 1975). Clark (1960) noted
that north of the American River the
Melones Fault splits into several zones.
The splay representing the Melones Fault
zone in this area is defined as the
boimdary between Paleozoic rocks to the
east and Mesozoic rocks to the west
(Clark, 1960, 1964; Duffield and Sharp,
1975).
The Bear Mountains Fault zone of Clark
(1960) parallels the trend of the Melones
Fault zone to the east and splits into
several faults at its northern end near
the Cosumnes River. The regional shear
zone mapped by Burnett and Jennings
(1962) to the southwest of the area may
represent the northern extension of the
Bear Mountains Fault zone. This fault
zone averages a few hundred metres in
width and dips vertically or steeply
east (Clark, 1964). Net displacement
across the system is unknown byt suggested
to be large and probably represents sev-
eral thousand metres of offset (Clark,
1964).
Origin of the Bear Mountains Fault, as
with other faults in the Foothills Fault
System, is the result of eastward under-
thrusting during Farallon-American plate
interactions in Late Jurassic time. East-
ward underthrusting is suggested by some
early researchers (Ferguson and Gannet,
1932, p. 90; Knopf, 1929, p. 45-46); how-
ever, a strike-slip motion, at least in
part, is indicated by Clark (1960) and
Cebull (1972).
Mesozoic faults in the study area are
considered to be part of the Foothills
Fault System. These faults displace the
late Oxfordian to early Kimmeridgian
(Imlay, 1961, p. D8-D9) Monte de Oro
Formation and are truncated by Sierran
plutons of the Yosemite intrusive epoch.
Radiometric dating of the plutons (Gromme
and others, 1967; Evemden and Kistler,
1970) yield a minimum age of about
130 million years. These data suggest
that Mesozoic faults developed during
the Late Jurassic-Early Cretaceous
Nevadan orogeny, about 130 million years
ago.
Foothills system faults were driven
by a regional east-west compression and
are synchronous with late stages of an
epidote-albite-amphibole metamorphism.
Compressive stresses and subsequent
Foothills Fault System displacements were
generated during subduction underthrust-
\ ing and accretion of arc and ophiolitic
^ rocks to Mesozoic California. This de-
formation generated north-striking,
steeply dipping faults, fold axes and
slaty cleavage in rocks of the study
65
Data modified after Clark (I960).
Figure h8. Foothills Fault System of the western Sierra Nevada, California
66
area. Deformation ceased when these
rocks were firmly accreted (obducted) to
the continent. Additionally, the west-
erly migration of subduction was stabi-
lized in areas of the present Coast
Ranges terrane at this time.
Mesozoic Faults - Project Area
Mesozoic faults in the study area com-
monly appear as photo lineaments. These
lineaments, sharply defined in high-
altitude photography, are commonly
aligned with foliation and fold axes
in foothill rocks.
Field investigations of major lineaments
indicate three are fault zones. Fault
features include: (1) pronounced align-
ment of ridges and valleys along linea-
ment trends, (2) sheared rocks and
numerous subordinate faults and shears
subparallel with major lineaments, and
(3) springs and seeps.
Mesozoic fault movements were probably
oblique, however, a large reverse compo-
nent is indicated by many researchers
(Hamilton, 1969; Schweickert and Cowan,
1975; Clark, 1976; Russel, 1978;
Standlee, 1978), Reverse, east-dipping
Mesozoic faults are predictable in mo-
dels of eastward subduction which was
active at this time; the Glover Ridge
thrust fault, an obduction suture, is
an exception.
Plate tectonic models for explaining
the origin of Mesozoic foothills faults
suggest large-scale movements. Displace-
ments on larger foothills system faults
such as the Melones Fault zone may ex-
ceed several kilometres.
In summary, the Foothills Fault System
is a late Paleozoic to Late Jurassic
feature. Compression driving these
generation faults originated from epi-
sodes of plate convergence and consump-
tion along the western edge of Mesozoic
North America, and produced major struc-
tural elements of the Sierran foothills.
Swain Ravine, Paynes Peak and Prairie
Creek Lineament/Fault Zones; The Paynes
Peak and Swain Ravine Lineaments are the
most striking photo lineaments in the
area. Another prominent lineament, the
Prairie Creek Lineament, projects into
the study area from the south, west of
the Swain Ravine Lineament . The trace
of the Prairie Creek Lineament within
the study area is not well defined.
The Swain Ravine and Paynes Peak
Lineaments trend approximately north-
northwest and parallel each other in the
southern field area. The two lineaments
can be traced on the ground by aligned
valleys, discontinuous areas of sheared
rocks, springs and seeps, and are inter-
preted to be Mesozoic fault zones.
The Paynes Peak Lineament in the study
area has a strong to moderate expression.
It lies parallel to, and about 1.6 km
(1 mi) east of the Swain Ravine Linea-
ment. Surfically, the only conclusive
fault features are exposed in Rocky
Honcut Creek (Bangor quadrangle.
Section 16, T18N, R5E) where a break in
outcrops, a linear drainage and aligned
springs define the fault trace.
The northern extension of the Paynes
Peak Lineament trends just east of
Miners Ranch Reservoir and Bidwell Canyon
Saddle Dam. Rock along the lineament is
strongly sheared, however, field evi-
dence for faulting north of Rocky Honcut
Creek is poor. The Paynes Peak Lineament,
as defined in this report, coincides
with the eastern margin of the "regional
shear zone" as mapped by the U. S. Army
Corps of Engineers (1977, Plate V) and
terminates about 1 km (0.6 mi) northeast
of Bidwell Canyon Saddle Dam.
South of the project area the Paynes
Peak Lineament has a strong topographic
expression. The lineament terminates
north of Paynes Peak in the vicinity of
Stone House (U. S. Army Corps of
Engineers, 1977, Plate IV).
67
Surface and subsurface data along the
Paynes Peak. Lineament were collected and
analyzed by Pacific Gas and Electric
Company and Woodward-Clyde Consultants.
Three trenches, designated Knapp No. 1
and Burt Nos. 1 and 2, were excavated
between Bangor and the Yuba River by
Pacific Gas and Electric Company. These
trenches exposed bedrock faults that do
not displace overlying soils.
The Swain Ravine Lineament is the most
significant lineament in the area because
it coincides with Cleveland Hill Fault
cracking that occurred during the 1975
Oroville earthquake. No cracking along
the lineament is reported south of Bangor;
however, the lineament continues southward
as a strong feature. Just south of the
Yuba River, the lineament coincides with
the eastern margin of a regional shear
zone mapped by Burnett and Jennings (1962)
and the U. S. Army Corps of Engineers
(1977). A more thorough description of
the Swain Ravine Lineament is included
with the section on Cenozoic faults.
The Prairie Creek Lineament has the
least physical expression of the three
major lineaments in the study area. The
lineament, well-developed south of the
Yuba River, is discontinuous to the
north. It is prominent in the southeast
corner of the Palermo quadrangle, but
dies out to the north where the area is
overlain by alluvium and late Cenozoic
gravels. The length of the Prairie
Creek Lineament from the study area to
its southern end, where it is truncated
by the Rocklin pluton, is approximately
64 km (40 mi).
Investigation of the Prairie Creek
Lineament between Bangor and the Yuba
River consisted of field mapping and a
trench (DWR 18) in the Palermo quad-
rangle by Department of Water Resources
(this study) and three trenches by
Pacific Gas and Electric Company. Two
of the Pacific Gas and Electric Company
trenches (Wilson, 1 and 2), located
about 4.8 km (3 mi) northwest of Browns
Valley, exposed bedrock faults which
did not displace overlying soils. The
68
third trench (O'Brien) about 3.2 km
(2 mi) northwest of Loma Rica exposed
no fault "structures.
In November 1977, Department of Water
Resources personnel trenched the north-
ern end of Prairie Creek Lineament about
855 m (2,800 ft) north of Cox Lane
(NEl/4 Section 27, T18N, R4E) . Aligned
bedrock ridges and a small depression
(sag pond-?) define the Prairie Creek
Lineament in this area and suggest it is
a fault. The trench exposed only strong-
ly weathered, undisturbed bedrock and
was backfilled without being logged.
That our trench near Cox Lane and the
O'Brien trench to the south did not ex-
pose faulting may mean that the fault
trends east or west of the exploratory
trenches, or that it does not continue
into this area.
It is assumed the Swain Ravine, Paynes
Peak and Prairie Creek Lineaments are
complex zones of Mesozoic faulting.
These fault zones are probably bands of
small, discontinuous faults. Conclusive
evidence in the way of trenches or clear-
ly exposed faults is not available to
j-iTove that this assumption holds true
throughout the extent of the lineaments,
however, other field evidence indicates
it is a reasonable assumption. The
sense of displacement along these linea-
ments cannot be determined by local field
relationships.
Oregon Gulch Fault: The Oregon Gulch
Fault juxtaposes arc rocks on the west
against ophiolite on the east. The
Fault was first mapped by Creely (1965)
in his study of the area. Schweickert
and Cowan (1975, p. 1,330) show the
fault as a continuation of the Bear
Mountains Fault zone. Our work indicates
this fault is much smaller than the Bear
Mountains Fault and that the two are
probably not physically continuous. They
are, however, interpreted to have formed
during the same period of Mesozoic time.
The Oregon Gulch Fault is traceable for
approximately 29 km (16 mi) on a north-
south trend through the central portion ^
of the area; the fault is obscured lo-
cally along this trend by unconformably-
overlying late Cenozoic terrestrial
gravel and tuff. The fault zone, moder-
ately defined where exposed, is less
than 5 m (16 ft) wide and dips verti-
cally or steeply east. A trench across
the fault exposed juxtaposed arc and
ophiolitic rocks, but the exact contact
was not well-defined (see log. Trench 15
on pages 118-119).
Monte de Pro Fault: The Monte de Oro
Fault, first mapped by Creely (1955), is
exposed for 6 km (4 mi) in an approximate
north-south trend through the central
portion of the area. It is overlain in
its north and south projections by Ter-
tiary Superjacent Series rocks. The
fault dips east and truncates Monte de
Oro Formation against arc rocks on the
east. Quartz is locally intruded into
the fault zone and helps to define its
location in poorly exposed areas.
Unnamed Faults; An unnamed fault,
subparallel with previously described
foothills faults, is exposed 1 km
(0.6 mi) north of Oroville Dam. The
fault is traceable in a north-south
trend for 3 km (2 mi) just west of the
North Fork of the Feather River. Gouge,
aligned valleys and seeps define the
trace.
Small faults and shears are exposed
locally through the area. These faults,
traceable only for short distances,
probably result from sjTnpathetic dis-
placement and fracturing related with
Foothills Fault System activity.
Foothills system faults in melange at
the north end of the area strike approxi-
mately northwest and dip steeply to the
northeast. A reason for the change in
strike of the Foothills Fault System
from north to northwest in this area is
uncertain.
Northern area faults can be differen-
tiated into (1) faults that cut melange
and (2) faults that are associated with
serpentine. Faults associated with ser-
pentine are suggested to represent rem-
nant Benioff zones (Hamilton, 1969;
Bailey and others, 1970; Bateman and
Clark, 1974; Coleman, 1977). Occur-
rences of serpentine were used in this
study to identify the location of such
faults. Faults that cut melange prob-
ably formed at the same time as those
associated with serpentine within the
subduction complex accretionary prism.
Accretionary prism models (after Karig
and Sharman, 1975; Dickinson, 1975)
indicate that large numbers of concor-
dant reverse faults are formed in the
accumulation and development of these
regions. Poor exposure and large areas
of similar rock type that are concordant
with regional trends preclude identifi-
cation and mapping of many pre-Cenozoic
faults in melange terrane; therefore,
the number of these faults shown on the
geologic map (Plate 1) is probably fewer
than those actually present. Extreme
shearing is visible in many melange out-
crops suggesting that faults in this
terrane are numerous and conform to sub-
duction complex models. Faulting within
this complex incorporates and separates
individual blocks of rock that contain
smaller-scale faults concordant with
regional trends.
The amount of offset on faults in melange
is not known. Plate tectonic models of
continued underthrusting at convergent
boundaries suggest cumulative displace-
ments are large and may represent several
kilometres .
Glover Ridge Fault; A major Mesozoic
thrust fault, informally named the
Glover Ridge Fault, is in the south-
eastern Cherokee quadrangle. Glover
Ridge is a klippe (Figure 49) separated
from the main thrust sheet of arc rock
by incised erosion in Vinton Gulch. The
fault was mapped by Creely (1965) as an
intrusive contact, however, clay gouge
between arc rock and underlying melange
indicates a fault, rather than an intru-
sive contact. Approximately 23 km
(14 mi) of fault trace is exposed in
the area (Plate 1) .
The Glover Ridge Fault trends into the
southwestern Berry Creek quadrangle
69
Figure kS.^'^^fla] southeast view of G
location of the Glover Ridge Fault,
photograph.
where its exact location is uncertain.
The fault represents a thrust system
that overrode melange; its presence
should be suspected wherever arc or
ophiolitic rocks overlie melange. Sev-
eral exposures of isolated arc rock in
the Big Bend area are in contact with
melange metasedimentary rocks and may
represent klippen or exotic blocks in-
corporated in melange from partial sub-
duction of the arc complex.
Topographic configuration indicates the
Glover Ridge Fault dips to the south-
west. The contact is nearly flat-lying
in exposed areas but in the subsurface
to the south and west may be more steep-
ly inclined. The Glover Ridge Fault is
interpreted to represent a portion of an
obduction suture along which arc and
ophiolitic rocks were thrust over me-
lange during accretion to continental
terrane.
Extent of the obduction suture is uncer-
tain in the Sierran foothills because
exposures of the contact are limited.
A portion of possibly the same, or a
contemporaneous thrust fault is exposed
70
over Ridge (klippe) and the traced
West Branch Bridge is center-left in
near the Bear River southeast of
Marysville (Xenophontos and Bond, 1978).
Another fault discordant to the Foothill
Fault System is exposed near Box Hall
Flat, approximately 5 km (3 mi) north of
Oroville Dam. The fault, strongly pro-
nounced in aerial photographs and poorly
exposed on the ground, can be traced for
approximately 3 km (2 mi) in a northeast-
southwest direction. Crushed rock and
gouge are exposed locally along the fault
trace. Sense of slip and total offset
on this fault are unknown because fault-
ing is entirely within Smartville ophio-
lite. Development of this fault is
probably synchronous with obduction and
therefore represents late-stage develop-
ment of the Foothills Fault System.
Cenozoic Fault Movement
Cenozoic faulting in the Sierran foot-
hills has been described by several geol-
ogists (Lindgren, 1911; Ferguson and
Gannet, 1932; Durrell, 1959a; Burnett
and Jennings, 1962; Strand and Koenig,
1965; Jennings, 1975, 1977; Alt and
others, 1977). Most of the recognized
Cenozoic faults are northwest-striking,
east-dipping, high-angle, normal faults
(summary in Alt and others, 1977,
pp. 33-35).
Cenozoic fault movements commonly occur
along older, Mesozoic faults (Alt and
others, 1977). Not all Mesozoic faults
have experienced reactivation, but they
must be considered avenues along which
fault movements preferentially occur.
Woodward-Clyde Consultants compiled data
on 46 faults in the northern Sierra
Nevada having evidence for probable late
Cenozoic displacements (Alt and others,
1977). Vertical displacements are unde-
termined for 11 of these faults. For
the remaining faults, vertical displace-
ments are relatively small-scale, ranging
from 0.6 m (2 ft) to about 180 m
(600 ft). In the Oroville area, dis-
placements range from 4.3 m (14 ft) on
the Swain Ravine Lineament fault at the
Orange Road trench site, about 17 km
(11 mi) south of Oroville, to 46 m
(150 ft) on a fault about, 27 km (17 mi)
north of Oroville.
Swain Ravine Lineament Fault Zone:
Cenozoic fault movement in Basement
Series rocks within the Oroville study
area is recognized only in the Swain
Ravine Lineament fault zone. This dis-
placement was first noted after the
August 1975, movement of the Cleveland
Hill Fault. A striking feature of this
movement is that it started in a linea-
ment "gap" where there are no lineament
features and little topographic evidence
of faulting (Figure 50).
The Cleveland Hill Fault can be traced
on the ground and in exploration trenches
to within 2.3 km (1.4 mi) of the Bidwell
Canyon Saddle Dam. The Swain Ravine
Lineament fault zone continues to the
north and extends into Bidwell Canyon.
Hypocenters of aftershocks extend 10 km
(6 mi) north of the surface faulting and
pass beneath Oroville Dam at a depth of
about 5 km (3 mi) (Lahr and others, 1976),
Surface investigations, trenching, and
geophysical investigation failed to
/
Surface evidence of Cenozoic faulting is
rare. This is attributed to small dis-
placements at sufficiently long recur-
rence intervals to allow erosion to re-
move evidence of fault movements. More-
over, much of the study area is not
covered by Cenozoic deposits, making
determination of younger fault movements
difficult.
Within the area of detailed mapping, the
Swain Ravine, Prairie Creek and Paynes
Peak Lineaments were determined to be
Mesozoic fault zones. North of the de-
tail map area several lineaments are
apparant on high-altitude infrared and
.low-altitude black-and-white photographs.
For this study the major northern linea-
ments are informally named the Chico,
Soda Springs, Web Hollow and Paradise-
Magalia Lineaments. These lineaments
were field checked to determine if they
are faults. Figure 16 shows these linea-
ments and associated faults.
•/
r-f
Figure 50. Aerial northwest view of the
Cleveland Hill Fault along the western
side of Cleveland Hill. Note that
topographic expression for the fault
is lacking.
71
reveal faulting beyond an olive grove
south of Mt. Ida Road, about 2.3 km
(1.4 mi) south of Bidwell Canyon Saddle
Dam. However, the Swain Ravine Lineament
fault zone appears to go northward into
Bidwell Canyon. Faulting in the west
end of Bidwell Canyon Saddle Dam foun-
dation and a fault exposed in a water
tunnel about 1 km (0.6 mi) west of the
dam may be parts of a complex system of
faults in the Swain Ravine Lineament
fault zone. It can be conjectured that
the fault system consists of a band of
discontinuous, relatively short, small
faults along which displacement could
jump from fault to fault within the main
zone. This kind of fault discontinuity
could explain the inability to trace the
Cleveland Hill Fault continuously far-
ther north to link up with the faulting
at Bidwell Canyon Saddle Dam. The west-
ward tilt indicated by leveling surveys
on the saddle dam further suggests that
the fault system goes into the Bidwell
Canyon arm of the reservoir.
North of Lake Oroville a lineament con-
tinues on through Canyon Creek, along
the projected northerly trend of the
Swain Ravine Lineament fault zone
(Figure 16). However, geologic investi-
gation failed to reveal faulting along
the lineament. The markedly straight.
North Fork of Lake Oroville also is sug-
gestive of faulting, but no faulting
could be found along the north side of
the lake . Because the Swain Ravine
Lineament fault zone is a strong feature
of some size, it seems the zone should
continue through the reservoir. However,
field investigations did not prove this
to be true. Therefore it is assumed the
fault zone terminates in the reservoir.
The fault movement along the Cleveland
Hill Fault in the Swain Ravine Lineament
system prompted a number of exploration
trenches. These were mostly along the
faulted portion, but some were on other
parts of the Swain Ravine Lineament and
also on the nearby Paynes Peak and
Prairie Creek Lineaments. Trenching was
done by Department of Water Resouces,
U. S. Army Corps of Engineers, and by
72
Woodward-Clyde Consultants for'various
clients. Purpose of the trenching was
to investigate the nature of the faultin
in the underlying bedrock and to deter-
mine if previous Quaternary fault move-
ment could be detected in soil profile
overlying the bedrock. Although expo-
sures of faults in the bedrock were
usually obvious and easy to interpret,
the exposures of the overlying soil pro-
file were not so clear cut. Interpreta-
tion of earlier^ fault displacements seen
in the soil profiles were not necessaril
concurred with by all that saw the expo-
sures in the various trenches. For the
purposes of this study we have accepted,
without necessarily endorsing, the inter
pretations made in trenches by others.
For displacements of small magnitude,
such as along the Cleveland Hill Fault,
displacement of the soil profile in
trenches is difficult to detect. We are
not aware of any trench where such dis-
placement from the August 1, 1975, earth
quake could be detected, even though i
the trenches were excavated across the ,
ground cracking. The cracking could
usually be seen at least part way throug
the soil profile and sometimes, clear
through the usually shallow soil profile
to bedrock. Although offset of features
interpreted to be caused by earlier
fault movements could be seen in one
trench, other trenches nearby on the
same fault might not show offsets, or
show displacement of a different magni-
tude. In short, trenching does not
detect all of the previous fault move-
ments with great clarity — instead very
subtle features, subject to varying
interpretation, are usually revealed.
Earlier small fault movements can easily
pass undetected.
Of the 17 Department of Water Resources
trenches, 15 were on the Swain Ravine
Lineament fault zone. Eight of those
trenches (A, B, D, 5, 8, 12, 13 and 16)
were excavated across Cleveland Hill
Fault ruptures, and each of these ex-
posed a fault in bedrock beneath the
ground rupture. Two other trenches (7A
and 17) exposed bedrock faults, and the
remaining five trenches on the Swain
Ravine Lineament fault zone did not ex-
pose any faults.
Only one Department of Water Resources
trench exposed convincing evidence of
Quaternary movement on the Cleveland
Hill Fault prior to the 1975 event.
Trench DWR 8, across the Cleveland Hill
faulting, exposed a contact between two
alluvial units, at a depth of 3.3 m
(10.8 ft), with about 30 mm (1.2 in) of
apparent down-to-the-west vertical off-
set on the fault. Soil features near
the ground surface were not displaced,
indicating movement occurred prior to
the 1975 Oroville event. In their
Cleveland Hill No. 1 trench, Woodward-
Clyde Consultants report 46 cm (18 in)
of apparent vertical offset which they
interpret as having occurred in at least
three, and perhaps more, separate events.
This suggests that a 15 cm (6 in) move-
ment would be the maximum displacement
expected.
Forty-two exploration trenches were ex-
cavated by various investigators on the
Swain Ravine Lineament fault zone between
Bangor and Lake Oroville (Figure 47
and Table 1) . Many of these trenches
exposed west-dipping faults showing evi-
dence of multiple, small-scale (less
than 1 m) , normal Cenozoic movements.
An exception to this occurs in the U. S.
Bureau of Reclamation Orange Road
trenches, where some faults were found
to dip east, and one of these showed a
4.3 m (14 ft) normal offset. Five
trenches on the lineament just north of
the Yuba River, by the Corps of Engineers
(1977) exposed Mesozoic faults with no
Cenozoic movement.
Ages of movement on the Cleveland Hill
Fault and at other places along the
Swain Ravine Lineament fault zone are
based on displaced soil horizons. The
most prominent soil marker is a buried
paleosol. Gene Begg (person, commun.,
1977) and Roy Shlemon (person, commun.,
1977) estimate the paleosol to be at
least 100,000 years old, and soils
overlying it are 50,000 to 70,000 years
old. Similar paleosols in the Sierran
foothills have also been estimated to
be at least 100,000 years old by Swan
and Hanson (1977, 1978). The U.S. Geo-
logical Survey (1978, p. 43) has stated
that soils overlying the paleosol may
be younger - 10,000 to 25,000 years
old - and that a fault which displaces
the paleosol and not the overlying soil
should be considered to be a minimum of
10,000 years old. In summary, the part
of the Cenozoic record available, the
soil cover, indicates previous small
fault movements within the last 10,000
to 100,000 years.
Where older soil horizons are offset
more than successively younger ones, it
is interpreted that the fault has moved
several times during development of the
soil profile. The amount of displace-
ments seen, and the lack of surface fault
features along the Cleveland Hill Fault
suggest that small movements at relative-
ly long recurrence intervals have occur-
red over the past 100,000 years.
An east-west channel deposit of late
Cenozoic gravel crosses the Pajmes Peak
and Swain Ravine Lineaments northwest of
Bangor (Plate 1) , yet shows no field
evidence of fault displacement. More-
over, a small diorite plug across the
Swain Ravine Lineament in the same area
is not displaced, indicating it has not
been offset since emplacement, about
130 million years ago.
The fact that fault displacements are
seen in soils exposed by trenching, yet
no field evidence can be seen for larger
displacements of the late Cenozoic
gravel channel deposits or pluton, sug-
gests long-term cumulative displacement
is too small to detect by normal field
techniques. The apparently unbroken
pluton in the Swain Ravine Lineament
fault zone suggests undetectable dis-
placement for about 130 million years.
The same pluton relationship is seen
on the Prairie Creek Lineament fault
zone which is apparently truncated by
the Rocklin pluton.
73
The evidence indicates a pattern of
activity during the last 100,000 years
of small, infrequent, vertical fault
movements, along the Swain Ravine
Lineament fault zone. Presumably, such
displacements were produced by earth-
quakes of about the same magnitude as the
1975 Oroville earthquake. The average
slip rate during the last 100,000 years
may be faster than during most of the
last 130 million years, otherwise the
older rocks would be noticeably dis-
placed. For example, cumulative fault
displacement of 0.46 m (1.5 ft) in soil
was interpreted from relationships in
the Cleveland Hill No. 1 trench by
Woodward-Clyde Consultants. This gives
a maximum slip rate in the Cleveland
Hill area of 0.46 m (1.5 ft) per
100,000 years. Assuming the late
Cenozoic gravels overlying the Swain
Ravine Lineament fault zone are early
Quaternary, or about two-million years
old, then they should be offset about
9 m (30 ft) if the same slip rate pre-
vailed — a displacement large enough to
be noticed in the field. Applying the
same slip rate to the 130 million year-
old pluton would produce an offset of
about 600 m (1,960 ft).
The Swain Ravine Lineament fault is
the only one along which evidence of
Quaternary fault displacements was
found. However, these kind of fault
displacements are subtle and difficult
to detect, so it is possible, though
not proven, that similar levels of fault
activity have taken place along the
Prairie Creek and Paynes Peak Lineament
faults. South of the study area, the
Swain Ravine Lineament fault merges with
the Prairie Creek Lineament fault to
form one system (Figure 47) . Trenches
just south of where the two lineaments
merge revealed what is interpreted to
be Quaternary fault movements (Alt and
others, 1977). The persistent evidence
of Quaternary movements along the Swain
Ravine and the merged Swain Ravine-
Prairie Creek Lineament fault zones
suggests this may be a preferred avenue
along which small Quaternary fault move-
ments occur.
74
Prairie Creek Lineament Fault Zone;
Several areas of localized ground crack-
ing occurred during the Oroville earth-
quake and form a crude alingment that ex-
tends northwestward from the north end
of the Prairie Creek Lineament for 10 km
(6 mi) to Oroville. Further to the
northwest, Lovejoy basalt on the
Campbell and Sorensen Hills is discon-
tinuous with basalt on North and South
Table Mountains along a projection of
the lineament. This trend, projected
still further to the northwest, could
coincide with faulting in Tuscan
Formation along the Chico monocline.
Evidence is lacking, however, these
features may result from Cenozoic move-
ment along an underlying Mesozoic bed-
rock fault.
Even though no evidence of Quaternary
fault activity was seen along the
Prairie Creek Lineament fault zone, the
fact that Quaternary faulting has occur-
red just south of where it merges with
the Swain Ravine Lineament fault zone
suggests Quaternary activity has, or
could, take place along the Prairie
Creek zone. This possibility is rein-
forced by the occurrence of some small
earthquakes along the lineament, and the
yet unexplained system of cracks, the
"Palermo crack zone", that developed
along the northwest projection of the
Prairie Creek Lineament fault zone dur-
ing the Oroville earthquake. For these
reasons, the Prairie Creek Lineament
fault zone should be regarded as capa-
ble of the same kind of activity seen
along the Swain Ravine Lineament fault
zone. If the Prairie Creek Lineament
fault zone does continue northward as
an old Mesozoic fault zone more or less
concealed by younger rocks of the Super-
jacent Series, it would be the longest
of the lineament fault zones.
Paynes Peak Lineament Fault Zone; Of
the three lineament fault zones in the
Oroville area, Paynes Peak is the only
one along which no evidence or suggestion
of Quaternary activity is seen. Conse-
quently, it is assumed fault activity is
not as likely to occur along the Paynes
Peak Lineament as along the other two
zones.
tion exposed on South and North Table
Mountains, about 6 km (3.8 mi) to the
northeast along projection of strike.
Thermalito Powerplant Foundation Faults;
During construction, faults were exposed
in the foundation excavation for
Thermalito Powerplant. The zone consists
of several interlaced faults striking
from N30-44E, dipping steeply from 70NW
to 80SE, and offsetting Miocene age
Love joy Formation. The fault does not
offset overlying gravels of late Cenozoic
age. Apparent offsets are both normal
and reverse, and apparent cumulative
displacement across the zone is as much
as 12 m (40 ft), with the southeast
side moved downward relative to the
northwest side. No evidence for this
fault was observed in Love joy Forma-
Chico Lineament; The Chico Lineament
coincides with the upper hinge of the
Chico monocline (Figure 51) . A zone of
tensional faults, generally small, lies
along this hinge line in the area of
the lineament. These faults cut Upper
Pliocene Tuscan Formation.
A comprehensive study of faulting along
the Chico monocline was done by Burnett
(1965) . Additional studies dealing
with faults in Tuscan rocks are by
Creely (1965) and Burnett and others
(1969); field investigations were also
carried out for this report.
■•^#''^,:.'?5f-'?^-!^"-, ••
•^rgfm^
M^ _*.v%5«-
^f^. >•* ■
'■»y". -rf-ji^tnt i*ii III
^
■m^!^
Figure 51. Aerial northwest view of the Chico monocline that is locally developed in
Tuscan Formation. Note pattern of northwest-trending linear fractures defined by
dark vegetation lines. Location is northeast of Chico.
75
Figure 52. Normal fault (attitude: N3W, 62NE) in Tuscan Formation exhibiting 30 cm
(1 ft) of down-to-the-east displacement. Location is a roadcut exposure along Clark
Road approximately 6 km (3-7 mi) south of Paradise.
~~^»^ft^^.
Figure 53. Normal fault (attitude N6W, 65SW) in Tuscan Formation exhibiting 70
cm (2.2 ft) of down-to-the west displacement. Location is a roadcut exposure
along Clark Road about 6 km (3.7 mi) south of Paradise.
76
Faults in Tuscan rocks trend north-
northwest and dip either east or west .
These are normal faults which usually
have little vertical displacement
(Figures 52 and 53) . Displacements are
generally less than 1 m (3 ft); however,
displacements of 18 m (60 ft) (Burnett,
1965) and 31 m (100 ft) (Dave Harwood,
person, commun., 1978) have been reported.
Soda Springs Lineament; The Soda
Springs Lineament is about 16 km (10 mi)
long and is composed of linear topogra-
phic features and an area of springs.
Field investigation along the lineament
produced no evidence of faulting. Expo-
sures of Tuscan rock along Ditch Creek
(Sect. 9, T26N, R3E) are continuous
across the lineament and provide good
evidence against faulting. The springs
are interpreted to be interflow seeps
in the underlying, horizontally-bedded
Tuscan Formation.
Web Hollow Lineament: The Web Hollow
Lineament is a strong north-south trend-
ing feature at least 31 km (19 mi) long
and has been suggested to be a fault
(Quintin Aune, unpub. data; Alt and
others, 1977). A field check of fault
features described by Aune was made by
Department of Water Resources geologists
prior to this study; none of these fea-
tures could be attributed to faulting
(Mark McQuilkin, person, commun., 1977).
During this study the entire Web Hollow
Lineament was field checked and de-
termined not to be a fault.
A zone of very strong lineaments, paral-
lel to, and just east of the northern
end of the Web Hollow Lineament, can be
seen in the Tuscan Formation on low-
altitude photographs (Figure 54). These
cut across the topography in a northwest
trend. A check of these lineaments on
the ground failed to substantiate the
presence of faulting, however, photo-
graphic features so strongly suggest
fault control that they are interpreted
to be faults. The lack of surficial
fault features in the Tuscan Formation
suggests these are Upper Pliocene or
Pleistocene in age.
Paradise-Magalia Lineament; The
Paradise-Magalia Lineament is about
43 km (27 mi) long and trends north from
Oroville to Magalia (Figure 16). Linear
elements include a section of the
Feather River at Oroville, the east edge
of South Table Mountain, a drainage on
North Table Mountain and a linear ridge
on the west side of Magalia Reservoir.
whl^^m '^tw"
-^ 'IRON
' Nipyi^TftlN
Figure 5^. Vertical aerial view of fracture
zone developed in Tuscan Formation near
Iron Mountain on Deer Creek. Fractures
appear as dark vegetation lines which
transect topography.
77
o
o
oca
OJO
o
oi
in
Rock
VS
ft^v^\^^'^■^
\:>\\^
Figure 55. Map with cross section oriented perpendicularly to suspected fault
through Magi ia Reservoir.
78
This lineament was investigated through-
out most of its length on the ground.
Cenozoic fault features could only be
found where it contacts Love joy Forma-
tion on the south side of North Table
Mountain. Here a small fault, less
than 0.5 km (0.3 mi) long, cuts Lower
Pliocene basalt. Another fault of the
same size and attitude occurs just to
the west — off the lineament. Poor
exposures preclude determining a sense
of displacement of either fault, and
it is possible that rather than faults
they are unusually prominent cooling
joints .
Old mining reports indicate faults occur
in several mines along the Paradise-
Magalia Lineament northwest of Magalia.
A report by the California Department
of Natural Resources (1930) cites dis-
placements of up to 70 m (225 ft) in
Tertiary channel deposits below Tuscan
Formation. These faults do not cut
overlying Tuscan Formation and must be
pre-Pleistocene in age. Faults in the
mines as well as a Mesozoic fault at
Magalia Reservoir trend more westerly
than the Paradise-Magalia Lineament and
may not be related to it.
Alt and others (1977, pp. 14-21) state
that a prominent Cenozoic fault scarp
occurs in Tuscan rocks along the Paradise-
Magalia Lineament on the west side of
Magalia Reservoir. Detailed mapping of
the Tuscan-basement rock contact during
this investigation showed no evidence
of faulting. A cross-section based on
this mapping, drawn perpendicular to
this scarp, shows no displacement of the
base of the Tuscan Formation (Figure 55) .
Summary ; Cenozoic fault movements have
occurred in the Oroville area on both
pre-existing Mesozoic bedrock faults,
such as the Cleveland Hill Fault, and on
faults in Cenozoic rocks, such as those
in the Tuscan and Love joy Formations.
It is possible that the faults cutting
Cenozoic rocks may also be along Mesozoic
faults in bedrock concealed by the over-
lying younger formations.
Potential for future earthquakes and
ground rupture in the Oroville area is
considered to be greatest on the Swain
Ravine Lineament fault zone, to the north
and the south of that portion of fault
that ruptured in the 1975 event.
The fault responsible for the magni-
tude 5.7 earthquake that occurred north-
east of Chico, California, in 1940, was
not found.
Mesozoic Folds
Smartville ophiolite in the Bangor
quadrangle and melange in the Cherokee
and Berry Creek quandrangles are iso-
clinally folded. Exposures of relict
pillows provide structural control for
tops of section. Near Bangor, pillowed
sequences dip east and are inverted;
north of this location, pillowed rocks
are right-side-up and dip east. Tops
of these sections are oriented in oppo-
site directions and suggest that large-
scale folding deforms the ophiolite.
Large-scale folding is locally confirmed
by concordant small-scale folds inter-
preted to be parasitic deformation.
Mesozoic folds trend north-northwest
and plunge south at angles less than
35 degrees. Plunge directions conform
with orientations described in several
geologic studies of the foothills
(Bateman and others, 1963; Clark, 1964,
1976; Creely, 1965; Hietanen, 1973a;
Duf field and Sharp, 1975). Axial planes
of these folds, oriented subconcordant
to metamorphic foliation, dip steeply
east or are vertical. Localized folds
occur in metamorphosed country rock
adjacent to Sierran plutons (Compton,
1955; Clark, 1964; Hietanen, 1973a).
Cenozoic Folding
Cenozoic folding does not affect study
area rocks but is described at several
locations in the nearby area. At Tuscan
Springs, approximately 8 km (5 mi) north-
east of Red Bluff, the Tuscan and Chico
Formations are gently deformed into
open folds (Anderson, 1933). Addition-
ally, Hudson (1951, 1955) has described
folded Superjacent Series rocks in the
Mount Lincoln-Castle Peak area.
79
The Chico monocline, as described by
Bryan (1923), Anderson (1933), Burnett
(1965) and Burnett and others (1969),
trends approximately N30W and forms the
24 km (15 mi) straight eastern boundary
of the Great Valley between Chico and
Red Bluff (Figure 51) . The monocline
steepens Tuscan Formation dips from
2 degrees east of the fold, to 8 to
10 degrees within the hinge area
(Burnett and others, 1969). This is the
best developed Cenozoic fold in the
immediate area.
Most Cenozoic folding occurred prior
to deposition of the Pleistocene (?)
Red Bluff Formation as these unconform-
able gravels are not deformed (Anderson,
1933). The Red Bluff Formation and late
Cenozoic gravels in the study area are
incised by actively-downcutting drainages
which indicate the foothill region is
experiencing uplift; some deformation
must be associated with this uplift.
SUMMARY OF GEOLOGIC HISTORY
The geologic history and tectonic
movement in the Oroville area is summar-
ized in chronologic order of occurrence.
The timing of events is substantiated
by field data or referenced from inves-
tigators who did particular studies con-
cerning aspects of the geologic history.
Absolute dates for events are used if
available; relative time, based upon
fossils, is used where radiometric dates
are lacking.
Table 2
Summary of Geologic Events
Event
Date
Cenozoic Time
Oroville earthquake - small
fault movement near Cleveland
Hill along Swain Ravine
Lineament fault zone
1975
2. Development of "A" and "B"
soil profiles. Some small
fault movements along Swain
Ravine and merged Swain
Ravine-Prairie Creek fault
zones
10,000-25,000 years before present
(uses, 1978)
50,000-70,000 years before present
(Gene Begg and Roy Shlemon, person,
commun. , 1978)
Development of "Paleo B" soil
profiles; small fault
movements.
4. Alluvium deposited
5. Development of late Cenozoic
faulting in the foothill belt
6. Older gravels deposited
100,000 years before present
(Gene Begg and Roy Shlemon,
person, commun., 1978)
140,000 years old (USGS, 1978)
Pleistocene - Recent
Post-Pliocene (Alt and
others, 1977)
Pliocene-Pleistocene (?)
80
Event
Date
10.
Tuscan Formation deposition
began
Sierran uplift and westerly
tilting began
Love joy Formation, basalt
flows from eastern source
Oroville tuffs (Mehrten
Formation-?) deposited
Pliocene, 3.3 million years
(Lydon, 1968)
Pliocene, 4-10 million years
(Christensen, 1966; Wright, 1976;
Hay, 1976)
22.2 to 23.8 million years
(Dalrymple, 1964)
23.8 million years
(Dalrymple, 1964)
11.
Auriferous gravels deposited
12. lone Formation deposited
Upper Eocene - Lower Oligocene
(Durrel, 1966)
Middle Eocene (Creely, 1965) to
early Oligocene
13. Early Sierran uplifts
Cretaceous-early Tertiary
Mesozoic Time
Chico Formation deposited
Upper Cretaceous (Taff and others,
1940; Creely, 1965)
Plutonism (Yosemite intrusive
epoch) - intrusion is respon-
sible for thermally metamor-
phosing country rocks in the
study area
126-138 million years (Gromme and
others, 1970; Evemden and
Kistler, 1970)
Mesozoic faults (Foothills
Fault System) - formed by
collision of arc and ophio-
lite with continent
Middle Kimmeridgian to late
Tithonian
4. Smartville ophiolite formed
5. Monte de Oro Formation
deposited
6. Arc Rocks extruded
7. Melange formed
Oxfordian to Kimmeridgian
Late Oxfordian to early
Kimmeridgian (Imlay, 1961)
Oxfordian (?) to early
Kimmeridgian (Creely, 1965)
Middle to Upper Jurassic
(Kimmeridgian, Bob Treet,
person, commun., 1978)
81
i
The above tabulation of events indi-
cates tectonic activity is spasmodic.
Major activity was in Mesozoic time.
The Sierran uplift is a major regional
event, but the main influence on rocks
of the western foothill belt around
Oroville is to tilt Cretaceous and
younger rocks gently to the west. Vol-
canic activity about 22-24 million years
ago deposited basalt flows (Lovejoy
Formation) , lahars and water lain vol-
caniclastic rocks of the Oroville tuff.
In early Pleistocene time, fault move-
ments began again in response to the
most recent Sierran uplift, mostly along
the old Mesozoic faults. Some younger
rocks, mainly Tuscan Formation, also are
faulted. In the Oroville study area,
Cenozoic fault displacements are general-
ly small. Elsewhere, Cenozoic displace-
ments up to 197+ m (600 ft) are reported
(Alt and others, 1977).
The last 100,000 years has been a
period during which small fault displace-
ments on the order of centimetres occur-
red at infrequent intervals along the
older Mesozoic fault zones.
CAUSES OF THE OROVILLE EARTHQUAKE
Geologic investigations reveal that the
Oroville earthquake is not unique in
the seismic history of the northwestern
Sierra Nevada foothill belt. The 1940
magnitude 5.7 earthquake north of what
is now Lake Oroville demonstrated that
the region is capable of generating
moderate-magnitude earthquakes. The
trenching and other exploratory work
revealed evidence for small displace-
ments in soil during the last
100,000 years or less, depending upon
which interpretation is accepted for
the age of soils displaced by faulting.
Presumably these small fault movements
also were accompanied by earthquakes
similar to the 1940 and 1975 magnitude
5.7 earthquakes that occurred in the
Oroville region.
The geologic investigations of the
Oroville area revealed old fault zones
in bedrock. These old fault zones formed
during Mesozoic time — subduction at a
plate boundary is postulated as the geo-
logic model for genesis of the faults.
Actually, the geologic model assumed for
formation of the old fault system is not
as critical as the fact that these older
fault zones formed in a different tec-
tonic regime than exists today. The im-
print of earlier tectonism has left zones
of weakness along which fault movements
caused by the current Cenozoic tensional
regime tend to occur.
t
The present tectonic pattern clearly
seems to be one of general east-west
extension. The behavior of the
Cleveland Hill Fault, the opening of the
fault cracks with time and the geodetic
work in the Oroville area, all suggest
normal fault movements resulting from
east-west tension. A fault plane solu-
tion of the August 1975, Oroville earth-
quake series indicates normal dip-slip
movement (Langston and Butler, 1976;
Lester and others 1975), also indicating
east-west tension.
Recent leveling work done by Bennett and
others (1977) suggests the Sierran block
is still undergoing uplift. This uplift
is postulated to be the cause of tension
in the western foothills. Bennett (1978)
continued examination of leveling data
and was able to demonstrate noticeable
changes in elevation across both the
Bear Movintains and Melones Fault zones,
again indicating crustal movements pre-
fer to occur along the old fault zones.
In summary, for at least the past 4 mil-
lion years the foothill region probably
has been in east-west tension. It can
be speculated that this tension reduced
frictional stresses along north-trending
older fault systems, allowing small grav-
itational adjustments and fault movements.
These movements probably were accompanied
by earthquakes comparable to the 1940 and
1975 magnitude 5.7 earthquakes that oc-
curred in the Oroville area. These fault
movements commonly occur along the small-
er individual faults within the older
fault zone complexes. Possibly not all
82
movements occur along existing faults,
but displacements revealed thus far sug-
gest that most do.
Reservoir-Induced Seismicity
Reservoir-induced seismicity has been
greatly studied in the last few decades.
Several researchers (for example, Gupta
and others, 1973; Rothe", 1973; Bozovic,
1974) note the following characteristics
of reservoir induced seismicity:
1. Earthquake activity begins soon after
initial impoundment.
2. Large numbers of foreshocks occur
over an extended time period before
the main shock.
3. Time versus frequency plots of fore-
shocks and aftershocks differ from
patterns of tectonically induced
seismicity.
4. Reservoir-induced earthquakes are
shallow focus.
5. Proximity of reservoir-induced seis-
micity to the triggering dam or res-
ervoir is usual.
6. Relatively high "b" values for fore-
shocks of reservoir-induced seismic
events as established by the equation
log N = a-bM where "b", the slope of
the curve, is related to the propor-
tion of large-to-small earthquakes,
"N" is the cumulative frequency of
magnitude "M" earthquakes, and "a"
is a constant determined by area
where data were gathered, time dura-
tion and areal seismicity.
7. A high ratio of the strongest magni-
tude aftershock to the magnitude of
the main seismic event.
The most consistent characteristic of
reservoir- induced seismic activity is
the onset of the earthquakes soon after
initial impoundment begins (Rothe, 1973).
Some examples (after Packer and others,
1977, Appendix A) are listed below.
Reservoir
Koyna
Hsinfengkiang
Hendrik Verwoed
Boulder
Contra
Grandval
Elapsed time from
beginning impoundment
to start of seismicity
Immediately
1 mo.
6 mo.
9 mo.
10 mo.
15 mo.
In comparison, seismic activity at
Oroville occurred more than eight years
after water impoundment began.
A second characteristic of reservoir-
induced seismicity is that a large num-
ber of foreshocks occur over a longer
period of time than would be expected
for tectonically-induced seismic events
(Rothe, 1973; Bozovic, 1974). For ex-
ample Kremasta Reservoir had 17 fore-
shocks in 30 days. Koyna Reservoir
had 90 foreshocks in 19 days, and
Kariba Reservoir had 20 foreshocks in
one day (Gupta and others, 1973). The J
frequency of foreshocks at Oroville,
21 events in 30 days prior to the main
shock, is similar to the Kremasta data.
Mogi (1963) discovered that the plot
of time versus frequency for reservoir-
induced foreshocks and aftershocks dif-
fered from the pattern for tectonically-
induced earthquakes. The reservoir-
induced seismic pattern (Type II)
includes a greater foreshock buildup and
a longer period of aftershocks.
Figure 56 shows Mogi's "Type II"
(reservoir-induced) seismic pattern
compared with the pattern of the Oroville
earthquake series .
Shallow focal depths for reservoir-
induced earthquakes are also a common
characteristic (Bozovic, 1974). Some
examples of this characteristic are
Monteynard Reservoir, 0.0 km (0.0 mi);
Hendrik Verwoed Reservoir, 6 km
(3.7 mi); Boulder Reservoir, 1.5 to
9 km (0.9 to 5.6 mi). The main shock
of the Oroville series had a depth of
8.8 km (5.5 mi) and aftershock depths
from 1.3 to 10.4 km (0.8 to 6.5 mi)
(Akers and others, 1977).
83
FORESHOCKS
TIME
MOGl'S "type n" PATTERN
11
F'M'4 'm'j'j
1975
Time (6/28/75 to 4/30/76)
PATTERN FOR THE OROVILLE SERIES
u
Figure 56. Comparison of foreshock-af tershock patterns for the Oroville earthquake
and Mogi's "Type M" (reservoi r- i nduced) earthquakes.
A
r\
\/\
JV
A
A
n
r^
r"
\
/
\
~\
1
Vj
j
4
1
1
1
1
1
1967 19(8
1976 1977 1979
Figure 57. Water level history of Lake Oroville from initial filling to September
1978
84
In most reservoir-induced seismic
events the foci of the earthquakes are
very close to, or directly under, the
reservoir or dam. This characteristic
is noted for earthquakes at Boulder,
Monteynard, Grandval, Oued Fodda,
Kariba, Kremasta, Marathon and Koyna
reservoirs. The most distant earthquake
was within 10 km (6.2 mi) of the Koyna
Reservoir dam (Gupta and others, 1973).
The main shock of the Oroville earth-
quake series was more distant, approxi-
mately 12 km (7.5 mi) from Oroville Dam.
Relatively high "b" values for fore-
shocks and aftershocks of reservoir-
induced events are common (Gupta and
others, 1973). A comparison of "b"
values for accepted cases of reservoir-
induced seismicity with those of the
Oroville earthquake shows a significant
difference. Note "b" value comparisons
below (after Morison and others, 1976).
"b" Values
Reservoir
Foreshocks
Aftershocks
Kariba
1.1
1.0
Kremasta
1.4
1.1
Koyna
1.9
1.3
Oroville
0.37
0.61
of 100 m (328 ft) in February 1968, and
has never been lowered beneath that
level. A plot of post-construction res-
ervoir elevations with the date of the
August 1, 1975, earthquake is shown in
Figure 57. The 1975 change from low
water in January to high water in late
May represents an increase of 29 percent
in 5 months; initial reservoir filling
during the same time period in 1968
generated an increase in storage of
44 percent with no resulting seismicity.
In comparing data from the Oroville
earthquake with reported data from known
reservoir-induced earthquakes, the
Oroville event has some, but not all, of
the characteristics attributed to
reservoir-induced earthquakes. The long
elapsed time between reservoir filling
and the Oroville earthquake is a signi-
ficant departure from what has occurred
in generally accepted cases of reservoir-
induced seismicity. The epicentral dis-
tance from the reservoir is slightly
large and the "b" values are signifi-
cantly too small. A comparison of ac-
cepted characteristics of reservoir-
induced earthquakes with those of the
Oroville earthquake, does not show whe-
ther or not Lake Oroville caused the
earthquake series.
Another feature common to reservoir-
induced seismicity is a high ratio,
typically 0.8 to 0.9 (Gupta and others,
1973), of the strongest aftershock mag-
nitude to the magnitude of the main
shock. The ratio for the Oroville
series is 0.91.
A relationship has been postulated
between rate of reservoir loading,
water depth and induced seismicity
(Rothe, 1969). Induced earthquakes
seem to be more commonly associated
with reservoirs whose water depths are
100 m (328 feet) or greater and during
periods of rapid loading (generally
the first reservoir filling) ; large
water level fluctuations also induce
seismicity (Carder, 1945). Lake
Oroville^ approximately 200 m (656 ft)
deep at maximum pool, reached a depth
The picture is further clouded by the
background seismicity which indicates an
earthquake comparable to the 1975
Oroville earthquake occurred before the
reservoir existed. Small fault displace-
ments in soil profiles exposed by trench-
ing suggest Oroville type events have
been occurring for the past 100,000
years. In short, the Oroville earth-
quake is compatible with the regional
pattern of seismicity and, therefore,
need not be related to Lake Oroville
at all.
The mechanisms customarily used to
explain reservoir-induced earthquakes
are (1) increase in stress caused by
weight of water in the reservoir and
(2) increase in pore pressure resulting
from the increase in hydrostatic head
imposed by the reservoir. The increase
85
in pore pressure mechanism is more favor-
ed. Both theories assume stress condi-
tions in the hypocentral area are in
such delicate balance that only small
incremental changes in stress will trig-
ger an earthquake.
The epicenter of the August 1, 1975,
Oroville earthquake was 12 km (7.5 mi)
from Lake Oroville. Although no computa-
tions were made by the Department to
estimate how much Lake Oroville changes
stress in the hypocentral area, at that
distance and depth change in stress
should be very small.
A reconnaissance survey of springs
and wells in the area indicates ground
water levels in the foothill area to the
east and north of the epicentral area
are generally higher than water in Lake
Oroville. Assuming hydrostatic pressures
in the hypocentral area are controlled
by ground water levels, the addition of
Lake Oroville in such a hydrostatic
regime probably would have no affect on
either pore pressure or degree of
saturation.
The evidence available does not indi-
cate a causal relationship between Lake
Oroville and the earthquake, but the
possibility cannot be eliminated conclu-
sively at this time.
POTENTIAL HAZARDS TO STATE
WATER FACILITIES
Because the August 1, 1975, Oroville
earthquake probably relieved much of the
regional strain, it seems unlikely that
a similar event will occur in the same
place in the near future. Therefore, the
next earthquake of comparable magnitude
probably would occur north or south of
the 1975 earthquake and its zone of
aftershocks. Despite the improbability
of another local earthquake, estimates
of hazards to facilities are based on the
assumption that a 1975 type earthquake
will happen again in the same area. In
other words, the most pessimistic or con-
servative view was taken.
Hazard posed by regional faults fall
into three general categories, (1) haz-
ards created by ground shaking, (2)
hazards created by fault displacement,
and (3) regional changes in ground
elevation.
Ground Shaking
Nothing was seen during the course of
geologic investigations that indicates
local earthquakes would exceed the mag- I
nitude 6.5 Reanalysis Earthquake recom-
mended by the Special Consulting Board
for the Oroville earthquake.
The intuitive conclusion to be drawn
from the geologic studies would be that
the magnitude 5.7 earthquake of August 1,
1975, is close to the strongest to be
expected and that the magnitude 6.5 local
earthquake assumed for reanalyses of
structures is very conservative. Geo-
logic studies suggest the Swain Ravine
or Prairie Creek Lineament fault zones
are the most likely source of future j
strong earthquakes.
Fault Displacement
Earthquakes of the size likely to
occur in the Oroville area may or may i
not cause surface rupture. If surface
fault displacement does occur it is most
likely along the Swain Ravine Lineament
fault zone or perhaps the Prairie Creek
Lineament fault zone. However, in the
east-west tensional environment which
apparently prevails in the Oroville area,
small displacement could occur along any
of the older faults or shear zones. Such i
an event along the minor faults is con-
sidered possible, but improbable.
Maximum displacements in the 1975
earthquake were about 50 mm (2 in) verti-
cal displacement and about 25 mm (1 in)
horizontal separation. In a somewhat
larger event, displacements might pos-
sibly be several times larger than these
values along north-south trending faults.
Although the displacements along the
86
Cleveland Hill Fault took considerable
time to reach a maximum in 1975, dis-
placements may not always develop so
slowly. Therefore, for purposes of
analyses, instant displacement should be
assumed. It appears that the only import-
ant structure which could be subjected
to such displacements on north-south
trending faults would be the Bidwell
Canyon Saddle Dam.
Regional Changes in Ground Elevation
Although regional changes in ground
elevation were measurable at Oroville,
the maximum change of 60 mm (2.5 in) is
not enough to pose a hazard to State
water facilities. It is not expected
this magnitude of elevation change would
be exceeded by any future earthquake.
Therefore, elevation changes are not
expected to pose a hazard to facilities.
Potential Hazard
to Specific Facilities
Oroville Dam and Saddle Dams
The Cleveland Hill Fault could not be
traced north of Mt. Ida Road about 2.1 km
(1.3 mi) south of Bidwell Canyon Saddle
Dam. However, the Swain Ravine Lineament
fault zone appears to go into the Bidwell
Canyon area of the reservoir. A fault
was mapped in the foundation of Bidwell
Canyon Saddle Dam near the right abut-
ment. It should be assumed this fault
is capable of the maximum displacement
cited under "Fault Displacement." Bid-
well Canyon Saddle Dam is the only struc-
ture at Oroville with this degree of
exposure to the probability of future
fault displacements.
Numerous faults were mapped in the
foundation of Oroville Dam. None of
these appear significant and do not
appear to be particularly related to the
major north-trending Mesozoic fault zones.
It is possible that some small displace-
ments could occur along the faults in
the dam foundation. It is considered
improbable that this would happen. This
aspect should be looked at as part of
the reanalysis of the main dam.
If the 60-degree westward dip of the
Cleveland Hill Fault is assumed to con-
tinue at the reservoir, then faulting in
the Swain Ravine Lineament fault zone
could dip under the dam, passing under-
neath the dam at a depth of about 5 km
(3 mi). It must be assumed that earth-
quakes can occur right under the dam.
However at such shallow depth, the
earthquakes would be of small magnitude.
Numerous landslides developed around
Lake Oroville since the reservoir has
been in operation and there is geologic
evidence for a large number of older
slides. When the steep slopes border-
ing the reservoir are heavily saturated
by winter rain, the area is landslide-
prone and a strong shake during such a
period could trigger landslides into
the reservoir. While such failure could
be dangerous to boaters on the lake, it
is not anticipated the dams would be
endangered due to the large amount of
freeboard which was provided on the
Oroville dams. This freeboard of 6.7 m
(22 ft) is expected to contain any waves
that might be generated by landslides.
Large seiches did not develop in the
reservoir during the 1975 earthquake,
but if they should, the high freeboard
is expected to contain seiche waves also.
Thermalito Forebay and Afterbay
Despite the absence of conclusive
evidence, it is possible the Prairie
Creek Lineament fault zone extends far-
ther northwest on a trend roughly paral-
leling Highway 70 between Thermalito
Power Canal and Wicks Corners. A
sequence of three earthquakes (magni-
tude 2.8-3.0) occurred just east of
this stretch of highway on December 12,
1976. Therefore, it should be assumed
that an earthquake comparable to the
1975 Oroville earthquake could occur
along the northwest projection of the
Prairie Creek Lineament fault zone near
the east end of Thermalito Forebay.
Fault displacements if they were to
occur, would probably be in the Power
Canal in a section excavated below natu-
ral ground and therefore would not pose
great hazard.
8—78786
87
Thermallto Powerplant
Cenozoic faults underlie Thermallto
Powerplant. As much as 12 m (40 ft)
of apparent vertical displacement occurs
along a system of faults that roughly
parallel the longitudinal axis of the
powerhouse. The Cenozoic fault activity
suggests small displacements could occur
again, particularly if a 1975 type earth-
quake were to occur along the Prairie
Creek Lineament fault zone. Such an
occurrence is viewed as a possible,
though improbable, event.
Other Structures
For the remainder of the Oroville
facilities the main hazard would be from
groimd shaking earthquakes might cause.
A number of structures have faults in
their foundations and, conceivably,
small displacements could occur along
these faults. It is considered improb-
able that displacements would occur, and
if they did, it does not seem the damage
would be significant. Structures with
faults in their foundations are listed
below:
Edward Hyatt Powerplant
Oroville Dam Spillway
Thermallto Diversion Dam
Thermallto Power Canal
Parish Camp Saddle Dam
SUMMARY AND CONCLUSIONS
1. The August 1, 1975, Oroville earth-
quake was accompanied by movement on
the previously unrecognized Cleveland
Hill Fault. A linear zone of discon-
tinuous ground cracking developed
along the fault about 7 km (4.3 mi)
east of the main shock epicenter.
2. Initial length of ground rupture on
the Cleveland Hill Fault was about
1.6 km (1.0 mi). Over a period of
about 12 months the ground cracking
extended progressively to the north,
reaching a total length of 8.5 km
(5.3 mi).
Offset along the fault was greatest
in the southern segment, where the
original cracking occurred. Offset
increased with time; movement
amounted to about 50 mm (2 in) verti-
cal displacement and 25 mm (1 in)
horizontal extension.
The Cleveland Hill Fault was not en-
countered by trenching or geophysical ,
investigation north of Mt . Ida Road. '
Aftershock hypocenters projected up
a calculated fault plane indicate the
fault at the ground surface trends
into Bidwell Canyon and that it may
pass beneath Oroville Dam at depth.
Trenching across the Cleveland Hill
Fault by Department of Water Resource;
and others provides evidence for
multiple small fault displacements
during the past 100,000 years. These
displacements would likely have pro-
duced earthquakes similar to the 1975
Oroville event.
Three major lineament-fault zones, thi
Paynes Peak, Swain Ravine, and PrairL
Creek, have been delineated in the
area by geologic studies. These
lineament-fault zones are complex
bands of discontinuous, intertwined,
steeply dipping faults which were
formed during Mesozoic or earlier
time under the influence of a differ-
ent tectonic stress regime than exists
today. The Cleveland Hill Fault is I
within the Swain Ravine Lineament
fault zone.
Most Cenozoic fault movements in the
Sierran foothill belt are caused by
east-west extensional stresses re-
activating pre-existing Paleozoic
and Mesozoic faults such as those
comprising the lineament-fault
zones.
Historic (Cenozoic) faulting and
historic earthquake records in the
foothill region demonstrate that the
current and long-range level of
seismic activity is one of low- to
moderate-magnitude earthquakes at
relatively long recurrence intervals.
88
occasionally resulting in minor
ground rupture and offset.
9. Nothing was seen in this geologic
study to indicate that earthquakes
greater than Richter Magnitude 6.5
should be expected in the Oroville
area.
10. Maximum offset that should be anti-
cipated from another Oroville-type
earthquake is estimated to be 50 mm
11.
(2 in) of vertical displacement and
25 mm (1 in) horizontal extension.
For a somewhat larger event dis-
placement might be several times
larger than these values along
north-south trending faults.
The evidence available does not
indicate a causal relationship
between Lake Oroville and the earth-
quake, but the possibility cannot be
eliminated conclusively at this time.
89
REFERENCES CITED
Akers, R. J., Marlette, J. W. , Morrison, P. W. , Jr., and
Struckmeyer , H. E., 1977, "Performance of the Oroville Dam
and Related Facilities During the August 1, 1975 Earthquake."
Dept. Water Resources Bull. 203, 102 p.
Allen, V. T., 1929, "The lone Formation of California." Univ.
Calif. Pub., Bull. Dept. Geol. Sci., v. 18, p. 347-448.
Allum, J. A. E., 1966, "Photogeology and Regional Mapping."
New York, Pergamon Press, 107 p.
Alt, J. N., Schwartz, D. P., and McCrumb, D. R., 1977, "Regional
Geology and Tectonics," _in Woodward-Clyde Consultants,
Earthquake Evaluation Studies of the Auburn Dam Area, v. 3,
118 p.
Anderson, C. A., 1933, "The Tuscan Formation of Northern California
with a Discussion Concerning the Origin of Volcanic Breccias."
Univ. Calif. Pub., Bull. Dept. Geol. Sci., v. 23, p. 215-276.
Bailey, E. H., Blake, M. C, Jr., and Jones, D. L., 1970, "On-land
Mesozoic Oceanic Crust in California Coast Ranges." U. S.
Geol. Survey Prof. Paper 700-C, p. 70-81.
Bailey, E. H. , Irwin, W. P., and Jones, D. L., 1964, "Franciscan
and Related Rocks, and Their Significance in the Geology of
Western California." Calif. Div. Mines and Geol. Bull. 183,
177 p.
Baird, A. K., 1962, "Superposed Deformations in the Central Sierra
Nevada Foothills East of the Mother Lode." Univ. Calif. Pubs.
Geol. Sci., v. 42, p. 1-69.
Bateman, P. C, and Clark, L. D., 1974, "Stratigraphic and Structural
Setting of the Sierra Nevada Batholith, California." Pacific
Geology, v. 8, p. 79-89.
Bateman, P. C, Clark, L. D., Huber, N. K., Moore, J. G. , and
Rinehart, C. D., 1963, "The Sierra Nevada Batholith - a
Synthesis of Recent Work Across the Central Part." U. S. Geol.
Survey Prof. Paper 414-D, p. 1-46.
Bateman, P. C, and Wahrhaftig, C, 1966, "Geology of the Sierra
Nevada," ±n_ Bailey, E. H. (ed.). Geology of Northern California.
Calif. Div. Mines and Geol. Bull. 190, p. 107-172.
Beck, J. L., 1976, "Weight-Induced Stresses and the Recent Seismicity
at Lake Oroville, California." Seis. Soc. America Bull.,
V. 66, n. 4, p. 1121-1131.
Becker, G. F., Turner, H. W. , and Lindgren, W. , 1898, "Bidwell Bar,
California." U. S. Geol. Survey Folio 43, scale 1:125,000.
90
Bennett, J. H. , Taylor, G. C, and Toppozada, T. R., 1977, "Crustal
Movement in the Northern Sierra Nevada." California Geology,
Calif. Div. Mines and Geol., p. 51-57.
Blake, M. C, Jr., and Jones, D. L., 1974, "Origin of Franciscan
Melanges in Northern California," _in Dott, R. H., Jr., and
Shaver, R. H. ( eds . ) , Modern and Ancient Geosynclinal
Sedimentation. Soc. Econ. Paleon. Mineral. Spec. Pub. 19
p. 345-357.
Bond, G. C, Menzies, M. , Moores, E. M., D'Allura, J., Buer, K.,
Day, D., Robinson, L. , and Xenophontos, C, 1977, "Paleozoic-
Mesozoic Rocks of the Northern Sierra Nevada: Field guide for
the Geol. Soc. America Cordilleran Section Meeting," Sacramento,
^ 38 p.
Bozovic, A., 1974, "Review and Appraisal of Case Histories Related
^ to Seismic Effects of Reservoir Impounding." Engineering
Geology, v. 8, p. 9-27.
Brewer, W. , 1930, "Up and Down California in 1860-1864," in. Farquhar,
F. P. (ed.). Journal . Yale Univ. Press, p. 339.
Bryan, K., 1923, "Geology and Ground Water Resources of Sacramento
Valley California." U. S. Geol. Survey Water Sup. Paper 495,
285 p.
Buer, K. Y., 1977, "Stratigraphy, Structure and Petrology of a
Portion of the Smartsville Complex, Northern Sierra Nevada,
California" (abs,): Geol. Soc. America Abstracts with Programs,
V. 9, p. 394.
1978, "Stratigraphy, Structure and Petrology of a Portion of
the Smartsville Ophiolite, Yuba County, California." MS thesis,
Univ. California Davis.
Burchfiel, B. C, and Davis, G. A., 1972, "Structural Framework and
Evolution of the Southern Part of the Cordilleran Orogen,
Western United States." Am. Jour. Sci., v. 272, p. 97-118.
1975, "Nature and controls of Cordilleran Orogenesis, Western
United States: Extensions of an Earlier Synthesis." Am. Jour.
Sci., V. 275-A, p. 363-396.
Burk, C. A., 1965, "Geology of the Alaskan Peninsula-Island Arc and
Continental Margin." Geol. Soc. America Mem. 99, 250 p.
Burnett, J. L., 1965, "Fracture Traces in the Tuscan Formation,
California." Calif. Div. Mines and Geol. Spec. Rept . 82,
p. 33-40.
Burnett, J. L., Ford, R. S., and Scott, R. G., 1969, "Geology of the
Richardson Springs Quadrangle, California." Calif. Div. Mines
and Geol., Map Sheet 13, scale 1:62,500.
91
Burnett, J. L., and Jennings, C. W. , 1962, Geologic Map of California,
Chico Sheet: Calif. Div. Mines and Geol . , scale 1:250,000.
Cady, J. W. , 1975, "Magnetic and Gravity Anomalies in the Great
Valley and Western Sierra Nevada Metamorphic Belt, California."
Geol. Soc. America Spec. Paper 168, 56 p.
California Department of Natural Resources, 1930, "Mining in
California." Calif. Div. Mines, v. 26, n. 4, p. 383-412.
Carder, D. S., 1945, "Seismic Investigations in the Boulder Dam Area,
1940-1944, and the Influence of Reservoir Loading on Local
Earthquake Activity." Seis. Soc. America Bull., v. 35,
p. 175-192.
Cebull, S. E., 1972, "Sense of Displacement Along Foothills Fault
System: New Evidence from the Melones Fault Zone, Western
Sierra Nevada, California." Geol. Soc. America Bull., v. 83,
p. 1185-1190.
Christensen, M. N. , 1966, "Late Cenozoic Crustal Movements in the
Sierra Nevada of California." Geol. Soc. America Bull., v. 77,
n. 2, p. 163-185.
Churkin, M. , Jr., 1974, "Paleozoic Marginal Ocean Basin-Volcanic Arc
Systems in the Cordilleran Foldbelt," j^ Dott, R. H., Jr., and
Shaver, R. H. (eds.). Modern and Ancient Geosynclinal
Sedimentation . Soc. Econ. Paleon. Mineral., Spec. Pub 19,
p. 174-192.
Clark, L. D., 1960, "Foothills Fault System, Western Sierra Nevada,
California." Geol. Soc. America Bull., v. 71, p. 483-496.
1964, "Stratigraphy and Structure of Part of the Western Sierra
Nevada Metamorphic Belt, California." U. S. Geol. Survey Prof.
Paper 410, 70 p.
1976, "Stratigraphy of the North Half of the Western Sierra
Nevada Metamorphic Belt, California." U. S. Geol. Survey
Prof. Paper 923, 26 p.
Clark, M. M. , Sharp, R. V., Castel, R. O., and Harsh, P. W., 1976,
"Surface Faulting near Lake Oroville, California in August
1975." Seis. Soc. America Bull., v. 66, n. 4, p. 1101-1110.
Coleman, R. G. , 1971, "Plate Tectonic Emplacement of Upper Mantle
Peridotites along Continental Edges." Jour. Geophys . Research,
V. 76, n. 5, p. 1212-1222.
1977, "Ophiolites . " New York, Springer-Verlag, 229 p.
Coleman, R. G. , and Irwin, W. P., 1974, "Ophiolites and Ancient
Continental Margins," Jji Burk, C. A., and Drake, C. L. (eds.).
The Geology of Continental Margins. New York, Springer-Verlag,
p. 921-931.
92
Douglass, R. C, 1967, "Permian Tethyan Fusulinids from California."
U. S. Geol. Survey Prof. Paper 59 3-A, 13 p.
Duffield, W. A., and Sharp, R. V., 1975, "Geology of the Sierra
Foothills Melange and Adjacent Areas, Amador County, California.'
U. S. Geol. Survey Prof. Paper 827, 30 p.
Durrell, C, 1959a, "Tertiary Stratigraphy of the Blairsden
Quadrangle, Plumas County, California." Univ. Calif. Pub.
Geol. Sci., V. 34, p. 161-192.
1959b, "The Love joy Formation of Northern California."
California Univ., Dept. Geol. Sci. Bull., v. 34, n. 4,
p. 193-220.
1966, "Tertiary and Quaternary Geology of the Northern Sierra
Nevada," _in Bailey, E. H. (ed.). Geology of Northern California.
Calif. Div. Mines and Geol. Bull. 190, p. 185-197.
Erwin, H. D., 1934, "Geology and Mineral Resources of Northeastern
Madera County, California." Calif. Jour. Mines and Geol.,
V. 30, p. 7-78.
Evernden, J. F., and Kistler, R. W. , 1970, "Chronology of Emplacement
of Mesozoic Batholithic Complexes in California and Western
Nevada." U. S. Geol. Survey Prof. Paper 62 3, 42 p.
Evernden, J. F., Savage, D. E., Curtis, G. H. , and James, G. T. ,
1964, "Potassium-argon Dates and the Cenozoic Mammalian
Chronology of North America." Amer. Jour. Sci., v. 262,
p. 145-198.
Ferguson, H. G., and Gannett, R. W. , 1932, "Gold Quartz Veins of
the Allegheny District, California," U. S. Geol. Survey Prof.
Paper 172, 13 p.
Fontaine, W. M. , 1900, "Notes on Mesozoic Plants from Oroville,
California," _in Ward, L. F. (ed.). Status of the Mesozoic
Floras of the United States. U. S. Geol. Survey Ann. Rept . ,
V. 20, p. 342-368.
Gabb, W. M. , 1869, "Cretaceous and Tertiary Fossils." Calif. Geol.
Survey, Paleontology of California, v. 2, 299 p.
Gansser, A., 1974, "The Qphiolite Melange, a World-v/ide Problem on
Tethyan Examples." Eclogae Geol. Helv. , v. 67/3, p. 479-507.
Gass, I, G. , and Smewing, J. D., 1973, "Intrusion, Extrusion and
Metamorphism at Constructive Margins: Evidence from the Troodos
Massif, Cyprus." Nature (London), v. 242, p. 26-29.
Gilluly, J., 1972, "Tectonics Involved in the Evolution of Mountain
Ranges," Jji Robertson, E. C. (ed.). Nature of the Solid Earth.
New York, McGraw-Hill, p. 406-439.
93
Compton, R. R., 1955, "Trondhjemite Batholith near Bidwell Bar,
California." Geol. Soc. America Bull., v. 66, p. 9-44.
Creely, R. S., 1955, "Geology of the Oroville Quadrangle." Ph.D.
thesis, Univ. of California, Berkeley, 269 p.
1965, "Geology of the Oroville Quadrangle, California." Calif.
Div. Mines and Geol., Bull. 184, 86 p.
Dalrymple, G. B., 1964, "Cenozoic Chronology of the Sierra Nevada,
California." Univ. Calif. Pubs. Geol. Sci., v. 47, p. 1-41.
Davis, G. A., 1969, "Tectonic Correlations, Klamath Mountains and
Western Sierra Nevada, California." Geol. Soc. America Bull.,
V. 80, n. 6, p. 1095-1108.
Day, D., 1977, "Petrology and Intrusive Complexities of Sheeted
Dikes in the Smartville Ophiolite, Northwestern Sierra
Foothills, California" (abs.): Geol. Soc. America Abstracts
With Programs, v. 9, n. 4, p. 410.
Dewey, J. F., and Bird, J. M. , 1970, "Mountain Belts and the New
Global Tectonics." Jour. Geophys. Research, v. 75, p. 2625-2647.
Dickerson, R. E., 1916, "Stratigraphy and Fauna of the Tejon Eocene
of California." Univ. Calif. Pub- Bull. Dept . Geol. Sci., v. 9,
p. 363-524.
Dickinson, W. R. , 1968, "Circum-Pacif ic Andesite Types." Jour.
Geophys. Research, v. 73, p. 2261-2269.
1969, "Evolution of Calc-alkaline Rocks in the Geosynclinal
System of California and Oregon." Oregon Dept. Geol. and Min.
Industries Bull. 65, p. 151-156.
1975, "Time-Transgressive Tectonic Contacts Bordering Subduction
Complexes" (abs.); Geol. Soc. America Abstracts with Programs,
V. 7, n. 7, p. 1052.
Dickinson, W. R., and Hatherton, T., 1967, "Andesitic Volcanism and
Seismicity around the Pacific." Science, v. 157, p. 801-803.
Diller, J. S., 1892, "Geology of the Taylorsville Region of
California." Geol. Soc. America Bull., v. 3, p. 369-394.
1895, "Lassen Peak Folio." U, S. Geol. Survey Atlas, n. 15.
1908, "Geology of the Taylorsville Region, California." U. S.
Geol. Survey Bull. 353, 128 p.
Diller, J. S., and Stanton, T. W. , 1894, "The Shasta-Chico Series."
Geol. Soc. America Bull., v. 5, p. 435-464.
94
Gromme, C. S., Merrill, R. T. , and Verhoogen, J., 1967,
"Paleomagnetism of Jurassic and Cretaceous Plutonic Rocks in
the Sierra Nevada, California, and its Significance for Polar
Wandering and Continental Drift." Jour. Geophys. Research,
V. 72, p. 5661-5684.
Gupta, H. K. , Rastogi, B. K., and Narain, H., 1973, "Earthquakes in
the Koyna Region and Common Features of the Reservoir-associated
Seismicity," j^Ackerman, W. C, White, G. F., and Worthington,
y E. B. (eds.). Man-made Lakes: Their Problems and Environmental
Effects : Amer . Geophys. Union, Geophy. Mono. 17, p. 455-46 7.
Hamilton, W. , 1969, "Mesozoic California and the Underflow of
Pacific Mantle." Geol. Soc. America Bull., v. 80, n. 12, p.
2409-2430.
Hamilton, W. , and Myers, W. B. , 1966, "Cenozoic Tectonics of the
Western United States." Rev. Geophysics, v. 4, p. 509-549.
Harland, W. B., Smith, A. C, and Wilcock, B. , eds., 1964, "The
Phanerozoic Time-scale - A symposium dedicated to Professor
Arthur Holmes." Geol. Soc. London Quart. Jour. Supp. , v. 1205,
458 p.
Hay, E. A., 1976, "Cenozoic Uplifting of the Sierra Nevada in
Isostatic Response to North American and Pacific Plate
Interactions." Geology , v. 4, n. 12, p. 763-766.
Hess, H. H., 1959, "Nature of the Great Oceanic Ridges." Internat.
Ocean. Cong. Preprints, Am. Assoc. Adv. Sci., p. 33-34.
1962, "History of Ocean Basins," iri Engel, A. E. J., James,
H. L., and Leonard, B. F. (eds.), Petrologic studies: a volume
to honor A. F. Buddinqton. Geol. Soc. America, p. 599-620.
Hietanen, A., 1951, "Metamorphic and Igneous Rocks of the Merrimac
Area, Plumas National Forest, California." Geol. Soc. America
Bull., V. 62, p. 565-608.
1973a, "Geology of the Pulga and Bucks Lake Quadrangles, Butte
and Plumas Counties, California." U. S. Geol. Survey Prof.
Paper 731, 66 p.
1973b, "Origin of Andesitic and Granitic Magmas in the Northern
Sierra Nevada, California." Geol. Soc. America Bull., v. 84,
p. 2111-2118.
1976, "Metamorphism and Plutonism around the Middle and South
Forks, Feather River, California." U. S. Geol. Survey Prof.
Paper 920, 3o p.
1977, Paleozoic-Mesozoic Boundary in the Berry Creek Quadrangle,
Northwestern Sierra Nevada, California." U. S. Geol. Survey
Prof. Paper 1027, 22 p.
95
Hudson, F. S., 1951, "Mount Lincoln-Castle Peak Area, Sierra Nevada,
California." Geol . Soc . America Bull., v. 62, p. 931-952.
1955, "Measurement of the Deformation of the Sierra Nevada,
California, since Middle Eocene." Geol. Soc. America Bull.,
V. 66, p. 835-870.
Hsu, K. J., 1966, "Melange Concept and its Application to an Inter-
pretation of the California Coast Range Geology." ( abs . ) Geol.
Soc. America Abstracts for 1966, n. 101, p. 99-100.
1968, "Principles of Melanges and Their Bearing on the
Franciscan-Knoxville Paradox." Geol. Soc. America Bull., v. 79,
p. 1063-1074.
1971, "Franciscan Melanges as a Model for Eugeosynclinal
Sedimentation and Underthrusting Tectonics." Jour. Geophys .
Research, v. 76, p. 1162-1170.
Imlay, R. W, , 1961, "Late Jurassic Ammonites from the Western Sierra
Nevada, California." U. S. Geol. Survey Prof. Paper 374-D,
30 p.
Irwin, W. P., 1972, "Terranes of the Western Paleozoic and Triassic
Belt in the Southern Klamath Mountains, California." U. S.
Geol. Survey Prof. Paper 800-C, p. C103-C111.
Irwin, W. P., and Galanis, S. P., 1976, Map showing limestone and
selected fossil localities in the Klamath Mountains, California
and Oregon. U. S. Geol. Survey Misc. Field Studies Map MF-749,
scale 1:500,000.
Irwin, W. P., Jones, D. L., and Pessagno, E. A., Jr., 1977,
"Significance of Mesozoic Radiolarians from the Pre-Nevadan
Rocks of the Southern Klamath Mountains, California." Geology,
V. 5, p. 557-562.
Jackson, E, D., Green, H. W. , II, and Moores, E. M. , 1975, "The
Vourinos Ophiolite, Greece: Cyclic Units of Lineated Cumulates
Overlying Harzburgite Tectonite." Geol. Soc. America Bull.,
V. 86, p. 390-398.
Jennings, C. W. , 1975, Fault map of California: Calif. Div. Mines and
Geol., scale 1:750,000.
1977, Geologic map of California: Calif. Div. Mines and Geol.,
scale 1:750,000.
Karig, D. E., 1970, "Ridges and Basins of the Tonga-Kermadec Island
Arc System." Jour. Geophys. Research, v. 75, p. 239-255.
1971a, "Structural History of the Mariana Island Arc System."
Geol. Soc. America Bull., v. 82, p. 323-344.
96
1971b, "Origin and Development of Marginal Basins in the
Western Pacific." Jour. Geophys. Research, v. 76, p. 2542-2561.
1972, "Remnant Arcs." Geol. Soc. America Bull., v. 83,
p. 1057-1068.
1974, "Evolution of Arc Systems in the Western Pacific." Ann.
Rev. Earth and Planetary Sci., v. 2, p. 51-76.
Karig, D. E., and Sharman, G. F., Ill, 1975, "Subduction and
Accretion in Trenches." Geol. Soc. America Bull., v. 86,
p. 377-389.
Knopf, A., 1918, "Geology and Ore Deposits of the Yerrington District
Nevada." U. S. Geol. Survey Prof. Paper 114, 68 p.
1929, "Mother Lode System of California." U. S. Geol. Survey
Prof. Paper 157, 88 p.
Knowlton, F. H. , 1910, "The Jurassic Age of the "Jurassic Flora of
Oregon'." Am. Jour. Sci., v. 30, p. 33-64.
Lahr, K. M. , Lahr , J. C., Lindh, A. G. , Bufe, C. G. , and Lester,
F. W., 1976, "The August 1975 Oroville Earthquakes." Seis.
Soc. America Bull., v. 66, n. 4, p. 1085-1099.
Langstrom, C. A., and Bulter, R., 1976, "Focal Mechanism of the
August 1, 1975, Oroville Earthquake." Seis. Soc. America
Bull., V. 66, n. 4, p. 1111-1120.
Lapham, D. M. , and McKague , H. W. , 1964, "Structural Patterns
Associated with the Serpentinites of Southeastern Pennsylvania."
Geol. Soc. America Bull., v. 75, p. 639-660.
Lester, F. W. , Bufe, C. G. , Lahr, K. M. , and Stewart, S. W. , 1975,
"Aftershocks of the Oroville Earthquake of August 1, 1975,"
in Sherburne, R. W. , and Hauge, C. J. ( eds . ) , Oroville ,
California Earthquake 1 August 1975. Calif. Div. Mines and
Geol. Spec. Rept . 124, p. 131-138.
Lindgren, W. , 1894, "Sacramento, Calif ornia" : U. S. Geol. Survey
Geol. Atlas, Folio 5, 3 p., scale 1:125,000.
1900, "Description of the Colfax Quadrangle (California)."
U. S. Geol. Survey Geol. Atlas, Folio 66, 10 p., scale
1:125,000.
1911, "The Tertiary Gravels of the Sierra Nevada of California."
U. S. Geol. Survey Prof. Paper 73, 226 p.
Lindgren, W. , and Turner, H. W. , 1895 "Smartsville" :U. S. Geol.
Survey Geol. Atlas, Folio 18, 6 p., scale 1:125,000.
97
Lockwood, J. P., 1971, "Sedimentary and Gravity-Slide Emplacement
of Serpentinite. " Geol . Soc. America Bull., v. 82, p. 919-936.
1972, "Possible Mechanisms for the Emplacement of Alpine-type
Serpentinite." Geol. Soc. America Mem. 132, p. 273-287.
Lomnitz, C., and Bolt, B. A., 1967, "Evidence on Crustal Structure in
California from the Chase V Explosion and the Chico Earthquake
of May 24, 1966." Seis. Soc. America, v. 57, n. 5, p. 1093-1114
Lydon, P. A., 1968, "Geology and Lahars of the Tuscan Formation,
Northern California." Geol. Soc. America Mem. 116, p. 441-475.
Lydon, P. A., Gay, T. E., Jr., and Jennings, C. W. (compilers), 1960,
Geologic map of California, Westwood sheet: Calif. Div. Mines
and Geol., scale 1:250,000.
Mayo, E., 1934, "Geology and Mineral Resources of Laurel and Convict
Basins, Southwestern Mono County, California." Calif. Jour.
Mines and Geol., v. 30, p. 79-87.
1935, "Some Intrusions and Their Wall Rocks in the Sierra
Nevada." Jour. Geol., v. 43, p. 673-689.
Moberly, R. , 1972, "Origin of Lithosphere Behind Island Arcs, with
References to the Western Pacific." Geol. Soc. America Mem.
132, p. 35-55.
Mogi, K,, 1963, "Some Discussions on Aftershocks, Foreshocks and
Earthquake Swarms - the Fracture of a Semi-infinite Body ^^
caused by an Inner Stress Origin and its Relation to the
Earthquake Phenomena." Earthquake Res. Inst. Bull., v. 41,
p. 615-658. /
Moore, J. G., 1959, "The Quartz Diorite Boundary Line in the Western
United States." Jour. Geol., v. 67, p. 198-210.
1973, "Complex Deformation of Cretaceous Trench Deposits, South-
western Alaska." Geol. Soc. America Bull., v. 84, p. 2005-2020.
Moores, E. M. , 1972, "Model for Jurassic Island Arc-Continental
Margin Collision in California" (abs.). Geol. Soc. America
Abstracts with Programs, v. 4, n. 3, p. 202.
1975, "The Smartville Terrane, Northwestern Sierra Nevada, a
Major Pre-Late Jurassic Ophiolite Complex" (abs.). Geol. Soc.
America Abstracts with Programs, v. 7, n. 3, p. 352.
Moores, E. M. , and Jackson, E. D., 1974, "A Comparison of Selected
Ophiolites and Oceanic Crust." Nature, v. 250, p. 136-139.
Moores, E. M., and Vine, F., 1971, "The Troodos Massif, Cyprus and
Other Ophiolites as Oceanic Crust: Evaluation and Complications
Royal Soc. London Trans., Se. A. v. 268, p. 443-466.
98
Morrison, P. W. , Jr., 1974, "Report of Seismic Activity Near Lake
Oroville January 1969 - December 1972." Calif. Dept. Water
Res., Earthquake Engr . Memorandum n. 61, 60 p.
Morrison, P. W. , Jr., Stump, B. W., and Uhrhammer, R. , 1976, "The
Oroville Earthquake Sequence of August 1975." Seis. Soc.
America Bull., v. 66, n. 4, p. 1065-1084.
Popenoe, W. P., 1943, "Cretaceous, East Side Sacramento Valley,
Shasta and Butte Counties, California." Am. Assoc. Pet. Geol
Bull., v. 27, p. 306-312.
Radbruch-Hall, D. H,, Colton, R. B., Davies, W. E., Skipp, B. A.,
Luchitta, I., and Varnes, D. J., 1976, Preliminary Landslide
Overview Map of the Conterminous United States: U. S. Geol.
Survey Misc. Field Studies MF-771, scale 1:7,500,000.
Raymond, L. A., 1977, "Emplacement of Exotic Tectonic Blocks in
the Franciscan Complex, Northern Diablo Range, California"
(abs.). Geol. Soc. America Abstracts with Programs, v. 9,
n. 4, p. 486.
Rothe, J. P., 1969, "Earthquakes and Reservoir Loading."
A- Proceedings , Fourth World Conference on Earthquake Engineering
\ Chile, V. 1, p. A28-A38C.
1973, "Summary: Geophysics Report," in Ackerman , W. C, White,
G. T., and Worthington, E. B. ( eds . ) , Man-Made Lakes: Their
Problems and Environmental Effects. Am. Geophys . Union,
Geophysical Monograph 17, p. 441-454.
Russel, L. R., 1978, "The Melones Fault Zone and the Tectonic
Framework of the Western Sierra Nevada Between the Middle and
South Forks of the American River, California" (abs.). Geol
Soc. America Abstracts with Programs, v. 10, n. 3, p. 145.
Scholl, D, W. , and Marlow, M. S., 1974, "Deposits in Magmatic Arc
and Trench Systems: Sedimentary Sequence in Modern Pacific
Trenches and the Deformed Circum-Pacif ic Eugeosyncline , " jji
Dott, R. H., Jr., and Shaver, R. H. (eds.). Modern and Ancient
Geosynclinal Sedimentation: Soc. Econ . Paleon. Mineral. Spec.
Pub. 19, p. 193-211.
Schweickert, R. A., 1976, "Early Mesozoic Rifting and Fragmentation
of the Cordilleran Orogen in the Western USA." Nature, v. 260,
p. 586-591.
Schweickert, R. A., and Cowan, D. S., 1975, "Early Mesozoic Tectonic
Evolution of the Western Sierra Nevada, California." Geol.
Soc- America Bull., v. 86, p. 1329-1336.
99
Schweickert, R. A., and Wright, W. H. , 1975, "Preliminary Evidence
of the Tectonic History of the Calaveras Formation of the
Western Sierra Nevada, California" (abs,). Geol. Soc. America
Abstracts with Programs, v. 7, n. 3, p. 371-372.
Standlee, L. A., 1978, "Middle Paleozoic Ophiolite in the Melones
Fault Zone, Northern Sierra Nevada, California" (abs.). Geol.
Soc. America Abstracts with Programs, v. 10, n. 3, p. 148.
Stanton, T. W. , 1896, "The Faunal Relations of the Eocene and Upper
Cretaceous on the Pacific Coast." U. S. Geol. Survey
Seventeenth Ann. Rept . , p. 1005-1060.
Strand, R. G., and Koenig, J. B., 1965, Geologic Map of California,
Olaf P. Jenkins Edition, Sacramento Sheet: Calif. Div. Mines
and Geol., scale 1:250,000.
Swan, F. H., Ill, and Hanson, K. L., 1977, "Quaternary Geology
and Age Dating," jji Woodward-Clyde Consultants, Earthquake
Evaluation Studies of the Auburn Dam Area: Woodward-Clyde
Consultants, unpublished, v. 4, 83 p.
Swan, F. H., Ill, and Hanson, K. L. , 1978, "Origin and Ages of Late
Quaternary Deposits and Buried Paleosols in the Western Sierra
Nevada Foothills, California" (abs.). Geol. Soc. America
Abstracts with Programs, v. 10, n. 3, p. 149.
Taff, J. A., Hanna, G. D., and Cross, C. M. , 1940, "Type Locality
of the Cretaceous Chico Formation." Geol. Soc. America Bull.,
V. 51, p. 1311-1328.
Taliaferro, N. L., 1942, "Geologic History and Correlation of the
Jurassic of Southwestern Oregon and California." Geol. Soc.
America Bull., v. 53, p. 71-112.
1943, "Manganese Deposits of the Sierra Nevada, Their Genesis
and Metamorphism, " iri Jenkins, O. P. (ed.). Manganese in
California. Dept . Nat. Res., Div. Mines Bull. 125, p. 277-332.
1951, "Geology of the San Francisco Bay Counties." Calif. Dept,
Nat. Res,, Div. Mines Bull. 154, p. 117-150.
Townley, S. D,, and Allen, M. W., 1939, "Descriptive Catalog of
Earthquakes of the Pacific Coast of the United States 1769-1928,
Seis. Soc. America Bull., v. 29, n. 1, 297 p.
Turner, H. W. , 1893, "Some Recent Contributions to the Geology of
California." Am. Geologist, v. 11, p. 307-495.
1894, "The Rocks of the Sierra Nevada." U. S. Geol. Survey
Fourteenth Ann. Rept., p. 435-495.
1896, "Further Contributions to the Geology of the Sierra
Nevada." U. S. Geol. Survey Seventeenth Ann. Rept., p. 521-762.
100
Tysdal, R. G. , Case, J. E., Wrinkler, G. R., and Clark, S. H. B. ,
1911 , "Sheeted Dikes, Gabbro and Pillow Basalt in Flysch of
Coastal Southern Alaska." Geology, v. 6, n. 3, p. 377-383.
U. S. Army Corps of Engineers, 1977, "Fault Evaluation Study,
Marysville Lake Project, Parks Bar Alternate, Yuba River,
California." U. S. A. C. of Eng . , Sacto. Dist., 25 p.
U. S, Geological Survey Staff, 1978, "Technical Review of Earthquake
Evaluation Studies of the Auburn Dam Area (Woodward-Clyde
Consultants, 1977) — a report to the U. S. Bureau of Reclamation,
U. S. Geol. Survey, 143 p.
von Huene , R., 1972, "Structure of the Continental Margin and
Tectonism at the Eastern Aleutian Trench." Geol. Soc . America
Bull., V. 83, p. 3613-3626.
Whitney, J. D., 1865, "Report of the Progress and Synopsis of the
Field Work from 1860-1864." Geol. Survey of Calif., Geology,
V. 1, 498 p.
Williams, H. , and Stevens, R. K., 1974, "The Ancient Continental
Margin of Eastern North America," _in Burk, C. A., and Drake,
C. L. ( eds . ) The Geology of the Continental Margins: New York,
Springer-Verlag, p. 781-796.
Wolfe, J. E., 1967, "Earthquake Hazard Report (n. 28) for the State
Water Project - Oroville Dam Site." California Dept . Water
Res. , 9 p.
Wood, H. O., and Heck, N. H., 1951, "Earthquake History of the
United States, 1769-1950, Part II, Stronger Earthquakes of
California and Western Nevada." U. S. Dept. of Commerce,
Coast and Geodetic Sur., n. 609.
Woodward-Clyde Consultants, 19 77, "Earthquake Evaluation Studies
of the Auburn Dam Area," report prepared for the U. S. Bureau
of Reclamation, 8 volumes.
Wright, L., 1976, "Late Cenozoic Fault Patterns and Stress Fields
in the Great Basin and Westward Displacement of the Sierra
Nevada Block." Geology, v. 4, n. 8, p. 489-494.
Xenophontos, C, and Bond, G. C, 1978, "Petrology, Sedimentation
and Paleogeography of the Smartville Terrane (Jurrasic) -
bearing on the Genesis of the Smartville Ophiolite," _in Howell,
D. G., and McDougall, K. A. (eds.), Mesozoic Peleogeography
of the Western United States: Soc. Econ . Paleon. Mineral.,
Pac. Sect., p. 291-302.
101
ADDENDA TO CHAPTER II
Department of Water Resources
Exploration Trench Logs
9—78786 103
MODERATELY
FRACTURED ROCK
STRONGLY
FRACTURED ROCK
STIFF RED CLAY
STRONGLY FOLIATED ROCK
TRENCH A
BRECCIA
TRENCH B
SOFT BROWN CLAY
FRACTURED ROCK
Rock: Metovolcontc, dork groy to greenish-groy, massive to strongly foliated, moderately to strongly fractured, frocture surfaces
commonly limonite stoined, grades from strongly weathered near soil contoct to moderately weatfiered ot deptfi.
Breccio: Crushed frogments of metovolcanic rock, generally with some cloy matrix.
Gouge: Plastic cloy, grades from reddish-brown near soil contact to greentsh-groy ot depth.
Soil: Silty, reddish-brown, friobie, residual soil.
Logs of Exploration Trenches Along Cleveland Hill Crack Zone
104
r^ _
I- 5 to
® © © ® ©
© © ©
© © ©
i33J
105
i33d
~,S3Ul2n
0/
^
5l
0
ii isj ^-i i§ :-i e -j
p IP II II is ^ |i
i| ip ii ii ^B I I?
iss ios if is' II I is"
© © © © © 0©
-^ t-
o: O o
© ©
S3MJ.3WO
X33JO
uJS3Mi3W
1333*'
106
S3Mi3W
i33i_
:iS3ai3w
to '" I
o >
llJ < ^
< uj 5
(r -J *
-J > ? !;
Q- 2 ^ o
liJ -. F. u-
-S
°s I i
5." g g
© (D ©
S3Hi3W
i333if
<l> IE ujS3bl3n
107
108
133JO
S3Mi3>MO
1333
:;s3ai3w
t-
<
o
_i
Q.
X
UJ
® © ©
■ ! 11®
© © ®
109
i33JO
o
ICw 1333
m
2
S3di3no
-
CVJ
m
■^ 1- !i;s3yi3w
^
u O
5 If
^ ^ t; <o
\
Pj_S < UJ N.
-'
O „ 1
1
(•(jj
OG
VESTI
N 80'
5-24
1
1
§^1^
■s
1
-
- --^ss
-
-
o_
100
RENCH
EAMENT
OF TREN
ATE LOGG
:. COLE
1
A
•
-
95
ON Tl
REA LIN
BEARING
D
AND K
1
/ »0
- i= < li 2
1
b,\
"*»
m
on -i * <
0,° 0
-'
.
rj-
'
• O d X ^
.o _| > 1- Q:
/o 0 °
1
W»
"
Q- ° <^ § >
■ i*< o - ^ "
D 0 D
UJ X i.^ o
1
(D 1
(D
0 ''.o'
o.
= h
s-
85
ROJECT:
TRENC
LOG 01
LOGGE
1
o° 0
Q.
1
O'Oo
b *^<
.o
1
» 0 »°
1
) 0°
\
I
'°o°°
\
0
\
o
(
/ oo "^^
\
"m
0 0 <
m-
\
«.
-
/
PK
\
%^^^
CM
.
" w
1 ^
1
1 V
-
L PS "oi?
1 \^
.
1
U^of
■
I \
in
1
1 >
,
'p^
1
\^k
\
•
0°^.
.o
\
"
I
o?o"
u,-
\
N"
•
1
)C?" ?fl
\
.
^O'Q
i\
».»0° "
.o
1
-
\
f^
1
F
-«
1
E
I
/
^-
(D 1
(D
^0 M
o.
-s j [ jj
/
-
-O
1
Icl
-
- ^J I ll
J
'>/!
,'»!»
-O gjo °t I
J
-,n
m
P l_i S; i
1
-
j®
-
-s 1 !? H !
"
/
f;
; © ® © ©
%ly
1
iO
l/> H
S !l
S3ai3WO
7
7
?
f ^ a uJS3al3Hp -
■NJ
,<, <r
H t;^
i33Jo
"
2
■n^ 133JO ' ' ' ' J>
2
— 1 UJ
no
i33dO
S3MJ.3WO
S3ai3WO
I—
i33dO
-■- Z kJ
UJ < ^
•^ li ?
a:
0(1:01
I- <
O =!
_l >
Q_ O O
X Q ..
UJ ^
•- ^
o S
0=0 0
® ©0
© © ©
ni
i33dtp , ^ ^ , '^ , , , , ° , , , , '^^, 1333
s ^
S3ai3WO - ~ -^ -i ' ^ t;s3ai3w
^ \L O S ~
UI uj — 1 U.
s ir
< ;s °
///
»■
-.
H LOG
IT INVESTIG
;NCH: N 82 E
GGED: 5-25a;
SHEET 2
4 vV;\
■"
' © \
"
. o m ^ 3 ^ :
^ 2 Ui O ,
°l / z'
-S
UJ < fe K <-> '
Q' ^ ° < .:
* .
■?
ORATION Tl
ILLE AREA LIN
BEARING
H WALL D
I AKERS AND K
1 /
"
_l > 1- "-
1/
o
EXP
: ORO
:h: 10
F NOR
D BY:
[ ©
-<3-
JECT
TRENC
LOG 0
LOGGE
1 /
v"
-
PRO
yAi!
-
■
\) 1 /'
■§
11
"
i'
1 1
N
'^
oi
I
s-
.,
■ lis
\ (D
;
- <Jl
\
.
>
•
©
/
o
/
-OJ
.
/
<0.
K
tM
< £ > o
®) 'X\
;
\
-" ll III ^
/ \
1 )
\
-5
\\
- 11 sp ^
1 ^-~/
■
0 lA
~< i o ^ ^
' fio)
ly. \
^ I o 1- u. 5
/ ^^
/
1
I
\
\
*.
;?
'\/\
o.
.
/ \
-^ Hi HJ° S
/
1 r~\ 1
-
' ®\
i
(eW
m
', /\
: © © ®
^
in 1-
UJ IZ
S3Mi3WO - « 1^ ? , 2 iuS3ai3Wp y w
? ? ,^ li*
13330 ' ' ' ' J, ' ' ' ' g ' ' ' ' lOs 13330 ' ' ' ' j, ' ' ' '
O ^£12
112
i33J
"S3ai3H
I- <
<t LlI
O =!
-I > -.^
Q. ° - '^
^ = o
UJ .. I u.
H ^ O
LiJ q: o
-> I-
O
(r
CL
0,
. 0® ©
S3ai3HO
13330
IE 11JS3813WO
lU
Si -rO
iili Ul ^\
5 I W g ; "
« ^ ° S " i
» » t-
:5s I j-sglij
y§*a uiSs ^sa ^6 ^i il ^ i
?32^ isss eS3 si fe^ d| I a
g;;;-ii iiss ^|£ ^g =< ;;5 3 5
Iili iisi ill if ii ig 3 d
© © ® ® © © 0©
, ®
3i
3d
is
I- S 5!
o >
llJ <
a: ^
<
LlJ
<
Ul
rr
_l
<
o
I
(£
1
>
H
Q.
O
o
CM
V
X
Z
01
111
I
o
1-
o
Z
UJ
O
o
UJ
o
It
o
o
® ill
o Si y ,i ii: o
© ©
"" si £§ *!'
III i£| is
© « H © © ©
n't
o
111
?•
O
o
>
_l
z
Q
< )
liJ
X
o
z
liJ
tr.
1-
1-
z
LlI
<
Ul
z
cc
1-
u.
o
o
O
O
-1
UJ
1-
<
-I
o
o
o
<
LlI
<
llJ
OD
z
<
1-
<
-J
-1
q:
<
LlI
<
rr
_l
<
o
X
1
>
Q.
X
O
tr
o
12
o
z
>-
to
III
X
o
H
?■
o
LlJ
iLl
<■)
IT
o
O
O
©
■lie
K © ®
115
J!/4
©1 ®
I ^i
\ @
o,®
8--
O >
UJ <
a: ^
^ K _l _l
XX6
S3tll3W <
3?
t- o 1-
o >
z —
5 V "
t X S
KS
i s " g
i S 6 S
© ©
o =)
_l >
Q- O
i^f!i
i g s K ;. g
\-0 gg-R"^
©
> i o S S = "
f 4 z 3 3 o <
j o ^ vj B a I
I' I i o Fi I
-s IllPg^
^25 S - d *
H "« E V h S ;
©
ki -/
.•<5
@
f<r?
^ r-^
/V •''
U S
■Y
' .^
a. uiS3U13n
■>'ii i33d^
O >
_l z
ai <
<
UJ
<
UJ
nr
_i
o
o
_i
I
^
1
>
l-
Q.
X
o
tr
o
lO
o
z
>■
CD
liJ
X
a
(-
o
UJ
o
UJ
LlI
IT
o
1-
-1
-I
118
i33JO
saaiano
-8
©0
a 2»> £ :
idiii gE
<
^- L
to trt 5
*-* IJJ z
O >
-> ? i
o
-*- ^ iij
2 5'-
UJ < fe
tr ^
r- z 13
•- =i ?
a:
^ UJ UJ
O a: "0
H <
<t LlI
O d
_l >
Q. O !£>
O uj
o
>-
it)
o
n
w
to
(.9
o
O
I! ®
il^ ill il!lli| I I iM III
---z 91^^ "^R-. Jiui^t^ *, « y 5* o pSffi
®
iN;
® ® © © ©© ©0 ®®
119
i33dO
^
1 9
-12
^
H tD 0
S3Mi3WO
-1.
N Ki ■i
H
5 if
S "- 1- CO
.0
105
OG
VESTIGA
EAST - WE
6-17-77
IN
■
100
CH L
ENT IN
•rench:
logged:
McJUNKI
T-
0.
Z 5 •- E
.0
■
95
ATION TRE
E AREA LINEA
BEARING OF
^all date
le, m. hausladen,
-"
.
<M-
tt: -1 * 8
-
■ 0 - ^ ^
.0 _| > K ^
\
■S
-
5 9
EXP
OJECT: ORO
trench: 16
LOG OF NOR
logged by.-
v\
■
CD q;
Q.
• *°^
£
.0
5
g
*
■
-
(Dl^l-^
3
o
■
d
\^
1
.0
£
i
dki®
1
ii
■s
*.
-
y
S I
g
'*A
1
s
''M
58
.
-
V
1
01
i ®
Si
ii
.0
■ N
1 S
' ^*^*~^
1 °
1 t
\ *'^''V^
. ^
•
;„ ;. 2
/ ©
>
■
.0
N
^ s Z
= 5 "
A-. is
"
.
^ i i
( ^^/^
-
" " s
A®
■-
,s
•
'\/
-
■
"iii^s \
0.
■s
1
■°/
i|iss? 1
5
/
f
.0
t ?? J g g* °
yfiii i
\
•
/
.-
■
1 J ^ 1 i s 1
i
5-
•"
/
■■"
5|ss|f 8^
1
.
/
tt^N^Iui i
S
/
-
"Si^ga If
3
5
"
-s
K
/
0 ©
© ©
(D
S \f
0-
-0
^-
ssaiswo -;■
" ? T
^^ ^
K \L
i33JO u
"i Q
-2
s
120
0>
£^©
iSK
-! is §!§
^ i
as;
I- O) ^ O
< ^ f:
LlI
o >
w t;;
— <j UJ
-r h- z "> S
X ^ S o i:
r: z o Q ^
I- <
^ Ll)
O d
_l >
Q.
X
O 1^ oc
q; - O
is" IS °°= °i3 ^.s^tSS ^ =^ ¥ -
0 ® ® © © ©©0©
S3«i3WO
I—
i33JO
121
CHAPTER III
SEISMOLOGY
Introduction
Bulletin 203, April 1977, reported
earthquakes , Richter magnitude 2 . 5 and
greater, of the Oroville sequence through
March 1976. This report will present
the data recorded from June 1, 1975,
through May 31, 1978, Richter magnitude
1.0 and greater.
Figure 58 shows the combined DWR-USGS
telemetered seimographic network as it
was variously composed throughout the
sequence. Since about August 1976, when
the USGS network was considerably
reduced, the network has remained essen-
tially unchanged. The table in Figure 58
shows the DWR network as it was variously
composed from June 1, 1975 to May 31,
1978.
Data
Epicenters of earthquakes of magnitude
1.0 and greater for 1975 and 1976-78
are plotted in Figures 59 and 63, respec-
tively. The hypocenters are listed on
Tables 3 and 4 . The aftershock zone , as
shown in Figures 59 and 63, is parti-
tioned into north, middle, and south
sections . The hypocenters from each
section are projected onto a vertical
east-west striking plane, shown in
Figures 60 through 62 and 64 through 66.
Figure 67 is a vertical cross-section of
the middle section for events recorded
between August 2 at 1400 GMT and
December 31, 1975.
Surface cracking was observed on Cleve-
land Hill to the east of the aftershock
zone soon after the mainshock. The ver-
tical cross-sections show that the fault
plane surfaces near the cracks. The
fault was sxibsequently named the Cleve-
land Hill Fault. The Department recorded
network as recounted in the table on
Figure 58, was composed of MGL, ORV, KPK,
DOG, BUT and SUT, from July 1975 into
January 1976. Note that OSTI and OHON
were added in November 1975. From
January 1976 onward, the network
included additional stations PAM, and
OCAM.
Consequently, to make the Department
network of August through December 1975
more nearly equivalent to the network
of 1976 onward, the U. S. Geological
Survey in Menlo Park supplied the P-times
for aftershocks from Woodward- Clyde
portable stations WCl, WC2, WC3, and
WC4 and USGS Stations OCAM, OHON, OSTI,
OWYN and ORAT. Times from Woodward-
Clyde stations were available for events
recorded on August 2 at 1454 GMT through
August 12 at 1945 GMT. Times were avail-
able for the event recorded August 5 at
0228 GMT through December 1975.
Installation of the USGS network stations
began soon after the August 1 mainshock,
and recording was initially accomplished
on magnetic tape beginning August 5, 1975.
By August 16, 1975, a telemetry link to
Menlo Park was established so that their
stations were thereafter recorded on 16
mm. film. Woodward -Clyde installed
four portable stations in the aftershock
area beginning August 2, 1975.
Hypocenters were determined by the USGS
Hypo 71 hypocenter program (1) * and
the Byerly Crustal model. Station correc-
tions were determined by averaging the
hypocenter residuals of a number of
well recorded events.
Magnitudes were determined by two methods:
1 . The duration method : Magnitude-
duration curves were plotted for
the Oroville and Jamestown (not
shown in Figure 58) short-period
vertical seismometers. The elapsed
time from the initial seismic P-wave
(1) Number refers to reference listed at the end of the Chapter.
123
onset to the time the maximum seismic
trace amplitude falls consistently
below an arbitrary level is plotted
against "known" earthquake magnitudes.
This provides a plot whereby the
magnitudes of subsequent events are
estimated (2) .
2. The equivalent Wood-Anderson seis-
mograph magnitude estimate is cal-
culated from the Oroville east-west
short-period seismometer response
(3).
Figure 68 is a time-plot of the Oroville
water surface elevation and the number of
aftershocks by month.
Results
Inspection of the epicentral plots
Figures 59 and 63 indicates a north-south
alignment of aftershocks confined within
a rectangle about 15 kilometres north-
south and 8 kilometres east-west. Inspec-
tion of Table 3 shows that on August 2
the main aftershock activity began to
shift to the north and south sections of
the apparent fault rupture. After
December 31, 1975, about 52 percent of
the aftershocks listed in Table 4 occur
in the south section (Figure 63) and
about 70 percent east of the 121.5 meri-
dian.
A 6CP angle to the west has been drawn
through the vertical cross sectional plots
in Figures 60, 61, 64, and 65 to indicate
the approximate dip of the fault break in
the north and middle portions of the rup-
ture zone. In Figure 61 at least two
alignments seem evident, one near 60° and
another about 35°. Most of the hypo-
centers in Figures 60 through 62 were
determined before good depth control was
available. Therefore, Figure 67 was
plotted beginning with events on August 2
when the first Woodward-Clyde station was
available. A near 60° alignment is evi-
dent in that figure. In Figure 62 no
clear alignment is evident.
Figure 66, as in Figure 62, shows no
clear alignment of hypocenters and prob-
ably indicates more than one rupture
plane .
Discussion
As in the seven years before the August 1,
1975, Oroville earthquake, subsequent
Lake Oroville water surface fluctuations
do not appear to affect nearby seismic
activity. The rapid filling of the res-
ervoir this past winter and spring (1977-
1978) does not, at this time, appear to
have influenced the slow decline of the
seismicity rate in the aftershock zone.
The near 60° dip of the Cleveland Hill
fault plane evident in the north and
middle cross-sectional plots is in agree-
ment with that reported by others (Lahr,
et al) (4) . Savage, et al (5) report
that the results of the repeat level
survey profiles across the aftershock
zone before and after August 1 are con-
sistent with about 0.36 m of normal slip
on the fault plane delineated by the
aftershock sequence .
Conclusions
Since August 1, 1975, a correlation is
not indicated between the Lake Oroville
water surface variations and the rate of
occurrence of Oroville aftershocks.
Within the boundary of the aftershock
zone north of 39°26'N latitude, vertical
cross-sectional plots indicate that the
Cleveland Hill Fault is a single, well
defined break, dipping to the west at
about 60° and with a near north-south
strike. Vertical cross sectional plots
south of 39°26'N indicate that the fault
breaks along more than one plane.
Figures 64 and 65 show single alignments
near 60 in the north and middle sections .
124
40 «
STATIONS RECORDED BY DWR
DURING THE OROVILLE SEQUENCE
STATION
DATE ON
DATE OFF
DRV
1963
PRESENT
KPK
1969
PRESENT
MGL
1966
PRESENT
PAM
76/1/20
PRESENT
BUT
75/7/1
PRESENT
SUT
75/7/1
76/12/12
DOG
75/8/2
76/8/6
OGAM
76/1/16
76/9/1
OHON
75/11/5
PRESENT
OSUT
76/9/1
PRESENT
OSTI
75/11/5
PRESENT
n MGL
D TELEMETERED STATION
A PORTABLE STATION
OSLO "O" PREFIX DESIGNATES USGS STATION
THE USGS STATIONS WERE ESTABLISHED
ON AUG. 6, 1975 OR SHORTLY THEREAFTER.
UNDERLINE DESIGNATES STATIONS CON-
TINUING IN OPERATION AFTER AUG. 1,1976
QOSHP
ABUT
Thermolito
After boy
□ OSUT
ASUT
39'
Figure 58. DWR-USGS Oroville Sensitive Sei sinograph i c Network
125
/ \r..w
^j^
• K • • •
^
~-o
,..
1
m;
- 39030
NORTH
-,(^
~n
^ ^
'ffyV^iJj-
X +
MIDDLE
I "tlh^'
"■^^
^^
m
-m
OWR TELEMETERED SEISMIC STATIONS
LEGEND
X
1 i
•^ <
2
+
2 <
M <
3/
CD
3 <
M <
4
A
4 <
M <
5
□
5 i
N <
6
IQ
SCBLE 1 : 192000
M* 1.0
Figure 59- Oroville Foreshocks, Mainshock, and Aftershocks; June 1, 1975"
December 31 , 1975
126
NORTH VERTICAL X-SECTION
EVENTS NORTH OF AND INCLUDING 39* 29.5' N
lU
CO
DISTfiNCElKM)
10 15
u: "
(E <
t 10
MS 1.0
Figure 60. 1975 Oroville Earthquake Hypocenters (North Vertical Cross Section)
MIDDLE VERTICAL X-SECTION
EVENTS BETWEEN 39" 29.5' N AND INCLUDING 39" 26.0' N
D[STfiNCE(KM)
10 15
< ^
(C <
1 I
Mil.O
Figure 61. 1975 Oroville Earthquake Hypocenters (Middle Vertical Cross Section)
127
SOUTH VERTICAL X-SECTION
EVENTS SOUTH OF 39" 26.0' N
DrSTfiNCEtKM)
ID 15
2Q
</>o
I I
25
-I 1 1 1 1 1 1 1 1 1 1 1 I H-f- 1^. IW — I 1 n 1 1 1 1 1 1 1 1 1
+ + + + ++1^*!% +
1 ID
+ ^
w^
+
+
X
M2:|.0
Figure 62. 1975 Oroville Earthquake Hypocenters (South Vertical Cross Section)
128
_EGEND
X
1
i
M
<
Z
+
z
i
-
<
3
o
3
^
M
<
4-
A
H
^
M
<
5
□
S
^
H
<
g
SCRLE 1 ••1920D0
Figure 63. Oroville Earthquake Epicenters (January I, 1 976-May ^1, 1978)
129
NORTH VERTICAL X-SECTION
EVENTS NORTH OF AND INCLUDING 39* 29.5' N
-I 1 1 r-
DLSTfiNCElKM)
.0 15
T 1 1 1 1 1 r
LlI
o ^
< ^
u. o
q: <
=3 a:
en o
I I
S5
-T 1 1 1 1 r
i 10
Q_
UJ
O
'» -I-
+ J- +
%
60
+ X
M^l.O
Figure 6A. Oroville Earthquake Hypocenters, 1976-May 31, 1978
(North Vertical Cross Section)
MIDDLE VERTICAL X-SECTION
EVENTS BETWEEN 39° 29.5' N AND INCLUDING 39°26.0' N
■si
Q-
UJ
O
10
DISTfiNCElKM)
10 15
30'
' ' ' ' ^ -it
^
q: <
I I
^
/
5-
25
M^I.O
Figure 65- Oroville Earthquake Hypocenters, 1976-May 31, 1978 (Middle Vertical
Cross Section)
130
SOUTH VERTICAL X-SECTION
EVENTS SOUTH OF 39° 26.0' N
DISTfiNCE(KM)
30'
5^
-1 , 1 r-^, 1 1 . 1 1 1 r— . 1 1 1— JT F*— ''K
+-H-X ^+ ^
-I 1 1 r
10
+ -^-
A
M^I.O
Figure 66. Oroville Earthquake Hypocenters, 1976-May 31. 1978 (South Vertical
Cross Section)
MIDDLE VERTICAL X-SECTION
EVENTS BETWEEN 39*'29.5'N AND INCLUDING 39*'26.0'N
DISTANCE (KM)
I
t 10
Q_
LiJ
a
M=I.O
Figure 67- Oroville Earthquake Hypocenters. August 2, 1975-December 31. 1975
(Middle Vertical Cross Section)
•
•
1
1
s
JUN.
OROVILLE SEQUENCE
_
MAT
•
•
•
NUMBER OF AFTER SHOCKS /MONTH
-
APR 1
WATER SURFACE ELEVATION
MAR
FEB
•
»
JAN
.
DEC
NOV
OCT
.
SEP
AUG.
•
JUL K
■
•
•
<
JUN
MAr.
.
APR
.
MAR.
FEB.
_
'—1
JAN
•
1
DEC
NOV
OCT
•
•
r
SEP
AUG
•
JUL «
•
•
-
JUN ~
MAY
•
APR
•
•
MAR
FEB
•
•
JAN
DEC
•
•
•
•
?
NUMBER Of AFTER SHOCKS - 5600
NOV
OCT „
SEP 2
1 1
AUG
i '^
si
O
o
O C
o c
o 2
S '^
o
o
o
LAKE OROVILLE WATER
SURFACE ELEVATION
NUMBER OF AFTER SHOCKS/MONTH
Figure 68.
(August
Oroville Sequence, Number of Aftershocks/Month, Water Surface Elevat
1975-June 1978 )
ion,
132
TABLE 3. EARTHQUAKE EPICENTERS, JUNE 1975-DECEMBER 1975
"ITMIN 15,0 KMS OF OROvILLE
/1/75-1J/31/75
LtTITUOE LONGITUDE
AG 0 OUAQR
75/ 6/2B
75/ 6/je
75/ «/je
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ I
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/
75/ 8/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 8/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ 1
75/ 9/ I
75/ 8/ 1
75/ 9/ I
75/ 9/ 1
75/ 9/ 1
75/ 8/ 1
75/ 8/ 1
75/ 8/ 1
75/ 8/ 1
«I19|S3,*
6139140.6
U116ll9.f
20i|01»0.0
18119116.1
61111 2.«
10139152. •
4117137.4
151*5137.6
161j7ll7.t
17I26149.9
18117122.5
19l351t3.0
201201 4.5
2DI20I12.6
20125112.6
20129112.6
20132139.6
211 91 6.«
211)0115.6
21111132.1
21116123.6
2111912*. 5
211201 7.6
21121150.5
21125158.8
21129123.9
21139159.*
2115*135.5
2115811*. 1
221111 *.5
2211*155.6
221151*2.5
39.tS2
39.*70
39. *5*
39.«39
39.««1
39.**1
39.**1
39,»*7
39.**5
39. «3*
39.*63
39.*63
39. *2*
39,tt3
39.**e
39.*78
39.«*3
39.*10
39.**0
39.*38
39.*36
39.*55
39.«79
39.*57
39.*S3
39.*16
39.*35
39.*33
39.**5
39.*90
39.«*7
39.453
39.*5o
121.538
121.5*0
121.5*4
121.540
121.5**
121.538
121.536
121.516
121.5*2
121.560
121.525
121.5*2
121.5*7
121.5*3
121.577
121.539
121.53*
121.534
121.534
121.534
121.513
121,513
121,542
121.517
121.498
121.501
121.501
121.541
121.551
121.512
121.542
121,516
121,470
121.541
121.5*6
121,509
121.551
121.529
121.555
121.536
121,509
121.512
121.530
121.571
121.516
121.502
121.52*
121.580
2.1 C PALERMO
2.6 D PALERMO
1.9 C PALERMO
1.0 C PALERMO
2.2 B PALERMO
2.8 C PALERMO
2,5 C PALERMO
2.1 C PALERMO
2.5 C PALERMO
3.6 B PALERMO
4.7 8 PALERMO
3.0 B PALERMO
2.2 C PALERMO
2.2 C PALERMO
4.5 B PALERMO
5.7 B PALERMO
4.7 B PALERMO
4.6 B PALERMO
3.0 B PALERMO
3.5 B PALERMO
2.5 B PALERMO
2.5 C PALERMO
2.5 C BANGOR
3.0 B PALERMO
3.8 B PALERMO
2.5 D PALERMO
2.6 B PALERMO
3.0 B PALERMO
2.6 B PALERMO
2.8 6 PALERMO
2.8 0 BANGOR
3.2 B PALERMO
2.2 C PALERMO
2,8 B PALERMO
4.1 C PALERMO
3.3 B PALERMO
3.6 B PALERMO
2.7 9 PALERMO
2.2 0 PALERMO
2.0 B PALERMO
3.4 B PALERMO
2.0 C PALERMO
2.5 A PALERMO
3.1 9 PALERMO
2.1 0 PALERMO
1.6 D PALERMO
2.3
2.3
2.3
3i2
5.T
75/ 8/
75/ 8/
75/ 8/
75/ 8/ 1
75/ 9/ 1
75/ 9/ 1
75/ 8/ 1
75/ 9/ 1
75/ 8/ 1
75/ 8/ 2
75/ 8/ 2
75/ 8/ 2
75/ 9/ 2
75/ 9/ 2
75/ 8/ 2
75/ 9/ 2
75/ 9/ 2
75/ 8/ 2
75/ 9/ 2
75/ 8/ 2
75/ 9/ 2
75/ 8/ 2
75/ 8/ 2
75/ 8/ 2
75/ 8/ 2
75/ 8/ 2
75/ 8/ 2
75/ 9/ 2
75/ 8/ 2
75/ 9/ 2
75/ 9/ 2
221231*3.6
221261 *.*
22136115.8
22150120.3
22I52IS6.6
231 4112.6
23li0l»3.6
23114141.4
23131132.6
231*4140.8
23150153.5
231511*9.6
gi 2I»».9
01 3132,2
01 91 59, 9
0113129,1
0123152,9
01351 4,6
01391 3,0
0152148,3
0158155,8
1131129,6
1141137,0
1144112.4
21271 4,9
2131150,7
2139149.1
3115121.2
31421 7,9
3151134,7
41 9113.4
41191 6.1
*1231I3,7
tl*3l35.6
*1*512*.3
51331 5.6
51*7112.5
51*8138.*
5157151.4
6130113.1
6131156.9
9130133.1
101 7155.6
10111153.5
10148159.9
11151121.5
11151150.6
9.431
9.436
9.435
9.425 121.526
9.436 121.508
121.486
121.503
121.551
121,504
121,550
121,549
121,541
121.533
121.545
121.50*
121. *79
121.558
121.50*
121.512
121.517
121.501
121.5*7
121.528
121,550
121.510
121.55*
121.529
121.503
121.515
121.509
121. 479
121.517
121. *29
121.521
121.561
121.57*
121. *89
121,503
121.551
121.599
121.528
121.505
121. *99
121.502
121. t95
121.546
121.525
121.495
438
.426
9.473
7
3.2
PALERMO
1
9
2.5
2.3
2.7
2.6
PALERMO
BANGOR
PALERMO
PALERMO
8
2.5
2.5
PALERMO
PALERMO
9
2.0
OROVILLE
7
2.5
3.4
PALERMO
PALERMO
2.4
PALERMO
2.2
PALERMO
5
2.5
2.4
BANGOR
PALERMO
4
2,3
PALERMO
i
1
2,6
2.0
PALERMO
PALERMO
i
2,6
PALERMO
1
2.2
3.9
PALERMO
OROVILLE
q
2.6
PALERMO
s
2.3
PALERMO
2.3
PALERMO
a
2.2
PALERMO
I
1
2.0
2.3
PALERMO
PALERMO
!
2.3
PALERMO
2.8
BANGOR
2.3
PALERMO
2
2.2
BANOOR
2.0
PALERMO
T
2,0
2.0
0
0
PALERMO
PALERMO
7
2.9
B
BANGOR
7
2.^
B
PALERMO
3
2,2
D
PALERMO
i
2.0
D
PALERMO
2.2
C
PALERMO
2
2,2
c
PALERMO
5
2.0
c
BANGOR
5
3.2
B
PALERMO
2,2
C
BANGOR
7
2.8
3.1
e
PALERMO
PALERMO
:
1
3.3
2.0
B
D
BANOOR
PALERMO
3.4
B
PALERMO
2t3
*.3
2.7
S.3
3.0
i.t
2*0
2.«
2.4
Sit
2.7
2.3
9.3
3.2
s.e
2.T
6.9
*.9
133
TABLE 3. EARTHQUAKE EPICENTERS, JUNE 1 975-DECEMBER 1975 (Continued)
PTHQUaKES MTHIN 15. D K^^S OF QPOjILLE MAJN ShOCK b/1/75-12/31/75
TITUDE LONGITUDE Dr
AC Q QUADRANGLE
75/ 1/ 2 t »4 38 5 J9.»2» 121.504 6.3 3.J B PALEBMO
;;, ly I 1 It 39 3 39!»35 Ul.50» 5.7 2-2 B P4LERM0
;i \V,lt'M\\ ll-Ml ill:*?. 1.2 2.0 6 BJNOO«
•»ey a/ 3 I>ii4l49.5 30.451 121.502 5.0 2.2 B P«LEI1H0
«/ ?/ I 5 O " ! " tis 2 iSs 4.5 2.0 C PALERMO
45 IV.IV. 111:15! ?:i !:i ? S?
75/ '/ I 17.I4.29.1 39.482 121.489 6.5 4.3 S B4N00O
75/ 8/ 2 1714)124,0 39,4»5 121.491 6.1 4.0 B B4N80B
is;! lliiiiU:? U:U! lll:ni 1:5 I:? I «o
?i; s; i isuii^s:? i?:tl? ll!:^? ^: : S
75/ s/ ? 2CI59I55.6 39,449 121.493 B.7 5.2 6 B4NG0B
3,.4 = » i^,.. = P .." -- " eANGOB
39.439 121.495 2.8 2.3 S B4N60B J*^
21133156.3
221351 8.5 39.415 121.463
231 0123.8 -- "" ■-■ ■"
8AN60B 5.3
BANGOR *•*
,o',»» ,21 497 i.7 2.2 e BANGOP
mum lis iiis HI liiiis lii
75/ »/ 3 21471 8.6 39.482 121.514 7.1 4.1 A PALEPMO ♦■»
^i;?;^ '.i!; : :4l 111:5" ::9 1:3 b paleb«o j.t
1 l!n:l IV:X 111:1?^ ^:? i:J I -"- H
; ?!12:I 1?:UI lilitH ^:? 1:5 i i-?§S :
:5;!t:I i?:t^^ 111:1^8 I:? I:S ? ^t^S:? :
ii ? I lii?!'!?:: n::f^ 1I1::?J l:? I:5 S i» :
51; 1; ? li\^^ IVMl WVMl r.8 I" B Zlll :
^1 2 1?::!5 1I{:!^J I:^ 1:1 I ^ii^i^ :
: b:;n:2 n::il lll:llt ?:5 ?:l S SS :
;ii;: 11!,?:;;:! n:tsi 1I1:U! V.l l:? I bI^^oS" ?:J
75/ 8/ 5 2128157.1
121:497 6:2 3.3 « bANOOR '•'
n^hl liliilSii i2:JU m-.m J:I 2:1 1 ?itl5B§ |:|
75/ 8/ 5 151 3155.7 39.422 121.501 6.7 1.6 4 PALERMO 3'5
75/8/5 20.44124.4 39.429 121.537 7.9 3.2 B PALERMO 1-3
75/ 8/ I 23 57 lui 39 496 121.534 9.3 2.8 B PALERMO
121.555
75/ 8/ 6 3 50129:5 39:495 121.540 «.T 4.7 A PALERMO ---
::. :. ! : =,»n., «..99 121.555 s.i 2.8 b palermo '•'
121.529 S.2 2.4 A PALERMO 5.7
121.531 ».0 2.0 A PALERMO 5.T
121.491 5.3 1.9 B BANGOR »•*
121.541 9.0 2.7 B PALERMO 5.J
121.533 B.S 1.9 A OROVILLE '•»
75/ 8/ 6 10135122.8 39.433 121.505 6.1 1.8 A PALERMO | 7
75/ 8/ 6 131 3128.3 39.502 121.533 9.3 2.9 A OROVILLE »•'
75/ 8/ 6 131 9130.9 39.503 121.523 9.0 2.5 A OROVILLE »•»
75/ 8/ 6 6125147.2 39.406 121.487 5.7 3.1 A BANGOR J.T
75/ 8/ 6 16141.51.8 39.495 121.537 9.1 3.6 A PALERMO »»0
75/ 8/ 6 19142148.3 39.504 121.543 7.7 2.8 B OROVILLE J'l
75/ 1/ t 2? ol32:e 39:410 121.522 9.4 3.0 A PALERMO J-J
75/ 8/ 7 5.15.48.3 39.400 121.489 7.8 2.3 8 BANOOR »•«
7I/ 9/ 7 14 20.45 1 39.509 121.541 9.8 2.9 A OROVILLE 7.6
75/ 8/ 7 19.f2l55.8 39.504 121.534 6.2 2.4 A OROVILLE J.O
75/ 8/ 7 26l!5.39:i 39,;il 121.482 4.3 2.6 , 9ANGOR »•»
75/ 8/ 7 20.31.20.0 39.503 121.531 9.2 3.1 A OROVILLE *•»
75/ 8/ 9 0 53.22.9 39.415 121,526 7.9 2.3 B PALERMO 3.0
75/ ./ 9 7 0 50:0 39,496 121.524 8,5 4.9 8 PALERMO »•«
7I; S/ I nls'ilS:? IV.hl UiMz ?:6 3.2 B PALER«0 7.
75/ 9/ 8 15.501 8.4 39.468 121.486 6.1 2.6 B BANOOR J.l
75/ 6/ 8 19. 3.27.3 39.410 121.498 7.« 3.1 A BANOOR *••
75/ a/ 9 7.38147.1 39.406 121.499 6.0 3.0 A BANOOR ♦•»
75/ 8/ 9 12l?ll35:2 ^IslO 121.518 9:2 2.4 B OROVILLE 7.i
75/ 8/ 9 20145131.0 39,413 121.489 5.1 2.6 4 BANOOR »•»
"/ S/.i U.35.25.; 39.406 .21.498 4,3 2.2 fl flANGOR |.»
7!/ 8/10 21.25.44,8 39,439 121,510 .1 2.1 C PALERMO Z-j
75/ 8/11 2.40.14.5 39.4*0 121.46T J.O 3.0 4 BANGOR »•!
75/ 8/11 6111.36.3 39,459 121,484 5.0 4.3 A BANGOR •• '
75/ 8/11 6.34.50.8 39,423 121.509 5.* 2.8 A RAL"MO |;»
75/ 8/11 7141138.8 39,413 121.488 5.6 2.7 A BAN60R »•«
A, 1/ 15 U 5 5 39 M6 121,536 9.0 3.6 A OROVILLE 7.2
75/ 8/12 1. 5.21.4 39.411 121,492 4.5 2.3 A BANOOR *•»
»/ IM ll29, 2.2 39:441 121.486 4.0 2.8 B BANGOR ».l
75/ 8/1 2 11145.21,4 39,408 121,498 3.7 2.1 A BANGOR •••
75/ S/ll 1 56 11 9 39 ;59 12 .534 U.O 3.0 B "LERMO «•»
A, IM 16.42. 8.7 39.519 121,529 8.4 2.9 B OROVILLE ».»
75/ 8/12 19.45.12.1 39.439 [21.510 6.6 2.7 4 PALERMO 2»0
75/ A/ifc «i 4111.4 39.415 121.496 4.5 2.2 B BANOOR *••
"/ S/16 lUel 9:2 59.t71 121.538 9.1 4.0 A PALERMO 3.3
134
TABLE 3. EARTHQUAKE EPICENTERS, JUNE 1 975-DECEMBER 1975 (Continued)
E«»TmQJ«KFS •ITHIrj Ib.o KMS Of OrtOvRLE >'4IN ShOC« 6/1/75-1J/31
YU »0 r)> HR "N SEC L«'ITUOE LONGITUDE DfPIH
75/ 8/16
75/ 8/16
75/ 8/16
75/ 8/18
75/ 8/20
75/ 8/Jl
75/ 8/?3
75/ 8/2*
75/ 8/2«
75/ 8/25
75/ 8/25
75/ 8'26
75/ 8/29
75/ 8/2?
75/ 8/2«
75/ S/31
75/ 9/ 3
75/ 9/ »
75/ 9/ »
75/ 9/ 4
75/ 9/ 5
75/ 9/ 7
75/ 9/ 7
75/ 9/ 7
75/ 9/28 ^
75/ 9/28 ^
75/ 9/28 1"
75/ 9/28 21
75/ 9/30 17
75/10/ 2 21
75/10/ 2 22
75/10/ 2 22
75/10/ 3 1
75/10/ 3 ?
2312*. 3
01 8.»
9129.8
56153.2
30U6.3
0138.8
31153.0
10137.2
55157.2
35111.0
39lt3.9
2TC43.3
«5i3i.e
>eii2.5
6125.3
3211».»
20153.9
171 1.9
39125.6
31»3.8
1136.9
371 5.0
42139.0
10154.3
31130.1
361U.9
k9l58.5
>51 9.0
.6123.1
22115.7
51 2.0
25137.4
59150.6
7114.7
3136.3
9137.0
51111.6
6133.9
42125.6
39.502
39.495
39.499
39.406
39.413
39.424
39.496
39.485
39.503
39.484
39.472
39.411
39.476
39.464
39.462
39.406
39.498
39.412
39.506
39.411
39.406
39,406
39.414
39.405
39.559
39.427
39.412
39.519
39.517
39.521
39.516
39.511
39.395
39.409
39.503
39.411
39.402
39.434
39.425
39.410
39.424
39.418
39.392
39.504
39.513
39.525
39.524
39.516
39.527
39.518
39.515
39.509
39,520
39.515
39.506
39.523
39.502
39.415
39.529
39.529
39.441
39.504
39.514
39.406
39.464
39.466
39.456
39.416
39.411
39.511
39.496
39.410
121.513
121.506
121.512
121.506
121.500
121.472
121.494
121.498
121.492
121.496
121.519
121.545
121,511
121.529
121.526
121.500
121.487
121.543
121.518
121.497
121.515
121.516
121.493
121.514
121.531
121.563
121.489
121.526
121.524
121.526
121.522
121.491
121.516
121.521
121.506
121.500
121.516
121.506
121.495
121.526
121.527
121.509
121.515
121.505
121.501
121.495
121.492
121.529
121.529
121.525
121.524
121.522
121.521
121.525
121.526
121.525
121.525
121.516
121.527
121.526
121.506
121.520
121.524
121,512
121.518
121.505
121.524
121,490
121,496
121.491
121.551
121.541
121.490
121.500
121.532
HiO
°
0UA09ANGLE
3.2
OBOVILLE
2.6
PALERHO
2.8
PALE9M0
2.9
PALERMO
2.9
PALERMO
2.6
3.1
BAN30R
SANOOR
3.3
BANGOR
2.1
orovillE dam
3.2
BANGOR
2.0
2.7
2.9
PALERMO
PALERMO
PALERMO
2.9
2.9
PALERMO
PALERMO
2.6
BANGOR
2.2
3.0
BANGOR
PALERMO
2.1
2,0
OROVILLE
BANGOR
3,2
2.9
PALERMO
PALERMO
2.5
BANGOR
2.5
PALERMO
2.3
C
OROVILLE
2.0
C
PALERMO
2.0
A
BANGOR
3.2
B
OROVILLE
2.5
B
OROVILLE
3.5
2.3
B
B
OROVILLE
OROVILLE
3.5
e
OROVILLE DAM
1.9
C
PALERMO
2.7
e
PALERMO
2.0
1.6
2.4
2.4
c
B
OROVILLE
BANGOR
PALERMO
PALERMO
2.0
4.0
6
B
BANGOR
PALERMO
1.7
B
PALERMO
2.6
1.9
e
PALERMO
PALERMO
3.2
e
PALERMO
1.9
2.1
B
PALERMO
BANGOR
2.5
6
OROVILLE 0A1
4.6
2.9
1.3
1.5
1.6
3.0
3,0
B
6
OROVILLE
OROVILLE
OROVILLE
OROVILLE
OROVILLE
OROVILLE
OROVILLE
2.6
B
OROVILLE
2.0
1.5
J
OROVILLE
OROVILLE
1.6
2.0
1.7
e
OROVILLE
OROVILLE
OROVILLE
2.2
1.6
3.4
2.4
1.3
1-3
1.9
2.8
2.8
2,0
1,6
B
8
e
8
c
e
e
B
6
PALERMO
OROVILLE
OROVILLE
PALERMO
OROVILLE
OROVILLE
PALERMO
BANOOR
BANGOR
BANGOR
PALERMO
2,2
B
PALERMO
1,5
1.7
e
OROVILLE DAM
PALERMO
2.6
B
PALERMO
*|4
5.T
3.i
3.4
4.4
4.6
4.2
4.2
4.6
8.6
6.4
8.9
75/10/ 4
12128139.9
39.513
121.519 n.
75/10/ 6
9154142.5
39.411
121.548 1(.
75/10/10
7144147.4
39.462
121.492 3.
75/10/11
23154156.6
39.522
121.518 9.
75/10/12
4140153,6
39.467
121.485 i.
75/10/12
151 5135.2
39.507
121.527 7,
75/10/12
23124117.4
39.400
121.511 4.
75/10/13
14156137.0
39.492
121.511 3.
75/10/13
161 6151.2
39.492
121.515 5.
75/10/13
211301 7.1
39.428
121.466 2.
75/10/14
2144158.5
39.506
121.527 4.
75/10/14
91 11 5.7
39.406
121.512 ?.
75/10/14
211321 6.4
39,471
121.509
75/10/16
3120146.9
39.400
121.466 |.
75/10/18
13159142.2
39.408
121.509 7.
75/10/20
141411 .7
39.512
121.522 5.
75/10/20
151221 5.7
39.506
121.525 ?.
75/10/21
13126125,0
39.414
121.512 3.
75/10/23
201 7144.5
39.475
121.534 4.
75/10/26
6123119.3
39.414
121.496
75/10/27
211 2144.4
39.506
121.517 3.
75/10/28
3141116.0
39.496
121.510 3.
75/10/26
5113146.0
39.525
121.534 A,
OROVILLE
PALERMO
BANGOR
OROVILLE
BANGOR
OROVILlE
PALERMO
PALERMO
PALERMO
BANGOR
OROVILLE
P*LErmo
PALERMO
BANGOR
PALERMO
OROVILLE
OROVILLE
PALERMO
PALERMO
BANGOR
OROVILLE
PALERMO
OROVILLE
135
TABLE 3. EARTHQUAKE EPICENTERS, JUNE 1 975-DECEMBER 1975 (Continued)
TMOUIRES »ITHIN 15. g KMS OF 0«OuILLE >f«IN SHOCK
ATITUOE LONGITUDE OfP
AG 0 QUAQtJANGLE
75/10/31
75/11/ 1
75/11/ 3
75/11/ 3
75/11/ ♦
75/11/ 5
75/11/ 5
75/11/ 5
75/11/ 7
T5/11/ e
75/11/ 9
75/11/
75/11/
75/11/
75/11/
75/11/
75/11/
75/11/
75/11/
75/11/
75/11/. _
75/11/20
75/ll/?3
75/11/33
75/11/?*
75/11/25
75/11/26
75/11/26
75/11/26
75/11/26
75/11/27
75/11/30
75/12/ 1
75/12/ 1
75/12/ 3
75/12/ 3
75/12/ 3
75/12/ 5
75/12/ 6
75/12/ 7
75/12/ i>
75/12/10
75/12/11
75/12/12
75/12/13
75/12/19
75/12/20
75/12/21
75/12/23
75/12/23
75/12/26
51371»7.0
19l30>3e.e
231181 6.»
23l5ei«2.5
31351 1.6
31*51 8.*
* 122 13*. 3
131*1116.''
51 0135.1
1911711*. 6
81»71 6.5
131101*3.1
12136116. e
7132153.5
211
7.1
,1139.6
1113128.5
121 812*. 2
12151153.3
13153153.7
15159123.7
23159120.6
10123120.9
7150129.5
23126127.3
1133112.0
7112113.1
9.5
8152132.*
13133115.1
215*1*3. »
2155119.6
71 »120M
111*12*. 8
121. *93
121. »95
121.509
121.507
121.517
121. *92
121.521
121. *89
121.517
121. »6*
121. *91
121.505
121. *B7
121. *90
121.501
121. *6*
121.506
121. *92
121.526
121. »87
121.472
121. *8*
121.500
121. *90
121.521
121.500
121.521
121.496
121. *88
121. »e5
121.512
121. *93
39.*72 121. *e3
39,»04 121.496
39.403 121.500
39.42* 121. »91
39.398 121. *65
39.396 121.475
39.411 121.471
39.408 121.501
39.507 121.48*
39.513 121.517
39.497 121.524
39.507 121.541
39.457 121.510
39.536 121.494
39. 4*7 121.503
39. *5* 121.532
39.507 121.523
121. *75
121.516
121.473
121.511
39.502
39.427
39.511
BANGOR
PALERMO
BANGOR
BANGOR
PALERMO
BANGOR
OROVILLE
BANGOR
PALERMO
B BANGOR
A PALERMO
C BANGOR
B PALERMO
A BANGOR
B PALERMO
B BANGOR
A BANGOR
B bANGOR
A PALERMO
C BANGOR
B PALERMO
C PALERMO
B OROVILLE
B BANGOR
B BANGOR
B OROVILLE DAM
B PALERMO
A OROVILLE DAM
B BANGOR
C BANGOR
B PALERMO
A BANGOR
B BANGOR
C BANGOR
.E OAM
39,523
39.431
39.41*
75/12/27 51**150.3 39.*10 121.501
BANGOR
PALER»
OROVIL
OROVILLE
PALERMO
OROVILLE
PALERMO
OROVILLE DA
PALERMO
PALERMO
OROVILLE
BANGOR
OROVILLE
BANGOR
PALERMO
4. a
*.9
*>6
3>T
S.3
S.2
»•*
S.2
T.O
3.9
3.9
T.2
S.5
*.9
«.3
*.5
3.2
6.S
«.2
».T
*.a
4.S
s.*
2.6
4.9
T.2
A. 9
8.6
5.S
5.2
136
TABLE k. EARTHQUAKE EPICENTERS, JANUARY 1 976-MAY I978
EAKTmUUIKES ■ITmIU 15. J KMS OF OROvILLE M«IN ShOCK 1/1/76-5/31/78
YB MD 01
HR UN SEC
LATITUDE LONGITUDE
oep
76/ ]/ 1
16:58:3'. 3
39.421
2
.494
76/ 1/ ?
10:22: ''.7
39.454
2
.481
76/ 1/ 5
14:35:38.5
39.432
2
.514
76/ 1/ «
10:4^:32.6
39.410
2
.472
76/ 1/ i.
15:41137.7
39.510
2
.528
76/ 1/ 4
15:so: 4.4
39.498
2
.508
1 1.
76/ 1/ iJ
17:54:26.0
39.488
2
.487
76/ 1/10
2l: 5:23.7
39.394
2
.479
76/ 1/15
23:3l:»5.3
39.521
2
.473
76/ 1/17
7: 15:20.0
39.424
2
.467
76/ 1/18
0:37l22.9
39.417
2
.484
76/ 1/23
13:i3:i8.8
39.413
2
.484
76/ l/?6
2: l:«2.6
39.420
i
,466
76/ 1/?«
19:401 .7
39.416
2
.479
76/ i/?6
21= 8:i4.o
39.437
2
.468
76/ 1/J8
3:5211''. 5
39.405
2
.517
76/ i/je
23:41:3*. 9
39.39*
2
.502
76/ J/ ,
IB: 7:56.7
39.526
2
.557
76/ ?/ ?
19:ii:5b,4
39.441
2
.486
76/ ?/ ?
21:43|53.7
39.460
2
.503
loi
76/ ?/ 9
9:56:47.9
39.485
2
.»9o
76/ ?/ t)
ic; 9:33.5
39.485
2
,485
76/ ?/ 9
11: 6:46.6
39.484
2
.495
76/ ?/ ■)
13:33: 5.6
39.503
2
.523
76/ ?/ W
13:42139.3
39.492
2
.475
76/ ?/ «»
13:57:49.2
39,495
2
.523
z..
76/ ?/!<>
lu: 3: '.»
39.497
2
.513
6,
76/ ?/?3
9:59:33.4
39.481
2
.498
76/ 3/ 6
12: 6:30.4
39,446
2
.499
u ,
76/ 3/12
5:38:26.8
39.480
2
.501
76/ 3/15
6:52:31.7
39.470
2
,466
1.
76/ 3/lS
7;i4119.5
39.409
2
.503
1 .
76/ 3/19
2:i4:56.3
39.541
2
,509
76/ 3/?0
Ij: 9:42.1
39.409
2
.470
76/ 3/21
14: 3:26.1
39.397
2
.539
2,
76/ 3/27
15:51:42.7
39.500
2
.484
76/ J/24
8:»2: 5.6
39.499
2
.525
8,
76/ «/ 3
22:49:32.2
39,414
2
.480
7,
76/ u/ 4
is: 4:31.6
39.415
2
.489
2.
76/ J,/ ^
■5:41:22.4
39.491
2
.5o7
76/ 4/ 1 2
7:43: 4.5
39.410
2
.415
q.
76/ ./16
17:ii:5i..7
39.501
2
.497
3.
17:21:36.9
39.498
2
.480
76/ <./3„
20:5l:39.2
39.428
2
.466
76/ ^/ 7
7:41143.4
39.465
2
.469
76/ S/ 7
13:48: 3.3
39.419
2
.491
3.
76/ './li
1: 7118.1
39.420
2
.490
2.
76/ 5/15
15:36: 7.5
39.418
2
.484
4.
76/ 5/17
17:13: 6.1
39.447
2
.491
3.
76/ s/ie
9:46:46. «
39.4'U
2
.465
76/ 5/19
1 :10: 3.1
39.514
2
.486
3.
76/ 5/20
7:27:34.5
39.489
2
.491
1.
76/ 5/21
18:41:42.7
39,409
2
.514
76/ 5/26
3:55:25.3
39.495
2
.527
=1.
76/ 5/31
2:36: 1.1
39.507
2
.523
3.
76/ 5/31
51301 2.4
39.412
2
.477
76/ 5/31
6:31143.0
39.509
2
.518
fi.
76/ 6/ 6
12:i4:16.7
39.420
2
.489
7.
76/ 6/14
6:37:28.2
39.473
2
.529
».
76/ 6/14
18:36: 6.2
39,525
2
.525
6.
76/ 6/14
23:30!2''-2
39.473
2
.538
8.
76/ 6/l«
23:51 :54.6
39.470
2
.532
7,
76/ 6/25
19:12:22.2
39.413
2
.465
3,
76/ 6/26
6: 3: .5
39.407
2
.490
4.
76/ 6/29
7: 3156.4
39.525
2
.528
7,
76/ 7/ 1
0:59:54.4
39.511
2
.492
6.
76/ 7/ 6
3155:17.5
39.409
2
.527
7,
76/ 7/ 6
7:59:33.9
39.413
2
.519
6.
76/ 7/ 7
3:43i«s.i
39.544
2
.513
6.
76/ 7/11
23:19:20.3
39.403
2
.489
1,
76/ 7/20
5:33: 9,7
39.404
2
.484
3.
76/ 7/23
16:31=15.7
39.512
2
.525
1".
76/ 7/24
12:57: 2.!
39.482
2
.499
s.
76/ 7/31,
17:27:41.5
39.488
2
,528
1 1.
76/ n/16
15:11157.9
39.411
2
.494
3.
76/ B/16
18:53:33.7
39.409
2
.501
3.
76/ 6/16
23:13:41.9
39.403
2
.506
3.
76/ n/19
5143149.5
39.539
2
.507
5.
76/ S/l9
8115: 4,5
39.4SB
2
.473
5.
76/ 5/24
7:i5i«e,5
39.422
2
.497
J ,
76/ e/31
19129:35.2
39.508
2
.543
9.
76/ 9/16
22112:47.9
39,499
2
.492
76/10/21
6l36:U'5
39.389
2
.480
H'
76/10/22
13:51:11.5
39.407
2
.483
4,
76/11/10
8:14:57.2
39.412
2
.491
76/11/23
12:58: 6.4
39.469
2
.488
76/12/15
1 :32i32.2
39.408
2
.496
4 ,
76/12/25
15:58:24.4
39.495
2
.488
76/12/29
3: 3:55.7
39.416
2
.478
77/ 1/ 9
23:24:40,3
39.487
2
.499
4 .
77/ 1/ 9
23127144,1
39.491
12
1.509
5
77/ 1/12
3130113.7
39.413
2
.493
2,
77/ 1/23
11: 2115.0
39,401
2
.486
2.
77/ 1/30
6135:24.9
39.440
2
.491
4,
77/ 3/ 2
17:55:32-6
39.407
39.426
2
.493
4'
77/ 3/12
0:46il5.5
2
.490
''.
2.1
(J
8
QUADRANGLE
8ANGGR
1.2
C
BANGOR
1.9
B
PALERMO
1.1
B
BANGOR
1.7
B
OROVILLE
1.2
C
PALERMO
2.1
B
BANGOR
1.2
C
BANGOR
1.9
8
OROVILLE DA
2.8
B
BANGOR
2.9
B
BANGOR
1.6
B
BANGOR
2.5
6
BANGOR
3.2
B
BANGOR
1*4
B
BANGOR
2.3
B
p*lErmo
2.3
B
PALERMO
2.2
C
OROVILLE
1.7
C
BANGOR
1.3
0
PALERMO
1-i
c
BANGOR
\.U
c
BANGOR
1.8
B
BANGOR
2.5
B
OROVILLE
1.0
B
BANGOR
1.9
C
PALERMO
l.C
B
PALERMO
1.0
1 .1
C
B
BANGOR
BANGOR
1.0
1.0
C
B
PALERMO
BANGOR
2.9
B
PALERMO
1.7
B
OROVILLE
2.0
B
BANGOR
1.4
B
PALERMO
2.5
B
OROVILLE DA
2.2
A
PALERMO
1.2
S
BANGOR
2.2
B
BANGOR
1.2
B
PALERMO
1.2
[)
BANGOR
2.9
B
OROVILLE DA
1.2
2.1
B
BANGOR
BANGOR
2.4
1.7
C
8
BANGOR
BANGOR
1.6
B
BANGOR
2.2
B
BANGOR
1.1
B
BANGOR
2.5
B
BANGOR
1.8
B
OROVILLE DA
2.3
1.3
6
C
BANGOR
PALERMO
2.4
B
PALERMO
2.6
B
OHOVILLE
2.5
b
BANGOR
2.4
B
OROVILLE
1.2
B
BANGOR
2-5
B
PALERMO
2.1
e
OROvILLE
3.4
B
PALERMO
2.1
e
PALERMO
2.6
B
BANGOR
2.4
B
BANGOR
2.0
A
OROVILLE
2.6
4.1
4
OROVILLE DA
PALERMO
2.2
A
PALERMO
2.0
B
OROVILLE
2.6
9
BANGOR
2.3
C
b'ngor
1.2
C
OROVILLE
1.8
1.0
B
B
BANGOR
PALERMO
2.5
1.0
8
BANGOR
PALERMO
2.9
C
PALERMO
1.4
B
OROVILLE
2.9
A
BANGOR
2.6
B
BANGOR
2.7
B
OROVILLE
1.1
D
BANGOR
2-3
B
BANGOR
2.9
e
BANGOR
1.0
c
BANGOR
1.9
c
BANGOR
1.5
B
BANGOR
2.0
B
BANGOR
2.9
B
BANGOR
3.4
2.3
8
B
BANGOR
PALERMO
2.5
A
BANGOR
1.0
B
BANGOR
2.8
A
BANGOR
2.6
8
BANGOR
1.2
e
BANGOR
4.1
4.8
2.0
6.3
7.7
6.7
6.6
7.1
10.3
6.1
5.1
5.3
6,3
5.5
5^7
4.3
5.7
9.6
4.2
3.5
i'i
6.5
5.8
6.9
7.6
6.0
6.5
5.4
3.1
5.1
6.7
*.S
11. '3
6.6
4.9
7.9
7.8
4.4
6.1
4.4
4.4
5.0
3.7
6.8
9.1
6.5
4.0
6.0
7.3
5.9
7.6
4.6
3-6
9.3
3.6
3.2
6.7
5.3
9.4
8,6
3.6
3'.*
11.6
5.7
6.0
7.9
5.5
5.2
4.8
4.5
4.8
11.1
5.6
3.8
7^5
7.4
7.;4
5.8
4.9
5.0
4.9
7.3
5;5
6^0
6.0
4.7
6.1
3.7
137
TABLE h. EARTHQUAKE EPICENTERS, JANUARY 1976-MAY 1978 (Continued)
KES »IThIN li.O KMS OF OHOVILUE MAIN ShOCK 1/1/76-5/31/78
aTITUOE LONGITUDE OfPTH
AG Q UUADRANGLE
77/ 3/1-.
2?
37121.7
3V
401
121
77/ 4/15
n
39140.2
39
410
121
77/ »/?7
4
?6:29.2
39
404
121
77/ 4/JB
16
23113.0
39.
416
121
77/ 4/?6
17
45152.1
39
410
121
77/ 5/ »
6
niU.4
39
400
121
77/ 5/ 4
6
15136.3
39
401
121
77/ 5/ 4
6
S91 10.2
39.
400
121
77/ 5/ ^
7
1=53.2
39
399
121
77/ 5/U
16
441 7.3
39
502
121
77/ 5''7
17
18126.9
39
405
121
77/ 5/ IE
17
20122.4
39
461
121
77/ 5/J5
I'l
16156.4
39
417
121
77/ 7/14
0
39156.1
39
516
121
77/ 7/lf.
9
43120.7
39
405
|21
77/ 7/1?
0
57123.6
39
421
121
77/ 7/20
8
461 16.6
3'
427
121
77/ 8/ t>
10
35l28.7
39
4I4
121
77/ S/30
22
57144.3
39
419
121
77/ 9/13
4
78126.5
39
403
121
77/ g/n
6
39149. H
39
403
121
77/10/ 3
18
22136.2
39
442
121
77/in/ie.
10
361 10.2
39
556
121
77/11/10
20
24142.2
39
410
121
77/11/J3
8
261 2.7
39
402
121
77/1?/ t.
14
14157.5
39
4U3
l2l
77/lJ/ 9
4
3111.5
39
403
121
77/1?/ 9
9
391 7.8
39
404
121
77/12/11
8
42'41.9
39
l^l
121
7'/l?/2'
12
331 a.'
3'
121
78/1/4
20
56122.8
3'
410
121
78/ 1/31
22
9157.9
3"'
521
121
76/ 3/ 1
13
55114.7
39
454
121
78/ 3/?^
16
20l30.6
39
467
121
76/ 4/ 2
14
46153.9
39
421
121
7B/ 5/ 6
16
48134. H
39
611
121
76/ 5/P9
20
?7i31.Q
39
40'
121
1.0 B BANGOR
1.9 B BANGOR
2
0
a
BANGOR
1
2
B
BANGOR
2
9
B
BANGOR
2
7
e
BANGOR
3
4
a
BANGOR
1
5
c
BANGOR
2
0
c
c
OROVILLE
BANGOR
7
D
BANGOR
6
B
BANGOR
8
3
6
C
OROUILLE
BANGOR
4
C
BANGOR
4
C
BANGOR
1
0
1
a
BANGOR
PALERMO
2
5
B
BANGOR
2
3
a
BANGOR
2
5
B
PALERMO
0
a
OROVILLE
9
B
BANGOR
2
B
BANGOR
0
B
BANGOR
9
a
PALERMO
9
a
BAmGor
0
1
0
a
c
B
BANGOR
BAnGOR
BANGOR
0
0
0
c
c
c
OROVILLE
PALERMO
BANGOR
0
D
BANGOR
2
BIDWELL
0
B
BANGOR
a>6
4.9
S.7
5.3
5.7
6^4
6.5
6.6
6.7
8.3
5.9
7.0
5.7
8.6
5.6
7.1
5.0
4.6
2.7
8.6
8.3
1.2
13. B
4.6
S.6
6.9
5.1
6.0
5.4
12.1
5.8
10-1
1.6
5.9
9.3
9.0
6.6
138
References
1. Lee, W. H. K, , J. C. Lahr, Hypo 71 (revised). "A Computer Program
for Determining Hypocenter, Magnitude, and First Motion Pattern
of Local Earthquakes." USGS Open File Report 75-311.
2. Lee, W. H. K. , R. E. Bennett and K. L. Meagher (1972). "A Method of
Estimating Magnitude of Local Earthquakes from Signal Duration."
U. S. Geological Survey Open File Report.
3. Hofmann, R. B. , and R. W. Wylie (1964), "Proceedings of the VESIAC
Conference on Seismic Event Magnitude Determination." Institute of
Science and Technology, University of Michigan.
4. Lahr, K. M. , J. C. Lahr, A. G. Sindh, C. G. Bufe and F. W. Winter
(1976), "The August 1975 Oroville Earthquakes." BSSA, 66, 4, p. 1085-
1099.
5. Savage, J. C. , M. Lisowski, W. H. Prescott, and J. P. Church (1977)
"Geodetic Measurements of Deformation Associated with the Oroville,
California Earthquake." JGR, 82,11, p. 1667-1671.
139
CHAPTER IV
VERTICAL AND HORIZONTAL GEODESY
Vertical Crustal Movements
Introduction
Due to the August 1, 1975, Oroville
earthquake (magnitude 5.7, main shock
located about 12 kilometres southwest of
Oroville Dam) , the Department began an
intensive surveying program to reobserve
previously established vertical and hori-
zontal control networks to determine
locations , magnitude of movement , and
trends of the major faulting.
A monitoring network to measure horizon-
tal and vertical movement at Lake Oro-
ville was established in 1967. In April
1968, the horizontal network was remea-
sured, and in late 1968 releveling of
most of the network was completed. In
1969, about half of the level network
was releveled.
Figure 69 shows a plot of the filling
of Lake Oroville to Elevation 274.3
metres (900 feet) starting in 1967 and
the normal cycling of the lake. Also
shown is the effect of the California
Drought; beginning in 1976, Lake Oroville
receded to its lowest water elevation
since filling (198.1 metres (650 feet)
in December 1977) . Between December 1977
and June 1978, the lake refilled to
within a few metres of full .
The location of the Oroville area level
lines (1977) are shown on Figure 70.
The end points of the lines are not
connected on this figure for purposes
of identification.
The following precise surveys were made
in response to the August 1, 1975,
Oroville earthquake:
1975 August - September:
1976 January - April :
1976 September - November:
1977 September - November:
1978 August - September:
Leveling and Horizontal Control .
About half releveled.
All level lines rerun.
All level lines rerun.
About 90 percent of total length to be rerun.
Precise Survey Programs
September 1967. The Lake Oroville Moni-
toring Network was the original program
to monitor the area around Oroville Dam
and Lake Oroville for movement caused by
the filling of the lake. Figure 71 shows
the level net for study of Lake Oroville -
1967.
The program consisted of establishing 106
new bench marks as well as leveling an
additional 139 bench marks for a total
network of 94.15 kilometres (58.5 miles).
The leveling accuracy was Class 1 first-
orderi/, which means the closure error
for each line may not exceed 3.0 milli-
metres (0.010 foot) times the square
root of the distance in kilometres.
The leveling was run from an established
U. S. Coast and Geodetic Survey (USC&GS)
network in and near the City of Oroville.
The leveling was extended easterly and
northerly to diorite rock masses. The
USC&GS established the elevations along
the lines and terminal bench marks and
the Department completed first-order
leveling over the net interior. These
elevations are used as the base refer-
ence elevations.
1/ Classification, Standards of Accuracy, and General Specifications of Geodetic
Control Surveys, U. S. Department of Commerce (February 1974).
141
300
250
900
-800
700
200
-600
500
1967
1968 ' 1969 ■ 1970 ' 1971 1972 1973 1974 1975 1976 1977
Figure 69- Lake Oroville Water Surface Elevation
1978
July - September 1968. Because the funds
allotted to survey the entire 1967 net-
work were inadequate. Line Olive leveling
was omitted (12.1 kilometres, 7.5 miles),
and the Line Bald Rock leveling was
shortened by 9.7 kilometres (6.0 miles).
This leveling was performed using second-
order methods, single run, except where
differences in elevations between bench
marks previously established were in
excess of first-order tolerances, then
reruns were made for confirmation. A
total of 57.6 kilometres (35.8 miles)
were run in one direction between July 1
and September 27.
October - November 1969. Twenty-six kilo-
metres (16 miles) of Class 1 first-order
leveling was conducted during October
and November.
August - September 1975. Because of the
earthquake, 117 kilometres (73 miles)
of Class 1 first-order levels were made
between August 13 and September 12.
January - April 1976. Seventy-five kilo-
metres (47 miles) of Class 1 first-order
levels were made between January 19 and
April 8.
September - November 1976 . One hundred
sixty-two kilometres (101 miles) of
Class 1 first-order leveling was accomp-
lished between September 15 and November
11.
September - November 1977. This Class 1
first-order survey releveled the
September - November 1976 network of 162
kilometres (101 miles) , between Septem-
ber 13 and November 3. The level net,
for study of Lake Oroville - 1977, is
shown on Figure 72.
142
Precise Survey Adjustment
Free Adjustment. Independent free adjust-
ments for each epoch of leveling were
made using the variation-of-parameters
method of least squares. In free adjust-
ments, the net is not constrained to fit
previously established elevations. Only
Bench Mark OM-27, Elevation 540.468 metres
(1773.19 feet), (1967 USC&GS adjustment)
is assumed to be stable at the fixed
elevation, and all other elevations are
adjusted in relation to it. Therefore,
any comparison of the free adjusted
elevation of a bench mark in one epoch
to that of another epoch indicates
apparent movement between two levelings.
MINERS RANCH
FEATHER FALLS
BIDWELL CANYON SADDLE DAM
fN-MINERS RANCH
MISSION OLIVE
CLEVELAND HILL
ORO-BANGOR
AVOCADO
K(LOI«ETRE
Figure 70. Orovi lie Area Level Lines (1977)
143
KILOMCTKE
Figure 71. Precise Level Net for Study of Lake Oroville - 1967
The level net used for the October 1977
adjustment typifies the basic network as
refined to that date (Figure 72) .
Spur Lines. Six main spur lines are
connected to the main net without benefit
of closure back to the net; therefore,
these lines are not adjusted and reflect
only observed elevations. The lines are
Feather Falls, Bidwell, Bald Rock, Rich-
vale, Potter and Line 103. Also, sev-
eral short spur lines are connected to
the net.
Line Feather Falls is the connecting
link between the fixed Bench Mark OM-27
and OM-20 (main connector to the level
net) ; therefore. Feather Falls line is
the actual observed elevations with no
adjustments.
144
Lines Bidwell and Bald Rock are connected
to the net at OM-20 and are observed
elevations without any adjustments. The
1977 elevation on the Bald Rock Terminal
Bench Mark (L1092) is 22 millimetres
(0.072 foot) lower than the established
1967 elevation. This elevation differ-
ence is within Class 2 first-order level-
ing limits and, therefore, may not be
indicative of a 22-millimetre (0.072-foot)
subsidence.
Line Richvale is also a spur line
connected to the level net at the west
side with excellent agreement between
October 1977 and October 1976. The
extreme west bench mark indicates 16
millimetres (0.052 foot) of subsidence
and the entire line varies between
(1976-77) 10 and 20 millimetres (0.033
and 0.066 foot) .
After Line 103 leaves the level net,
this spur line indicates the same type
Figure 72. Precise Level Net for Study of the Oroville Earthquake - 1977
145
divergence between 1976 and 1977; that
is about 20 millimetres (0.066 foot)
lower than 1976, using observed eleva-
tions. The 1976 data show uplift, and
the 1977 data indicate subsidence.
Potter shows approximately 10 millime-
tres (0.033 foot) of uplift in 1977 com-
pared to October 1976. The 1977 subsi-
dence is more than 20 millimetres (0.066
foot) compared to the reference date of
September 1967.
Elevation Differential Isograms
General . The elevation differential
isograms are hand-drawn representation
lines of equal vertical elevation differ-
ences for each epoch. By necessity, a
certain amount of judgement is used in
the determination of the contour lines .
Generally, the contours developed from
the spur lines are less credible because
they are observed elevations. Therefore,
these elevation-differential isograms
(Figures 73 through 78) are limited in
the area of the spur line, and care must
be used in interpretation of the contours
in these areas. The interpretation of
these spur line contours was intention-
ally limited by not developing contours
to their extremities; however, all data
for these spur lines are shown on the
vertical elevation differential plots.
September 1967 - October 1969 (Figure 73).
This epoch shows elevation differentials
during initial filling of Lake Oroville
starting in October 1967 and reaching
maximum lake elevation of 274.3 metres
(900 feet) in July 1969.
This isogram shows no subsidence south
of Lake Oroville and only minor subsidence
on the southeast side of the lake up to a
maximum of only 20 millimetres (0.066
foot) , based on spur line observed eleva-
tions. This isogram is limited in extent
because only 26 kilometres (16.2 miles)
of the original 1967 net were releveled.
It shows that only very minor subsidence
occurred during this period.
October 1969 - August 1975 (Figure 74) .
This epoch is the result of (a) the
normal lake cycling from 1969 to 1974,
(b) the lower-than-normal cycle in
winter of 1974 to elevation 228.6 metres
(750 feet) , (c) refilling to maximum
lake elevation in June 1975, and (d) the
effects of the August 1, 1975, Oroville
earthquake .
This isogram is also limited in extent
because of the short survey in 1969; how-
ever, it does show that only minor sub-
sidence was measured during August 1975
after the main shock, with most of the
subsidence occurring after this survey.
The maximum 1975 subsidence contour is
only 15 millimetres (0.049 foot) along
the southeast side of the lake.
September 1967 - October 1977 (Figure 75)
The 1967-1977, ten-year epoch, encom-
passes all measurable elevation differ-
entials from all causes. They include
the previous items plus the earthquake
aftershock sequence, and the effect of
the California drought, which resulted
in Lake Oroville being drawn down to its
lowest elevation of 198.1 metres (650
feet) in October 1977.
Generally, the subsidence adjacent to
Lake Oroville and Dam is fairly uniform,
ranging between 20-25 millimetres (0.066-
0.082 foot). A significant subsidence
area to the south and west of the dam
indicates increased subsidence away from
the lake and dam, especially in the
southern direction, to a maximum of 60
millimetres (0.20 foot).
Throughout the area south of Lake Oroville
the subsidence is quite predominant and
may be attributed to the fault zone.
August 1975 - October 1976 (Figure 76) .
This epoch includes only the immediate
aftershock sequence and decreasing lake
elevation from 274.3 metres (900 feet)
to 233.2 metres (765 feet).
146
+ UPLIFT
- SUBSIDENCE
OROVILLE EARTHQUAKE
EPICENTER Ml=5.7
AUGUST I, 1975
NOTES:
1. ALL CONTOURS ARE
IN MILLIMETRES
2. BENCHMARK OM-27 HELD
FOR FREE ADJUSTMENT
i
Figure 73. Elevation Differential I sogram— September 1967-October 1969
147
Figure 7^. Elevation Differential I sograni--October 1969-August 1975
148
LEGEND
+ UPLIFT
- SUBSIDENCE
OROVILLE EARTHQUAKE
EPICENTER Ml=5.7
AUGUST I, 1975
NOTES:
1. ALL CONTOURS ARE
IN MILLIMETRES
2. BENCHMARK OM-27 HELD
FOR FREE ADJUSTMENT
Figure 75. Elevation Differential I sogrann--September 1967-October 1977
149
+ UPLIFT
- SUBSIDENCE
OROVILLE EARTHQUAKE
EPICENTER Ml=5 7
AUGUST I, 1975
NOTES:
1. ALL CONTOURS ARE
IN MILLIMETRES
2. BENCHMARK OM-27 HELD
FOR FREE ADJUSTMENT
.1 .. . ,?
Figure 76. Elevation Differential I sogram--August 1975-October 1976
150
OROVILLE EARTHQUAKE
EPICENTER Ml=57
AUGUST I, 1975
NOTES:
1. ALL CONTOURS ARE
IN MILLIMETRES
2. BENCHMARK OM-27 HELD
FOR FREE ADJUSTMENT
Figure 77. Elevation Differential I sogram--October 1976-October 1977
151
LEGEND
+ UPLIFT
- SUBSIDENCE
OROVILLE EARTHQUAKE
EPICENTER Ml=5 7
AUGUST I, 1975
NOTES:
1. ALL CONTOURS ARE
IN MILLIMETRES
2. BENCHMARK OM-27 HELD
FOR FREE ADJUSTMENT
Figure 78. Elevation Differential I sogram--August 1975-October 1977
152
This epoch clearly shows subsidence to
the west of the nearly north-south zero
line. The magnitudes are small near the
dam and lake; however, significant
trends developed south of the lake. The
contours south of the Lake show a north-
south trending fault zone through lines
Mission Olive and Cleveland Hill. The
ground surface to the west shows a net
subsidence of 40 millimetres (0.131
foot) across this zone, with ground
rupture present in this fault zone.
October 1976 - October 1977 (Figure 77) .
This epoch includes continued lowering
of Lake Oroville — due to the drought —
of approximately 35.1 metres (115 feet)
and the declining aftershock sequence.
North-south uplift between the two north-
south zero lines is predominant for this
epoch. Significant uplift between the
two north-south 5-millimetre (0.016-foot)
contours is well defined with two areas
of 10-millimetre (0.033-foot) uplift.
The fault zone through lines Cleveland
Hill and Mission Olive is not clearly
defined during this time period. How-
ever, the area south of the dam defines
that previous area, although it shows
uplift of plus 5 millimetres (0.016
foot) compared to the previous subsi-
dence in this area.
August 1975 - October 1977 (Figure 78) .
This epoch includes the reduced lake
elevation of approximately 76.2 metres
(250 feet) and the entire aftershock
sequence shortly after the August 1,
1975, main shock.
This time period clearly shows the fault
zone through lines Cleveland Hill,
Mission Olive, and just south of the
lake. The north-south zero line separ-
ates the subsidence to the west and the
uplift to the east with the dam and lake
in the subsidence area. The magnitude
of movement adjacent to the dam and lake
is very small and insignificant. The
net subsidence across the fault zone is
approximately 50 millimetres (0.164 foot)
with lowering of ground surface to the
west.
Elevation Differential Along Lines
General. The plots of the elevation
differential for each of the lines are
based on a free adjustment holding OM-27
fixed. Spur lines are observed eleva-
tions based on the adjusted junction
bench mark elevation.
The Oroville area level lines are shown
on Figure 70 and the locations of the
bench marks are shown on Plate 2 (inside
rear cover) . The reference dates for
the individual lines vary according to
when the line was first established for
monitoring of the Oroville area. Also
shown on each figure is a plot of the
approximate ground profile along the
line for topographical referencing.
The lines listed below are presented in
alphabetical order along with comments
concerning significant movements and
anomalies.
Avocado (Figure 79) (Reference Date
February 1976)
1. Possible southern extension of
fault zone.
Bald Rock (Figure 80) (Reference Date
September 1967)
1. Spur line, observed elevations
only.
2. The October 1977 plot is approxi-
mately 20 millimetres (0.066 foot)
below the August 1975 plot although
within first-order survey error
limits.
Bidwell (Figure 81) (Reference Date
September 1967)
1, Spur line observed elevations
only.
153
Ul
UJ
o
z
< UJ
S a:
oc
6'^
1,
z a:
UJ
\
A
r-
O
/
/
/,
/
/
o
u
D
3
D
3
3 O
S3yi3wmiw Ni
lVliN3y3dJia NOIiVA313
S3yi3W NI
3nidoad aNnoyo xoyddw
15A
o
i33d _
d
01
o
-2180
■1980
■1780
•1380
-1180
o
00
'I
I
01
o
ac
1
?
\
\
2
o
IT>
O
s
10
2
O
iB
2
o
^
o-
o -
UJ
5
O
1
/
\
T
"
/
I
/
1
01 ' r>-
1
(
/
NOTES:
1. REFERENCE DATE
2. BENCHMARK OM-2
HELD FOR FREE
ADJUSTMENT
3 SPUR LINE
LEGEND
A 8-68
A 10-69
D 8-75
■ 2-76
3 r--
- r-
> O
:> •
<D
d
o-
UJ
2
OD
lO
S
o
^
d
\
\
\
lO
5
O
u>
2
o
O
o
ir
J
J
I
\
1
\
f
\
\
i
o
\
Q
_i
<
m
/
/
i
o
\
\
1
to
s
o
^
/
J <
\
i
o
\
\
\
/
z
o
^
^
\
\
^^^~-
\
A
.
ID
=
A
,1
OO
1
(Tl
s
o
\\
\
il
o
c
3 O "^ C
3" a "O O C
c
(
5
>
0 o o
01 Ol 01
m -t n
c
c
S3(JX3Nn~IIN N
1 nVIJ.N3M3Jdia N0UVA3n3
S3aj.3w Ni 3niJoad ONnoao xoaddv
155
/ft
yi:
K _. UJ
I in
UJ LJ O
LU
UJ
O
•?
o
m
O
<
m
^i
ID
3
o
o
CD
o
00 0>
m u>
IS u>
(^ 1^
S3Hi3WmiW Ml
nviiN3a3JdlQ N0I1VA313
S3yi3W Nl
snidOHd QNnods xoaddv
156
2. Close agreement of plots, except
that divergence starts at about
OM-42 to OM-48 where this line
connects to Bald Rock.
Bidwell Canyon Saddle Dam (Figure 82)
(Reference Date September 1967)
1. Spur line from OM-33.
2. Only minor subsidence is evident
up to about 20 millimetres (0.066
foot) .
3. Normal embankment consolidation is
shown at Moniaments 2 , 3 and 6
through 10.
Canyon Drive (Figure 83) (Reference Date
August 1975)
1. No significant subsidence after
the February 1976 survey.
2. Fifteen to 20 millimetres (0.049
to 0.066 foot) subsidence mea-
sured between August 1975 and
February 1976.
Cleveland Hill (Figure 84) (Reference
Date October 1975)
1. Spur line, observed elevations
only.
2 . Ground cracking occurred between
N and M.
3. Definite subsidence to the west of
the ground cracking.
4. Significant subsidence occurred at
the ground rupture between Novem-
ber 1975 and February 1976.
Dam (Figure 85) (Reference Date
September 1967)
1. Subsidence fairly consistent at
25 to 35 millimetres (0.082 -
0.115 foot) .
Duns tone (Figure 86) (Reference Date
February 1976)
1. Only minor variations of less
than 10 millimetres (0.033 foot).
Feather Falls (Figure 87) (Reference
Date September 1967)
1. Spur line fixed from Bench Mark
OM-27.
2. OM-27 is the fixed elevation bench
mark for the entire level net and
spur lines.
3. Consistency of the adjacent bench
marks (OM-26, H-925, H-80, and OM-
25) shows a stable area for the
fixed reference Bench Mark OM-27.
4. Localized discontinuity between
G1092 and OM25.
Foothill (Figure 88) (Reference Date
August 1975)
1. Consistent elevation after Febru-
ary 1976.
2. Fifteen to 40 millimetres (0.049 -
0.131 foot) of subsidence shown
between August 1975 and February
1976.
Miners Ranch (Figure 89) (Reference Date
September 1967)
1. Anomaly occurs at OM-17 (17 milli-
metres (0.056 foot) uplift October
1976 to October 1977) , possibly
disturbed by power pole installa-
tion.
2. Significant subsidence west of
Q-925.
Mission Olive (Figure 90) (Reference
Date October 1975)
1. Significant fault zone movement
between 4RBR and 5RBR. Ground
cracking observed between MO-4
and MO-5, MO- 7 and MO-8.
2 . Movement occurred between November
1975 and February 1976.
157
S3ai3wn"iiw Ni nviiNi3y3ddia noiivasis
158
<
o
o
O
<
o
z
10
0>
l£
o
UJ
z
<r
UJ
5
a:
I
u.
<J
<
II
2
or
o
o:
CD
li.
O ■ O •
m^
^
r
\
g
^
15
o
<
2 O
S3ai3wniiw
iviiNsaaddia
N0liVA3n3
S3ai3W Nl
siijoad QNnoao xoaddv
159
r
^
■*t-*fr
MOO
* O •
S3ai3wmiw Ni nviiN3a3Jdia NouwAsna S3ai3w ni anuoad ONnoaD xoaddv
160
©01 in UJ ^ N
O O 3
^ -1 ->
UJ Ul o
CD X <
f
-
\
\^
^
S3di3WnilW Nl nviiN3H3JJia N0liVA313
S3aj.3W Nl 31l30ad QNnOdO XOHddV
161
00 ffi to (D O) f--
kd id n n- n- r^
-1 1 —
I
J 1
\
A
o
Li>
>-^
S3ai3wmiw Ni
nVliN3a3JJI0 NOIiVA3n3
BTidoad QNnoao xoaddv
162
^ ^ hJ
a: w z
< m -
? ^-^
5 "■ Q:
2 0^?
uj o Q-
S3ai3wn"iiw iviiN3a3Jdia noiivasts
S3ai3lM Nl
3nidOad ONnoao xoaddv
163
^ ^
J
i
f
f
"f
f
1
\
J
io_l q_
CD o ® ^ o
S38i3WmiW Nl
nviiN3y3Jdia noiivashs
S3U13n Nl
3"1ldOMd QNnOMQ XOMddV
164
^ '2.
0 0 3
o uj d
^ (n cc
-St
Z Q. O
00 Oi lo ^ y? r-
O 4
d
UJ
o-
—1
o-
5
:
I
:
'^—
o_;
saaiawmm ni nviiN3d3ddia NoiiVAans
SByiaw NI 3nid08d oNnoyo xoaddv
165
o
o
1^
X
X
IC
o
o
m
rj 1-
1 <n
M-
t-
S^
1
o2
g s
10 <o u> I-.
I-- t~- N 1^
a:
1-
1- O
O Z
or iH
<UJ
2 a:
I U-
o
LEGE
X II-
(Nj ro c
■ :(f C
o
•
o-
=1 o-
s
iij
s
o
u o
-
(£
-
-■
rj
«>_
o
o
1333
o
o
1333
o
o
o
o
a.
o
o
m
(E
CO
1
(0
1
1
'^ UJ
r^
/
\
\C^
10
"^
/
i >
/
in
n"
-\
^ V
i\ O
/
g _i
r^
\
r^
VA
'
" o
\
o
o
(0
o
s
O
5
-
Z
\
^.
-==:a
\
^
•
T
^
2
1 J
O
o
OJ
O
5
to
■
L
\
■
I
_
5
\
—
;
Kv3
1
s
O O
o c
3 O
o c
3 O C
1
O
o
o
1
1
r ir> 0
1
O
o
o
S3ai3wmiw N
nwiiN3y3djia
N0liVA313
S3yi3W
Ni 3ii3oyd QNnoyo
XObddV
166
3. Magnitude of fault zone is approx-
imately 40 millimetres (0.131
foot) .
Morris (Figure 91) (Reference Date
August 1968)
1. Shows only minor uplift.
Olive (Figure 92) (Reference Date Sep-
tember 1967)
1. Significant subsidence trend at
OM-13 to a maximum of 63 milli-
metres (0.207 foot).
Oro-Bangor (Figure 93) (Reference Date
August 1975)
1. Almost stable line with the excep-
tion of minor uplift between
October 1976 and October 1977 be-
tween 20 BWSRM and SBM-2 up to
about 10 millimetres (0.033 foot) .
Oroville (Figure 94) (Reference Date
September 1967)
1. Anomalies at OM-6, W-145 and OM-50
indicate uplift from previous
trends, probably localized condi-
tions .
2. A major portion of the line has
subsided up to 40 millimetres
(0.131 foot) since September 1967.
Potter (Figure 95) (Reference Date
September 1967)
1. Spur line, observed elevations
only.
2. Almost perfect agreement between
October 1976 and October 1977.
3. Line subsidence of approximately
10 to 20 millimetres (0.033 to
0.066 foot) .
Thompson Flat (Figure 98) (Reference
Date September 1967)
1. Spur line, observed elevations
only.
2. Subsidence trend range from 10
to 20 millimetres (0.033 to 0.066
foot) .
Wyn-Miners Ranch (Figure 99) (Reference
Date August 1975)
1. Significant subsidence at the
southern end of this line between
A-234 and 5RBR ranging to 40
millimetres (0.131 foot) entering
into the fault zone .
103 (Figures 100, 101, 102) (Reference
Date 1957)
1. Spur line, observed elevations
only.
2. Minor variation of the October
1976 and 1977 surveys referenced
to the 1957 datum but all are
within the error limits.
1. Spur line, observed elevations
only.
2. Consistent pattern with some
variation.
3. The 1977 range of settlement is
approximately 20 millimetres
(0.066 foot) .
Richvale (Figures 96 and 97) (Reference
Date August 1975)
Oroville Dam Crest Differential Settle-
ment (Figure 103) (Reference Date
April 1969) (Referenced to Abutments)
General . Figure 103 is included only to
show the relationship of the earthquake
to the consolidation rate of the Oroville
Dam embankment. The graph shows that
the consolidation rate increased after
the July 1975 survey due to the August 1
earthquake; however, the same settlement
pattern continues. The lake elevations
13—78786
167
o
ID liJ 2
■-V I UJ
CD s
UJ w •"
< 2I
Q 0 5
-^ 0^ a> m vD to r^
" (D U) r^ r^ r^ f^
[2 '^ ^"^
J^ CD 0 <o ~ 0 0
^ 0 K lij
0 z 2 UJ
2 HI S IE
-■ a ^ D ■ 0 •
^ n: X u.
uj 0
li. Z (E
111 HJ 0
(E CD li-
0000
0000
0
0
a>
0^ f^ IT) fO
'-^S
'uj
u>
y
U1
N
f;-
0
\
" ^
01
2
\
©■
_/
CD
00
0
\
0
f^
\
,
/
to
\
H
2
/ .
u>
s
0
^-v^
9
N
I ,
0
a>
2
\
V "
\
\
0
\
\
*
\
i
00
S
-E
I
0
00
2
0
/
a:
0
_J
CE
\
/
\
_
/
cr°-
i ° •
2
0
>
2
0 .
;
1
I
/
\
S -
-
/
00
2
\
p
r
0
\
<D
0:
\
0 -
5
2
)
9
I
0
00
/
■'
0
\
0
\
OD
\
T^
S
r-
\
0
r-
\
i "
i
ID
00
9
— '
^
/
\
\|
u.
/
^
11
5
/
b 0
D 0 0 0 0 C
3 0
n in u
)
sr ro
S3ai3wniiw Ni
1VliN3M3Jdia NOIiVA313
S3H13M NI
3nidoyd QNnoao xodddv
168
ID
r-
ID
OD
o
00
CV)
o
O
■0
4
D
■
0
•
S3yi3wmiw Ni nviiN3a3ddia noiiva313
S3M13W NI 3"lldOad QNnoyO XOMddV
169
QTj CD O 00
o
<
CD
I
o
cc
o
S3ai3wmiw Ni
lVliN3d3Jdia NOIiVASHS
S3ai3W NI
3nijoad QNnoao xoaddw
170
S 2 o
o
I33d °
_
S g ° I33d
V
T r
s
r
o
/
/
o
s
Q
■\
\
, \
o
\
\
in
\
V,
'T
\
\
L
i
/
o
/
o
2
00 01 in (D
ID r^
/
/
(H ID f^ N.
f^ r^
/
/
O
eo o 00 00
o o
/
j
o
s
-'
O 4 □ ■
o •
/
//
o
L
^
9
'
^
ID
o^
\ >
-
L
\
CD
1
s
UJ
Y
^
o
\
_l
\
-J
o
in
>
O
cr
O-
s
o-
>-
/
o
r-»
/
/
1*^
/
lO
o
CM
/
O
~
1/
t--
s
/
/
/
y
A
o
1
/
CI
to I C
^
I
to
/
^ RiK
^^
1
o
/
K i "
^~^-~^
^^
=
/
U5 § oq
1
o
I
iii^
2
\
£ S*^
r
m o
^
u. z a:
o
a: CD li.
10 7
- rj
- /
1
s
\
.VL
_ o
/
o o o c
3 O O C
> c
> c
>o o
2 <=
c\j ro * m u
5 O
S3ai3wmiw Ni
lVllN3a3d3ia N0liVA3n3
S3ai3N
NI 3nidoad ONnoao xoaddv
171
CO^ O 1
lO
o
-
(Jl I--
< ^s
UJ
2 £ 5o^ q: ^
tD (^ h- r^ N r^
(DO oo ro o O
<] 4 a ■ o •
o-
LU
d o-
s
5
o
uj ijj UJ Q Q.
c mi <t en
-
- CM CO
CO
o
o -
1333
i33d
CM
CM
° o S
° o 9
O o
S
o
r
r
y^
J
o
f^
/
f^ /
00
^
o /
• /
o
1^
s
o
r^
T
T
r-
/ ;
/
O
//
/
(Jl
s
\
o
1
//
^
c^
CO
^^----__
\
\
o
--"^^
\
\
v
^-.►i
1
s
o
\
CC
t
/
1
\
/
UJ
ID
i
s
5
1
1-
1-
o
Q.
^
Vv
\
o
\\
\
\
T
n*-
>,
1
CO
2
Ti
^
o
\
1
CO
\
1
2
o
/
'
'
(
CO
2
1
/
o
\
/
3
J
A ii h
i
s
o
O
t^
r 1 1 /
w
V
b iiU:
S
CO
2
O
^-----
o o
"s
\ I
7
\
01 +
c
r^^ jJ*L ^w
\
3
D
D O
3
D C
3
D C
in u
^
7 7 7
•«■ in ci) h- c
N
^
S3ai3wmiw Ni 1
?liN3H3JJia NOIiVA313
S3ai3W
NI siuoacj ONnoao xoadcjv
172
<
Q
O
10
01
CO
r^
h-
IC
4 J
t Ul
III
o
o
C\J
o
O
7-
UJ
OC
<
4
D
■
o
•
i
liJ o
CL
6
o-
5
o -
-
-
.
_
-
:
lO _
O J
— m-
r
1
}
,.
o
c
J
1 — "^^
" — r
1
\
nVliN3d3ddlQ N0iiVA3T3
S3813W NI
3niJ0dd ONnOHD XOHddV
173
X
^
< <
"1
/ o
1
'
J
1
/
o
1
/
\
1
/
; At
/
d
o -
'^
O-
-
5
_
J
-
lO J
O J
UJ
_J
< CM
> li.
X °
C_) CM
5
UJ 5 o: ^
a: X u. -■
'i^ z a: %
S3ai3wnniw ni
lVUN3y3ddia N0I1VA313
S3iJ13N NI
3nidoad QNnoyo xoaddv
174
tD O
o> lo <*> u) r-
1
/
/
' — H
\
\
\
nviiN3a3djia N0ii\rA3n3
S3dl3M NI
3niJ0dd ONnodo xoaddv
175
m (i) ID N
saaiawiniw
/
I
z
<
v>
cr
1VliN3H3dJia NOIiVABTB
S3ai3W Nl 31U0Md QNOOyO XOdddV
176
CO o> m ^ (D
S3ai3wmm u\ ivixN3M3ddia NOiivAana
S38i3W Nl 3Tld08d ONnOWS XOMddV
177
in 1"
<n I < Si
(S ot m u> ifi r-
II I I I I
00 O 00 Ol o O
< 4 o ■ o •
4-
-A
r —
1
\
/
\
/
-V
/
Jk 1
fO
o
l\
saaiawmiw ni nviiN3H3djia NOiiVA3"i3
S3yj.3w NI snijoyd ONnowa xodddv
178
oc UJ lAj z
< q: 5 z uj
5O J - o
00 3 q: -'
tc ID f^ r^ r- p^
<] 4 O
\
\
K
r--
0
1
I
\
\
0
-^
S3yi3wmiW Nl lVllN3a3JJia N0liVA313
S3Mi3lA; Nl 311d08d QNnoyO XOHddV
179
^^
o
o
^
^
\
o
S"
z
2
1-
1-
SUTMENT
PI AND 926
\
K
o
o
o
- S
-^ c
o
■
DATE 4-65
FERENTAL S
BETWEEN AE
JCHMARKS S
d
\1
i33d ^
6 6 6
^^
^
Jt' tr Q
0
^ m
1
^
1
i
V
5S
/
0 -
1 _-
/
<
1-
<
3
•a
r^
/
- N
IT
\\
\ \
\\V
\
S
"
/
r- \
5
UI
q:
/
/ ~J 7
k2
/jy
\
/
//
//^
;
-g /
//
/ / /
///
Y
/
/
(
s
<-
Q.
MW) i
(C
>J3IM3nii3S
to / /
////
y/^
Y
/
v)/
M
r
P P
~ P P 1-
i. U. li. u.
0 OJ 01 IC
o
//^
V//^
>
<
848
754
889
871.
828
752
742
705
648
889
z
o
///o^
S2525S5SSS2
"i
H
27-72 25'
3-73 25£
0-74 22<
B-75 27C
2-75 26:
7-76 252
2-76 22s
0-77 — 22€
4-77 214
5-77 197
B-78 271
U-
0
1
!y f^ 00 «> =
1
- <i 9 <o
UJ
UJ
LU
CO
— in
■t-J 4J
c c
1
(U (U
<
I- E
0) +J
h-
<4- ZJ
^
— <
LlJ
Q
cr
0)
•4-> £
Ul
in *J
ii
(U
u.
1- 0
0 JJ
n
1-
03 4)
Q 0
U)
C
III
<U (U
ir
— 1-
— 0)
0
.- <4-
> (U
S
0 Qi
<i
0
Q
UJ
(ujuj) iN3W31ii3S
180
at the time of the surveys are tabulated
on the plot.
Commentary
The Department is requesting the National
Oceanic and Atmospheric Administration
(NOAAO to relevel key bench marks, espe-
cially OM27, when they rerun their first
order network in the Oroville area.
The annual releveling frequency of the
Oroville area network will be decreased
to a longer interval not to exceed five
years .
Conclusions
The following conclusions are based on
free adjustment holding the elevation of
OM-27 fixed (1967 USC&GS adjustment) and
therefore, all elevation differentials
are relative to OM-27.
1. Based on the preearthquake datum of
1967, the greatest elevation differ-
ential was only 63 millimetres
0.207 foot) on line Olive during the
ten-year epoch (1967-1977) ,
2. The August 1, 1975, Oroville earth-
quake is associated with minor sub-
sidence in the Oroville area, mainly
south and southwest of Lake Oroville.
3. Most of the subsidence associated
with the August 1, 1975, Oroville
earthquake was measured between late
August 1975 to October 1976.
4. The elevation differentials show
movement of the fault zone that
passes through the level lines
Cleveland Hill and Mission Olive
(ground cracking was evident before
the lines were established) . A
fault zone may pass through the level
lines Miners Ranch south of Lake
Oroville; however, no ground crack-
ing was found there .
5. Minor subsidence of less than 25
millimetres (0.082 foot) has been
measured adjacent to Oroville Dam
and Lake between 1967 to 1977 due
to all causes.
Horizontal Earth Movements
Introduction
During 1967, the Lake Oroville horizontal
monitor network was established to iden-
tify movement that might be associated
with filling of Lake Oroville and changes
that could occur in the event of major
tectonic activity. Figure 104 shows
the Horizontal Geodetic Control and
Triangulation Net, 1967-1975, as refined
to this latter date.
Horizontal Geodetic Control and Triangu-
lation Programs
September 1967. The 1967 original hori-
zontal monitoring. Class 1 first-order
triangulation, included four base lines
measured by a geodimeter. A total of
14 stations were established. Ten con-
crete piers, with stainless-steel instru-
ment adapters cast into them, were con-
structed. A permanent tower 6.1 meter
(20 feet) high, constructed with 103-
millimetre (4-inch) galvanized pipe with
a stainless-steel instrument adapter,
was built on Kelly Ridge because of
restrictions regarding the cutting of
trees and brush set forth by the Division
of Beaches and Parks. The remaining
stations were those of the U. S. Coast
and Geodetic Survey. Metal instrument
stands were erected over them and bolted
to rocks to avoid disturbing the station
marks. Triangulation station Bald Rock
is located in the same diorite rock mass
as the northernmost bench mark.
Observations were made at night and con-
sisted of 16 sets of directions taken
with a first-order theodolite.
The observation at Gaub did not have
pointings to Oroville that would have
extablished an azimuth at the westerly
extreme of the net and did not have any
observations to or from Bald Rock to fix
181
C^L
OROVILLE EARTHQUAKE
EPICENTER Ml- 5 7
AUGUST I, 1975
I .5 0 I
I .5 0 I
L_LJ I
KILOMETRE
Figure 104. Horizontal Geodetic Control and Tri angul at ion Net (1967~1975)
182
any orientation at the northeasterly
extreme, nor was an astronomical azimuth
observed from any station.
Seven lines were measured with a Model
2A Geodimeter providing the scale for
the net. Three lines were measured on
two successive nights; the remaining
four were single observations. The 2A
Geodimeter was considered a first-order
base-line instrument.
April 1968. The second observation pro-
gram of the horizontal net at Lake Oro-
ville was conducted during the period
from April 1 through April 12, 1968. A
small change was made in the original
triangulation net. Observations from
the original station Spillway became
blocked by a fence; therefore, it was
reestablished in the other spillway
abutment. A property owner requested
the removal of station Potter. Hence,
Potter 2 was established on State prop-
erty. Observations were made to and
from the original station Potter before
it was removed.
Observations were made at night and con-
sisted of 16 sets of directions (32
pointings) with a first-order theodolite.
Three of the lines measured in 1976 were
remeasured.
Comparison at that time between the ini-
tial observation in 1967 and that in
April 1968 resulted in no detectable
horizontal movement.
August - September 1975. During August
and September 1975, after the August 1,
1975, Oroville earthquake, the Lake
Oroville horizontal monitor net was
reobserved. Night-time observations
from the 16 existing stations were made
with a Wild T-3 Theodolite, using the
16-set criteria at each station.
Several stations have been replaced
since the original 1967 work:
Potter 1 replaced by Potter 2 in 1968
Spillway replaced by Spillway 3 in 1968
Kelly 2 replaced by Kelly 2 Eccentric
in 1972
Computations and Analyses
In general, the comparison of observed
angles for 1967, 1968, and 1975 shows
little change. The observations at
Spillway 3 (1968 vs. 1975) indicate a
five-second difference; however, an exam-
ination of the triangle closures revealed
that the 1968 index pointing from Spill-
way 3 to ODPT was in error , and this
line was deleted from the recomputation
of the 1968 work.
The lack of any direct azimuth orienta-
tion for the 1967 observation was cor-
rected in 1968. The original computa-
tions show the Department's 1968 position
for Bald Rock instead of the U. S. Coast
and Geodetic Survey (USC&GS) published
value. This 1968 value determination
had been used in both the original 1967
and 1968 computations. Difficulties were
encountered when the 1968 repositioning
of USC&GS second-order station Bald Rock
was checked. Apparently, computations
had progressed from Bald Rock through a
fully-observed traverse to USC&GS first-
order station Gaub. This closure error
was somehow transferred back to Bald
Rock and a new position established.
Using the original 1967/68 field data,
this traverse was recomputed with a
closure error on the Bald Rock USC&GS
published position of 24 millimetres
(-0.08 foot) north, and 9 millimetres
(-0.03) foot) east. The standard devia-
tion of the direction work was 0.44
second and the length error ratio was
one part in 377,640. This closure
error was much less than the 88 milli-
metres (-0.29 foot) north and 49 milli-
metres (+0.16 foot) east, indicated in
the original 1968 computations. Since
it appeared that the USC&GS published
position of Bald Rock was actually com-
patible with the other first- and second-
order stations in the area, all work was
recomputed on this basis.
Length measurements were used in the
computations to check the position of
H— 78786
183
Bald Rock, but only one length (Line 2
to Bald Rock) has been used for the 1967/
196B and 1975 complete net computations .
All computation and recomputation was by
the Department of Transportation "Cosmos"
Computer Program, which is a least
squares adjustment by variation of geo-
graphic coordinates. Probabilities as
computed in the program were :
1967 Monitor Net - 0.45 seconds standard
deviation for directions - lengths
1 part in 467,049.
1968 "Bald Rock" Traverse - 0.53 seconds
standard deviation for directions -
lengths 1 part in 391,512
1968 Monitor Net - 0.74 seconds standard
deviation for directions - lengths
1 part in 282,029
1975 Monitor Net - 0.78 seconds standard
deviation for directions - lengths
1 part in 267,022
Although the errors and adjustments
appear quite small, the computed dis-
tances have not matched measured lengths
as well as could be expected. The com-
puted lengths are plus or minus 50
millimetres (0.164 foot) long, as com-
pared to measured lengths. During the
1975 observations, the U. S. Geological
Survey measured two lines in the Oroville
Monitor Net, incidental to other work
they were involved with. The measured
length, Kelly 2 Eccentric to Cameron, is
103 millimetres (0.338 foot) shorter
than the computed length. The measured
length, Kelly 2 Eccentric to Line 2, is
46 millimetres (0.151 foot) shorter than
the computed length. Five short lines
were measured with the MA/100 telluro-
meter by the Department during February
1976; the Line Kelly 2 Eccentric to
Line 2 was within 5 millimetres (0.016
foot) of the uses measured distance.
The other four lines were about 50 milli-
metres (0.164 foot) shorter than the
computed distances. The Line Kelly 2
Eccentric to Cameron is beyond the MA/100
range .
Comparative coordinate position changes,
in millimetres, from the 1967 observation
are:
1968
1975
mm
feet
mm
feet
Loafer
North
-37
-0.12
-37
-0.12
East
-12
-0.04
+85
+0.28
Island
North
-37
-0.12
+18
+0.06
East
+ 21
+0.07
+ 85
+0.28
Reed 2
North
- 9
-0.03
-43
-0.14
East
+15
+0.05
+ 9
+0.03
Spill 3
North
_
_
- 6
-0.02
East
-
-
- 3
-0.01
OPDT
North
-12
-0.04
-49
-0.16
East
- 9
+0.03
+ 9
+ 0.03
Morris
North
- 6
-0.18
-15
-0.05
East
+ 3
+0.01
+ 3
+0.01
Cameron
North
-55
-0.18
+ 30
+0.10
East
+ 9
+ 0.03
+94
+0.31
184
1968
1975
mm
feet
mm
feet
Intake
North
-27
-0.09
-34
-0.11
East
- 3
-0.01
+27
+0.09
Line 2
North
-21
-0.07
-12
-0.04
East
+18
+0.06
+ 9
+0.03
Potter 2
North
-
-
+ 6
+0.02
East
-
-
0
0
The computed movements of the stations
of this net are insignificant; and, in
many cases, within the accuracy of the
surveys. It appears that there is a
scale problem in the network, but the
effect on comparative position differ-
ences would be slight. Results of the
1975 survey indicate a north and east
expansion of the easterly portion of the
net. However, the measured lengths from
Kelly 2 Eccentric to Loafer and Cameron
as compared to computed lengths , do not
support this indicated change .
Commentary
The 1975 observations and calculations
were to be a duplicate of the 1967 and
1968 work. However, all stations visible
from each occupied station were observed,
and all directions used in the computa-
tions. Therefore, some of these observed
lines form extremely poor figures and
adversely affect the final station
positions.
Based on the comparison of preearthquake
(1967) and postearthquake (1975) values,
using all observations, the greatest
computed movement occurred at station
Cameron, with a movement of +98 milli-
metres (+0.32 foot) northeasterly.
The Oroville Horizontal Geodetic Control
and Triangulation Net is being refined
to include only strong figures. All the
previous surveys will be recalculated
on this basis for comparison to future
surveys.
Conclusions
1. All computed horizontal movements
are minor and in many cases within
the accuracy of the existing surveys
and computations .
2. The August 1, 1975, Oroville earth-
quake did not cause sufficiently
large horizontal movements that
could be reliably measured and
calculated within the Lake Oroville
Monitoring Network.
185
CHAPTER V
OROVILLE DAM:
EVALUATION OF SEISMIC STABILITY
Acknowledgements for Chapter V
For some time before the earthquakes of 1975, the Division of Safety of Dams
had been working on static and dynamic analyses of Oroville Dam as part of their
program for developing dynamic analysis capability. After the earthquakes, the
Divisions of Operations and Maintenance and Design and Construction undertook the
analysis of seismic preparedness and safety of the Oroville Complex including an
evaluation of seismic stability of Oroville Dam. Much of the work already completed
by Division of Safety of Dams was used in this evaluation, and they were requested
to participate in the additional studies following the earthquake.
John Vrymoed performed the static and most of the dynamic finite element
analyses, and interpreted the acceleration records of the 1975 earthquakes. He
Sso prokded advice on additional dynamic analyses. His office report. 'Dynamic
Analysis of Oroville Dam." provided most of the material for several chapters and
much of the additional information for this report.
Bill Bennett planned the cyclic test program for Oroville gravel and carried
out the first 20 tests. His report. "Evaluation of Sample Density for Triaxial
Testing of Oroville Gravel," is the basis of the discussion of sample density in
Section 8.
Emil Calzascia made the modifications to the Pacoima and Taft acceleration
records to develop the acceleration time history for the ^^f ^ly^^^^^^'^^jjj^^^^^f J„
did the filtering and corrections to acceleration records of the 1975 earthquakes to
produce acceleration time histories and response spectra.
Through many discussions. Rashid Ahmad, Emil Calzascia. Bill Bennett, and
John Vrymoed of the Division of Safety of Dams contributed immeasurably to the under-
standing of complex aspects of the analysis, and suggested methods for solving prob-
lems associated with three-dimensional effects.
Harry Kashiwada of the Soils Laboratory made many trips to Richmond to assist
in conducting the cyclic triaxial tests, first with Bill Bennett and later with
N. Banerjee.
N. Banerjee took over the cyclic testing and completed the program, under the
direction of Professor H. B. Seed.
I The guidance and advice provided by Professor Seed during the studies is
I especially appreciated.
187
INTRODUCTION
Background
Oroville Dam is situated on the Feather
River in the foothills of the Sierra
Nevada above the Sacramento Valley. The
dam is 8 kilometres (5 miles) east of the
City of Oroville and about 113 kilometres
(70 miles) north of Sacramento (see
Figure 105) .
Oregon
SAN FRANCISCO
MILES
Figure 105.
It has a maximum embankmen
235 metres (770 feet) and
of 1 707 metres (5,600 fee
gated spillway to the left
The 61 000 000 cubic metre
cubic yards) embankment is
inclined impervious gravel
founded on a concrete core
sand-gravel-cobble transit
shells upstream and downst
t height of
crest length
t) from the
abutment.
(80,000,000
made up of an
-clay core
block, with
ions and
ream.
KILOMETRES
Location Map
Historically, there have been some mod-
erately strong earthquakes in the Oro-
ville region. However, when the dam was
built in the early 1960 's, there were no
known active faults within 32 kilometres
(20 miles) of the dam. Design to resist
earthquakes was a major consideration,
and the best methods available at the
time were used. Embankment slopes were
analyzed by modified Swedish slip-circle,
sliding-wedge, and infinite-slope meth-
ods, with a 0. Ig horizontal acceleration
force included to represent earthquake
loading. The upstream slope of the em-
bankment was investigated to find the
critical conditions for stability with
several reservoir levels. The minimum
safety factor found was 1.2 for the up-
stream slope, with the reservoir lowered
90 metres (300 feet).
In addition, a series of shake table
tests, using a 1:400 scale embankment
model, were conducted by Professor Seed
at the University of California at
Berkeley; he also performed analytical
studies to calculate seismic coefficients
for the dam for the El Centre earthquake
(maximum acceleration = 0.25g), to esti-
mate soil strengths that would exist in
the gravel shell during an earthquake,
and to determine safety factors for up-
stream sliding wedges. Seismic coeffi-
cients varied from O.lg to 0.25g,
strengths (friction angle of gravel
shell) varied from 42° to 38°, the in-
clination of contact force between wedges
varied from 0 to 20°, and resulting safe-
ty factors varied from 1.75 to 1.
On August 1, 1975, an earthquake of Rich-
ter Magnitude 5.7 occurred about 12 kilo-
metres (7.5 miles) from the dam. The
Oroville earthquake series began with a
number of foreshocks on June 28, 1975.
Then on August 1, twenty-nine foreshocks
occurred within 5 hours of the main
shock. The largest of these foreshocks
had a magnitude of 4.7. Many after-
shocks, with magnitudes up to 5.1, oc-
curred throughout August, and scattered
shocks continued for many months.
I
The embankment performed well in all the
shocks of the Oroville earthquake seq-
uence, which produced accelerations at
the base of the dam of about O.lg on
three different occasions. Instrument-
ation results indicated maximum permanent
displacements of about 25 millimetres
(1 inch) , pore-pressure rise in the core
of 15 metres (50 feet) , and maximum tran-
sitory pore-pressure response in the up-
stream transition of 83 kilopascals (0.8
TSF) . Performance of all Oroville area
water-project structures is detailed in
DWR Bulletin No. 203, "Performance of the
Oroville Dam and Related Facilities Dur-
ing the August 1, 1975 Earthquake".
Even though the embankment performed well
in the 1975 Oroville earthquake, it be-
came apparent that active faults were
quite close to the dam. The question be-
came: What earthquake is now appropriate
for analysis of Oroville Dam, and how
will the dam perform in that earthquake?
To answer this question, the Department
of Water Resources began the comprehen-
sive investigation described in this
report.
The dam performance was to be evaluated
by the latest state-of-the-art procedures,
which included cyclic-strength testing of
gravels, studies of the observed embank-
ment response to ascertain the in-place
shear modulus of the gravel shells, and
static and dynamic finite-element-method
analyses to determine stresses in the em-
bankment. To assist in the evaluations,
the Department convened a special consult-
ing board of foremost specialists in geo-
logy, seismology, dynamic analysis, and
practical dam design. This board has
provided guidance in completing the stud-
ies discussed in this report and has re-
viewed the findings.
Commentary
1. It is generally accepted that very
dense cohesionless soils will not de-
velop liquefaction flow slides. The
cyclic triaxial tests on Zone 3 grav-
els provide additional support for
this concept. Pore water pressures
might rise momentarily to the value
of the confining pressure on any load-
ing cycle, but would then drop quickly
as the sample strained. In order for
a flow slide to be possible, pore
pressure would have to remain high as
strain progressed.
In evaluating embankment performance,
liquefaction flow slides were not con-
sidered possible. The objective was
189
to make the best estimate possible of
the extent of deformtions that would
be caused by earthquake shaking.
2. An apparent discrepancy has been noted
by the profession between strains in
laboratory test samples and strains
calculated by dynamic analyses. For
dynamic stresses developed in an em-
bankment during strong earthquake
shaking, calculated linear elastic
shear strains may approach 1 percent.
At the same stresses, laboratory sam-
ples could reach 5- to 10-percent
shear strain. Developers of dynamic
analysis procedures generally contend
that calculated stresses are correct
even though the strains may be
incorrect.
In situations where initial static
shear stresses are high, the strain
in any one cycle may be about the same
in a test sample as that calculated
for a field element. Sample strain
accumulates incrementally in one di-
rection until the accumulated strain
is 5 to 10 percent. On any one cycle,
shear strain may not be much greater
than 1 percent.
However in other situations, where
initial static shear stress is small-
er, the strain on any one cycle gen-
erally reaches several percent.
3. There has not been any method devel-
oped and verified for calculating em-
bankment deformations caused by earth-
quake shaking, other than the rough
estimate of average shear strain po-
tential times height, made for Upper
San Fernando Dam. This dam developed
very high strain potentials, and prob-
ably a liquefied interior zone. It is
not at all clear that the same method
would apply to a case with much small-
er strain potentials and no liquefied
zone. For example, it is commonly
accepted that a dam which develops
compressive strain potentials of less
than 5 percent will not suffer signi-
ficant deformations. But, if the des-
cribed method is used, displacements
of many feet would be calculated for
a high dam with average compressive
strain potential of only 2 or 3
percent.
4. The investigation was limited to the
upstream shell whose strength might be
reduced during earthquake shaking be-
cause of saturation and possible lack
of drainage. The downstream shell is
essentially dry and would presumably
retain full drained strength and
therefore would develop smaller
strains. The core is a compacted clay
-gravel, a type of material found to
perform well in strong earthquake shak
ing. On the basis of these consider-
ations, the maximum deformations would
be expected in the upstream shell.
Summary of Findings
1. Oroville Dam is in a narrow canyon
relative to the height of the dam,
which complicates the problem of anal-
yzing earthquake response. Abutment
restraint has a significant effect on
natural period, accelerations, dis-
placements, and stresses. Two-
dimensional methods of dynamic anal-
ysis will not give correct values for
these response factors. However, a
two-dimensional analysis can be forced
to give the correct period and crest
accelerations (when they are known
from crest acceleration records) by
deliberately using an incorrect
(pseudo) modulus for the embankment
soil. An extension of this approach
was used to take into account the
abutment restraint effects on shear
stresses generated by the Reanalysis
Earthquake. A basic assumption was
that the same pseudo shear modulus
which gave the correct response in the
recorded earthquake will also give the
correct response in a stronger earth-
quake. The effect of abutment re-
straint is to reduce shear stresses
significantly in the upper part of
the embankment .
190
2. The cyclic strength of dense cohesion-
less soil is difficult to assess, par-
ticularly at consolidation stresses
lower than the critical confining
pressure. Cyclic triaxial tests were
carried out on dense samples of
Monterey "0" sand and Oroville sand at
low isotropic consolidation stresses,
with special attention given to ob-
serving sample behavior. The results
indicate that dense samples strain as
uniformly as do loose samples, and
that higher strains are produced when
higher cyclic stresses are applied.
These observations hold true even for
cyclic stresses higher than the con-
solidation stress. However, it was
found that strain occurs only in the
extension direction for dense sands.
Studies by others on dense Monterey
"0" sand also showed that triaxial
sample strain is all in the extension
direction, but that triaxial stress-
strain behavior still correlates with
shaking-table stress-strain behavior.
These tests all used cyclic triaxial
stresses less than the consolidation
stress.
On the basis of all these studies, the
cyclic triaxial test is considered to
be as applicable for evaluating cyclic
strain behavior at consolidation
stresses lower than critical confining
pressure as at consolidation stresses
above critical confining pressure.
However, further studies are needed
at higher cyclic stresses to extend
the correlation between cyclic triax-
ial and shaking-table tests.
The cyclic triaxial tests on Oroville
gravel were used to determine cyclic
shear strength envelopes. For some
tests, curves of strain vs. number of
cycles were conservatively extrapolat-
ed, because cyclic load dropped or
apparent sample necking occurred early
in the test.
3. Many of the analysis conditions and
soil properties could not be deter-
mined precisely. Ranges of support-
able choices and values were defined
by testing, analysis of observed per-
formance, and comparison with other
published data. Embankment displace-
ments were estimated for two cases de-
fined as follows :
a) Best Judgment Case — For each ana-
lysis condition and soil property,
use the value within the defined
range that is best supported by
available evidence and judgment.
b) Conservative Case — For each ana-
lysis condition and soil property,
use the end of the defined range
that produces the higher estimated
displacement.
Predicted behavior of the dam, based on
the "best judgment case," is that no
slides or large movements will develop;
but permanent displacements on the order
of a metre could develop at the surface
of the upstream slope. This predicted
behavior is considered conservative in
many respects, and the possibility of
greater displacements is considered
remote.
Displacements were also estimated for
the "conservative case," which is consi-
dered the extreme behavior that could be
postulated from the defined ranges of
soil properties and conditions. The sur-
face of the upstream slope might undergo
displacements of 10 metres (33 feet) be-
tween the two berms, slumping near the
upper berm, and bulging near the lower
berm. Although uncomfortably large,
these movements would not threaten the
safety of the dam. Remember, this is
not the predicted behavior, but the ex-
treme limit that could be postulated if
all soil properties and conditions were
more adverse than the best judgment
choices.
Conclusions
1. The seismic stability of Oroville Dam
was investigated for the Reanalysis
Earthquake of Richter Magnitude 6.5,
at a hypocentral distance of 5 kilo-
metres (3 miles) from the dam, and
producing the following ground motion
191
characteristics at the base of the
dam:
maximum acceleration
predominant period
duration
acceleration time
history
0.6 g
0.4 seconds
20 seconds
modified Pacoima
plus modified
Taft
It was concluded that this ground shal
ing was more severe than any future
shaking likely to affect the dam.
2, Using "best judgment" choices for in-
put soil properties and conditions,
relatively small embankment deforma-
tions were estimated by the seismic
evaluation procedures. It is con-
cluded that Oroville Dam would perfon
satisfactorily if subjected to the
Reanalysis Earthquake.
2. DESCRIPTION OF EMBANKMENT MATERIALS
AND DYNAMIC INSTRUMENTATION
Embankment Materials
Materials comprising the various zones
of the dam considered in the analyses
are shown on Figure 106. Gradation
curves for these materials are shown on
Figure 107.
CO
^ 300
I-
liJ
O 100
I-
<
>
LU r,
N.W. S. ELEV. 274.3m(900ft)
CREST ELEV. 281.0m (922ft)
ZONE I a 4 - 6 900 000 CUBIC METRES (9,000,000 CUBIC YARDS)
IMPERVIOUS
ZONE 2- 7 260 000 CUBIC METRES (9,500,000 CUBIC YARDS)
TRANSITION
ZONE 3- 46 710 000 CUBIC METRES (61, 100,000 CUBIC YARDS)
PERVIOUS
RIPRAP- 315 700 CUBIC M E TRES (413,000 CUBIC YARDS)
CONCRETE - 222 500 CUBIC METRES (291,000 CUBIC YARDS)
Figure 106. Oroville Dam Maximum Section
192
200
100
80
100
50
30
U.S. STANDARD SIEVE SIZES
16 8 4 3/8" 3/4" I-I/2'
'
1
1
1
y
'
/
/
/
/
/
/
/
/
:/
^
/
/
/ y
/
/
0
,el^
^
A
/
zoD
r^
/
A
^
JO
fioni^
^
y
J
ri
\^£^
'Shelll
/
-f
1
1
1
1
0.1
0.5 1.0 5.0 10.0
GRAIN SIZE IN MILLIMETERS
50.0 100.0
Figure 107. Average Gradation Curves of Oroville Dam Materials
The materials used in each zone and the
compaction methods were:
Zone 1 — Impervious core consisting of a
well-graded mixture of clays, silts,
sands, gravels, and cobbles to 8 centi-
metre (3- inch) maximum size. Compaction
was in 25-centimetre (10-inch) lifts by
90.7-tonne (100-ton) pneumatic rollers.
Average in-place dry density achieved
was 2 2A3 kilograms per cubic metre (140
pounds per cubic foot) at 8.0 percent
moisture (average 100 percent compac-
tion, DWR standard 20,000 ft-lbs per
cubic foot).
Zone 2 — Transition consisting of a well-
graded mixture of silts, sands, gravels,
cobbles, and boulders to 38-centimetre
(15-inch) maximum size (6-percent limit
on minus No. 200 U. S. Standard sieve).
Compaction was in 38-centimetre (15-
inch) lifts by smooth-drum vibratory
rollers. Average in-place dry density
achieved was 2 419 kilograms per cubic
metre (151 pounds per cubic foot) at
3.9 percent moisture (average 99 per-
cent compaction, DWR standard vibratory
maximum density test).
Zone 3 — Shell of predominantly sands.
193
gravels, cobbles, and boulders to 61-
centimetre (24-inch) maximum size (up to
25 percent minus No. 4 U. S. standard
sieve sizes permitted) . Compaction was
in 61-centimetre (24-inch) lifts by
smooth-drum vibratory rollers. Average
in-place dry density achieved was 2 355
kilograms per cubic metre (147 poimds
per cubic foot) at 3.1-percent moisture
(average 99 percent compaction, DWR
standard vibratory maximum density test).
Zone 4 — Buffer zone designed to compress,
contains between 15 and 45 percent pass-
ing No. 200 U. S. standard sieve with 20-
centimetre (8- inch) maximum size. Com-
paction was in 38-centimetre (15-inch)
lifts by a smooth-drum vibratory roller.
Average density was 1 666 kilograms per
cubic metre (104 pounds per cubic foot).
(Average 82-percent compaction, DWR
standard 20,000 ft-lb per cubic foot.)
Dynamic Instrumentation |
The embedded dynamic instrumentation sys-
tem at Oroville Dam has been operating
on a limited basis since the August 1975
earthquake. Since then the system has
deteriorated to a point requiring a com-
pletely new present "state-of-the-art
system" in order to obtain reliable, con-
sistent dynamic records. Following is a
description of the original system and
the upgraded system.
Original System
The originally installed djmamic instru-
mentation system at Oroville is inoper-
able. This system included four force-
balance type accelerometers, 6 pore pres-
sure sensors, and 15 soil-stress cells,
installed at the maximum section (Statioi
53 + 05) as shown: on Figure 108.
• PORE PRESSURE CELLS
■ ACCELEROMETERS
"^ SOIL STRESS CELLS
N.W.S. ELEV. 274.3m
(900 ft.)
CREST ELEV. 281.0m (922ft.)
ELEV. 45.7m ( 150 ft.)
FEET
Figure I08. Oroville Dam Embankment, Original Dynamic Instrumentation
194
Iwo accelerometers were located in the
embankment, one at the crest, and one
in an abutment near the toe of the dam.
rhe exact locations are as follows:
No. A-1 Beneath the crest at Elevation
I 207.3 metres (680 feet).
No. A-2 Beneath the crest at Elevation
244.1 metres (801 feet).
No. A-3 Downstream toe, on rock at
Elevation 45.7 metres (150
feet) .
No. A-4 On the crest at downstream
edge Elevation 281.0 metres
(922 feet).
These instruments measured accelerations
.along three orthogonal axes: Vertical,
upstream-downstream (N46°E) and cross
canyon. In cooperation with the U. S.
Geologic Survey, (USGS) , three strong-
motion accelerographs were placed at the
site. One was located at the crest in
the same vault with A-4, one in the core
block gallery, and one on rock at Eleva-
tion 341.4 metres (1,120 feet) about 1.6
kilometres (1 mile) northwest of the dam
(Seismograph Station ORV) . The core-
block and crest instruments were orient-
ed as described above. The seismograph
station instrument was oriented with one
of the horizontal axes at N37°E. With
the exception of the core-block unit,
all strong-motion instruments were oper-
able during the 1975 earthquake activity.
All six dynamic pore-pressure cells in-
stalled in the upstream shell and transi-
tion zones showed a response during one
event or another of the August earthquake
series. The five groups of stress cells
were located in the downstream shell.
Each cell group measures stresses verti-
cally and at 45 degrees to vertical in
the upstream and downstream direction.
Each cell has two transducers; one mea-
sures both static and dynamic stresses
(CEC) , and the other measures static
stress only (MAIHAK) . Cell Numbers 1,
2, 5, 6, 7, 10, 11, 12, and 14 were op-
erable during the 1975 earthquake
activity.
Upgraded System
Following the August 1, 1975 Oroville
earthquake, the special consulting board
recommended improvements to the seismic-
data-acquisition system at Oroville. In
March, 1977, the system was upgraded by
adding new strong-motion accelerographs
at two stations on the dam crest, in the
grout-gallery adits on each abutment,
and in the core block. These five in-
struments were all connected to a trig-
ger at the toe of the dam and to a time-
signal receiver (WWVB) . In December
1978, the system was further upgraded
by replacing failed accelerometers and
pore-pressure signal-conditioning equip-
ment, and by connecting all but two sen-
sors to a digital recorder located in
the Area Control Center. However, the
dynamic soil-stress cells, which were
rendered inoperable by a lightning
strike at the dam in September 1976,
were not replaced.
The following is a detailed description
of the upgraded system as of December
1978 (Figure 109):
1. Installed four new SMA-IA strong-
motion accelerographs in the two in-
strument vaults on the crest, in the
left grout gallery portal, and in the
toe seepage vault. These replaced
existing SMA-1 units. These units
will provide film record of accelera-
tion at the unit and digital record
in the Area Control Center. (The two
existing SMA-1 units in the right
grout-gallery portal and core block
will provide film record at the unit
only) .
2. Installed three new FBA-3 force-
balance accelerometers. Two of these,
at the toe seepage vault and at crest
Station 53 instrument vault, replaced
failed units and provide redundancy
with the SMA-IA records, which are
on separate power supply. The third
FBA-3 was installed in instrument
house T on the downstream slope of
the dam at midheight. This unit is
a replacement for two existing FBA
units buried in the embankment. The
195
buried units were at the limit of
their life expectancy and were giving
questionable readings. All the FBA-3
units will provide digital record of
accelerations in the Area Control
Center.
3. Installed two EFM-1 earthquake force
monitors in the Area Control Center.
They are connected to the SMA-IA units
in the toe seepage vault and at crest
Station 53. They will display the
maximum acceleration experienced
6 - • PORE PRESSURE CELLS
3 - ■ ACCELEROMETERS
6- A STRONG MOTION ACCELEROGRAPH
(SMA-I OR SMA-IA)
since the last reset.
4. Installed new power-supply and cali-
bration - signal conditioning equip-
ment for the six pore-pressure cells.
5. Installed new DDS-1105 digital record
er in the Area Control Center, and
connected it to four new SMA-IA, thre
new FBA-3, and six pore-pressure cell.
All units are connected to a common
trigger. A common time base (WWVB)
will be recorded on all records.
CREST
AREA CONTROL
CENTER
N.W.S. ELEV. 274.3 m
(900 ft.)
CREST ELEV. 281.0m (922ft.)
ELEV. 45.7m (150 ft.)
FEET
METRES
Figure 109. Oroville Dam Embankment, Present Dynamic Instrumentation
(December, 1978)
196
3. RECORDED EMBANKMENT RESPONSE TO THE 1975 EARTHQUAKE
I General
If complete and clear records had been
obtained for the three or four larger
shocks of 1975, a rare chance would have
been available to test the mathematical
models used for dynamic analysis by com-
paring the computed response with the
observed response of the embankment.
Unfortunately, the recording system was
beset with problems and failures, and
only partial records were obtained for
the strongest shocks. One complete,
clear set of records was obtained - for
the September 27 aftershock.
The main use made of the records was to
estimate the natural period of the dam.
Secondarily, computed and recorded crest
motions were compared for the August 1
and September 27 events (Section 5).
These comparisons were complicated by the
three-dimensional effect of the canyon.
Recorded dynamic pore pressures in the
upstream shell and transition zones were
not significantly large. All dynamic
normal stresses were small.
Embankment response was evaluated for the
following events :
Epicenter
Distance
Seismic
Lat.
Richter
from dam
Depth
Event
Long.
Magnitude
(Km/mi)
(Km/mi)
Aug. 1
39° 26-33'
5.7
11/7
9/5.5
(main sho(
:k)
121° 31-71'
Aug. 5
39° 28-73'
121° 31-46'
4.7
7/4
9/5.5
Sept. 27
39° 30-65'
121° 32-69'
4.6
3.5/2
5.5/3.5
Many other foreshocks and aftershocks
were recorded but were not used in these
analyses.
For the August 1 and August 5 events,
there were gaps in the records during
the strongest shaking. However even if
records had been obtained during this
interval, they could not have been deci-
phered because of the overlap of adja-
cent records (Figures FllO and F112) .
The aftershock of September 27, produced
the only complete, clear records; how-
ever, the acceleration was of lower amp-
litude and higher frequency than the
first two.
Recorded Events
August 1, 1975
The DWR accelerometers were triggered by
a minor foreshock and were still record-
ing when the main shock occurred. With
the arrival of the large accelerations
of the main shock, other instruments
(pore pressure and stress cells) were
triggered, resulting in an overload and
a temporary loss of power. This loss of
power caused all of the instruments to
stop recording for most of the duration
of the strong motion. After several sec-
onds, the back-up power source was acti-
vated and all of the instruments started
to record again. The record is shown in
Figure 110.
197
RECORDER NO. I
r- Awi.i ■■"■ »m,-i^mi liuw
''''■^;.ZZ #>-^ii^
ELEV. 680, VERTICAL AiiM^IV^^^j^^^i^iiiKHiW
ELEV. 801, VERTICAL
ELEV. 580, TRANSVERSE tf^0h>ii>f**i'»ii^mim
ELEV. 801, TRANSVERSE ||^jp(tV^^.|Wliyii^»ii|«in
RECORDER NO. 2
TOE - UP AND
DOWNSTREAM
CREST - UP AND
DOWNS"!'REAM
fM\~^'
TOE — VERTICAL ►■V.V thiMimmttimMm
CEST-VERTICAL ^f^^^^\',iiKf\,^^*f'ly*t^^
TOE - TRANSVERSE V-«<V; ••.-<•-
ii 111 ' -/i
CREST - TRANVERSE
3T J/4iHMifeM8^?ifeli^
jy^^rVM^'*^^''*'*'*'!^^ 4 T Aj/%l^^^f^^
0 I 2 S 4 5
I ! 1 1 I t
TIME IN SECONDS
O iq
0 2g
VERTICAL SCALE
(ACCELERATION)
MAGNITUDE 5.7
Figure 110. Acceleration Records, Main Event of August I, 1975
198
Examination of aftershock records on re-
corder No. 2 showed the space between
two events to be about 1.5 centimetres
(0.6 inch), the same length as the gap
in the August 1 record. After August 8,
the speed of the recorders was increased
2-1/2 times. From then on, the space
between events was about 2.5 centimetres
(1 inch). Therefore, it was presumed
that the gap in the August 1 records
represented the distance the accelero-
meter drum rolled after power had been
cut off, and the time gap could not be
indicated correctly by the time scale
on the chart.
The power failure was reenacted to find
out how much time elapsed between main
power cutoff and activation of the back-
up power source. It was determined that
the generator, which is the source for
the back-up power supply, needed a mini-
mum of 5 to 6 seconds to start and sup-
ply power to the recorders once the main
power supply was cut off. Therefore,
the time gap in the main event record
was set at 6 seconds.
Recordings of stress for the August 1
event were also marred by a gap due to
the power loss. Before the gap, a maxi-
mum vertical normal stress of 159 kilo-
pascals (23 psi) was recorded by cell
No. 5. Pore pressure cell No. 1 regis-
tered a maximum pressure increase of 90
kilopascals (13 psi), which was dissipat-
ed during the 6-second gap. Pore-
pressure cells 4, 5, and 6 also showed
minor fluctuations, on the order of 14
to 34 kilopascals (2 to 5 psi) .
To gain an insight into what occurred
during the time represented by missing
portions of the DWR acceleration rec-
ords, USGS recordings of accelerations
at the seismic station and at the crest
of Oroville Dam were obtained and com-
pared with the corresponding DWR records.
Unfortunately, the first few seconds of
the USGS crest record were lost, as not-
ed in California Division of Mines and
Geology Special Report 124, "Oroville,
California Earthquake, 1 August, 1975".
However, the last portions of the DWR
and USGS crest records are nearly ident-
ical. Any differences are due to base-
line and instrument corrections per-
formed on the USGS record. The DWR rec-
ord was not corrected. The last portion
of the two crest records (following the
gap) can be lined up as shown in Figure
111. This leaves 2-1/2 seconds where
the record is missing from both the USGS
and DWR instruments.
The record at the USGS seismograph sta-
tion, 1.6 kilometres (1 mile) NW of Oro-
ville Dam, was positioned so that its
two highest peaks line up with the two
high peaks recorded on the DWR base ac-
celerometer. This positioning of the
USGS base record shows that the strong
base motion had essentially ceased by
the start of the USGS recorded crest mo-
tion. The USGS seismograph station and
dam crest records were digitized for use
in making analyses by computers.
August 5, 1975
As can be seen on Figure 112, the DWR
record again has a vital part of the
event missing and hence could not be used
in any subsequent analysis. It can be
seen, however, that like the August 1
recorded motions, the dam is freely oscil-
lating while the amplitudes of the accel-
erations of the crest are decreasing in
a typical decay curve patteim. This
again occurs with the amplitudes of the
recorded base motion being negligible.
The USGS does not have records of the
August 5 event.
September 27, 1975
The seismic event of September 27, 1975,
(Magnitude 4.6) was recorded in its en-
tirety on the DWR accelerometers. Figure
113. These records were digitized for
use in subsequent analyses. The digi-
tized records were processed using the
routine coii5)uter processing methods for
strong-motion accelerograms developed at
Cal Tech. Some changes, however, were
made in this standard processing tech-
nique. The instrimient correction was not
15—78786
199
DAM CREST, DWR A-4
N 46° E
5.0 TOO 15,0
TIME IN SECONDS
Figure 111. Acceleration Records with Corrected Time Scales
August 1, 1975
200
$^
TOE-UP AND DOWNSTREAM
CREST-UP AND DOWNSTREAM
'■'"'' ^" ' ^' * aJ^'^/;*^,/V^/V*vvA/^'^^w^
TOE - VERTICAL
CREST-VERTICAL
TOE - TRANSVERSE
|%l^^li^^W^^>'i^^^l^^y||||f^^lH>(>^lWl|lMl^
■K , ^ fl i CREST-TRANVERSE
«w«
7 5 10.0
TIME IN SECONDS
VERTICAL SCALE (ACCELERATION )
19:50 PST MAGNITUDE 4.7
Figure 112. Acceleration Records, Event of August 5, 1975
performed because the accelerometers are
of a force-balance type. It was assumed
that the instrument response was unaf-
fected throughout the frequency range of
interest .
The records of the base and crest mo-
tions (horizontal and vertical) were
baseline corrected and put through an
Ormsby filter to obtain equally spaced
acceleration points between 1.4 and 48
hertz. This filter bandwidth deviates
from the standard filter used at Cal
Tech, because of the high frequency con-
tent, low amplitude, and short duration
of the records. Acceleration-time his-
tories plotted from the digitized rec-
ords, along with corresponding response
spectra, are in Appendix B.
The USGS has no records of any seismic
events for September 27, 1975.
A maximum vertical normal stress of 62
kilopascals (9 psi) was recorded by cell
No. 5. Using methods which will be de-
scribed later, the vertical normal stress
computed for cell No. 5 location was 41
to 62 kilopascals (6 to 9 psi).
Observed Natural Period
For both the August 1 and August 5 events,
the dam continued to vibrate after the
earthquake had stopped. As shown in Fig-
ures 111 and 112, after the base accele-
rations had dropped to less than O.Olg,
long period crest accelerations continued
for several seconds, starting at an amp-
litude of about O.lg and decreasing in a
typical decay curve pattern for free
vibration.
For the August 1 record, 5 or 6 success-
201
in ,Lw. u , TOE- UP AND DOWNSTREAM
■ ' ' I'Mi! M i f| I I ^1 . (I . « . I*, /*, CREST-UP AND DOWNSTREAM
niMli
■Mi^v,H^J^m
TOE- VERTICAL
CREST-VERTICAL
TOE-TRANSVERSE
CREST-TRANVERSE
TIME IN SECONDS
0.2g 0.3g
VERTICAL SCALE (ACCELERATION)
14:35 PST MAGNITUDE 4.6
Figure 113. Acceleration Records, Event of September 27, 1975
ive cycles have periods close to 0.8
seconds. For the August 5 record, there
are 3 or 4 cycles in the decay curve with
a period of about 0.7 seconds. Accelera-
tion response spectra for the August 1
USGS crest record show a predominant
period of 0.8 seconds (Figure 114).
Response spectra were not calculated for
the August 5 event, because the extreme
overlap of adjacent records made accele-
rations indistinguishable for the strong
motion portions. The September 27 event
was not used for estimating period be-
cause it did not develop a clear decay
curve pattern for free vibration.
Since these observed periods are for free
vibration conditions, they are the natu-
ral periods of the dam; and since the
fundamental period is known to be domi-
nant in an earth dam, the observed per-
iods are presumed to be the fundamental
periods. Thus the fundamental natural
period is determined to be 0.8 seconds
for the intensity of shaking produced by
the August 1 main shock.
202
o
I-
<
cr
LU
_l
UJ
u
o
<
0.80I-
0.60
0.40
0.20 -
AUG. I, 1975
U.S.G.S. RECORD
AT DAM CREST
NOTE:
BASED ON RECORDED
ACCELERATIONS DURING
FREE VIBRATION ONLY
0.50 1.00 1.50
PERIOD IN SECONDS
2.00
Figure ]\h. Acceleration Response Spectra for Crest
Motions, Event of August 1, 1975
ANALYSIS OF STATIC STRESSES BY FINITE ELEMENT METHOD
General
The behavior of an embankment dam sub-
jected to dynamic loading by an earth-
quake is significantly influenced by the
stress condition existing in the embank-
ment prior to the earthquake. Current
methods of analysis for evaluating the
seismic stability and permanent deforma-
tions require knowledge of the static
stress distribution for the maximum sec-
tion of Oroville Dam. These static
stresses can best be calculated by the
finite element method, which permits the
evaluation of stresses and deformations
in an embankment through a series of
steps or increments to simulate construc-
tion and reservoir filling. The follow-
ing sequence was used in this analysis:
1. Construction of the core block in
four layers.
2. Construction of the cofferdam, up-
stream of the core block, in 14
layers.
3. Construction of the remaining embank-
ment in 27 layers.
4. Application of water load in four
stages, simulating filling of the
reservoir.
The finite-element representation of
Oroville Dam is shown on Figure 115.
This mesh, used in the static and dyna-
mic analyses, contains 564 elements and
585 nodes.
203
564 ELEMENTS
585 NODES
Figure 115- Finite Element Mesh, Maximum Section Oroville Dam
Material Properties
The success of finite-element analyses
to model the behavior of an earth dam
depends in a large part on how well the
nonlinear response of soil and rock ma-
terials under load can be described ana-
lytically. Because of the good compari-
son between observed and computed settle-
ments in a previous analysis by Kulhawy
and Duncan (1970), the same stress-straii
parameters were used in this analysis.
The difference between the parameters fo;
the transition (Zone 2) and shell (Zone
3) materials, shown in Table 5 is neglig-
ible. Therefore, Zone 3 parameters were
used for both Zones 2 and 3 in all the
finite-element-method analyses.
Table 5
Values of Stress-Strain Parameters
for Analysis of Oroville Dam
(From Kulhawy and Duncan)
Parameter
Values Used in Analyses
Symbol
Shell
Transi-
tion
Core
Soft ,
Clay^^
Concret
Unit weight (lb/ ft )
2
Cohesion (tons/ft )
Friction angle (degrees)
Modulus number
Modulus exponent
Failure ratio
Poisson's
ratio
parameters
150
0
43.5
3780
0.19
0.76
0.43
0.19
14.8
150
0
43.5
3350
0.19
0.76
0.43
0.19
14.8
150
1.32-^/
25.1^/
345
0.76
0.88
0.30
-0.05
3.83
a/
— Zone of soft clay at upstream end of core block.
hi — ?
— c and i for (a, +0,) <50 tsf; (c = 10.2 tons/ft ^
^ for (a + a ) >50
c/ Z
— Tensile strength of concrete = 14 tons/ft (200 psi) .
= 4»;
tsf)
125
0.3
13.0
150
1.0
0.9
0.49
0
0
162
216^/
0
137,500
0
1.0
0.15
0
0
204
Static Stress Analysis
Computer program ISBILD was used to car-
ry out the static-stress analysis. This
program is similar to the one used in
the earlier analysis of Oroville Dam by
Kulhawy and Duncan. The major differ-
ence is the type of element used. Kul-
hawy and Duncan used a quadrilateral ele-
ment divided into two triangles. Within
each triangle the strains vary linearly;
then, for compatibility reasons, the
strain along the sides of the quadrila-
teral element is kept constant.
Program ISBILD uses a quadrilateral in-
compatible isoparametric element. This
means that in addition to 8 regular de-
grees of freedom at 4 nodes, the element
has 4 internal degrees of freedom to im-
prove its bending behavior. These addi-
tional nodes of displacement, in general,
make the elements incompatible at the
interelement boundaries.
Seepage Forces
Reservoir effects are simulated by consi-
dering the water load in two parts:
total stress forces and water pressure
forces. To account for the effects of
the seepage forces in the core, piezo-
meter readings were used as input to the
computer program NODALFOR (developed by
Division of Safety of Dams). This pro-
gram uses the water pressures at nodes
and computes the forces at the sides of
elements due to these pressures. The
sum of these side forces is the result-
ant water force on the element. Result-
ant water forces are then distributed
to element nodes in proportion to the
contributing area of each node. The
values distributed to a node from adja-
cent elements are added to yield the net
water force at the node. This net water
force is added to the total soil force
(based on saturated unit weight) at the
node to get the effective soil force.
Table 6 shows the comparison between the
measured and calculated static stress
values .
Table 6
Static Stress Comparison
Direction
of Stress
Compressive Stress (tsf)
Cell No.*
Maihak Cell | FEM Analysis
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
13.8
29.5
14.4
30,
15.
22,
11.0
7.9
11.5
25.4
18.0
10.0
16.6
28.2
11.1
23.0
25.6
14.2
21.0
24.5
20.8
18.9
12.1
20.2
17.0
9.1
17.1
*Note: All but three of the
static stress cells
were functioning during
the 1975 earthquakes.
205
There is good agreement between measured
and calculated vertical stresses. In-
clined stresses, compression toward the
downstream toe, also show good agreement.
However, the two operable cells measur-
ing compression toward the upstream toe
measure only about half the calculated
stresses.
The computed static stresses in the
shells are compared with results by
Nobari and Duncan (1972) in Figures 116
through 119.
Stress comparisons are not valid in the
core because Nobari and Duncan present
total stresses, where the stresses
computed in this study are effective
stresses. Plots of stresses in all ele-
ments are included in Appendix C.
Figure 116. Contours of Effective Maximum Principal Stress in Oroville Dan
Ful 1 Reservoi r
CONTOURS ARE IN fsf
DEPARTMENT OF WATER
RESOURCES RESULTS
NOBARI AND DUNCAN RESULT
Figure 117. Contours of Effective Minimum Principal Stress in Oroville Dam
Ful 1 Reservoi r '
206
CONTOURS ARE IN T. S. F.
Figure 118. Contours of Maximum Shear Stress in Oroville Dam, Full Reservoir
DEPARTMENT OF WATER RESOURCES RESULTS _i_NOBARI AND DUNCAN RESULTS
I
NOT TO SCALE
Figure 119. Orientation of Principal Stresses
207
5. DETERMINATION OF DYNAMIC SHEAR MODULUS AND
DAMPING VALUES FOR EMBANKMENT SHELL MATERIAL
General
Dynamic shear modulus values at low
strains can be measured in the field us-
ing geophysical methods or in the labor-
atory using vibration tests. Values at
higher strains can be measured in the
laboratory using cyclic shear tests. If
recorded motions during an earthquake
are available, calculations can be made
to determine the modulus corresponding
to those recorded motions. Damping is
usually measured in the laboratory dur-
ing the same test used to measure the
modulus.
Measurement of dynamic shear modulus and
damping for the Oroville Dam shell mate-
rial is a difficult task: Field mea-
surements of shear wave velocity would
require deep borings in the gravel and
cobbles; undisturbed samples for labora-
tory tests would be next to impossible;
remolded samples for laboratory tests
cannot reproduce field conditions of
particle size, stress, time of loading,
or variability of grading and compaction
30000
10000
3000
1000
in the shell. In spite of the difficul-'
ties, a considerable effort was made to
determine the modulus and damping becaus(
they are the most important parameters
controlling the response of the dam to
an earthquake .
Studies by Seed and Idriss (1970) have
shown that the dynamic shear modulus of
granular soils can be related to the
effective mean normal stress as follows:
G = 1000 K2 (o'm)-'-''^
G = dynamic shear modulus in psf
K„ = a parameter relating G and a'm
am = effective mean normal stress
in psf
K„ is a function of strain level and
void ratio. K.
K„, is obtaine
(io-^%).
i"*!^'
the maximum value of
low shear strain
For clays. Seed and Idriss found that
shear modulus could be related to static
undrained shear strength and dynamic
shear strain as shown in Figure 120.
300
100
10"*
10-3
10-2 10-' I
SHEAR STRAIN %
AFTER SEED AND IDRISS (1970)
Figure 120. In-Situ Shear Moduli for Saturated Clays
10
208
It was presumed that the gravel shells
would dominate the response behavior
during earthquake shaking because they
occupy about 90 percent of the embank-
ment. Therefore, the testing and anal-
ysis for shear modulus were done only
for the gravel shell material. The
core modulus and damping were assumed
equal to published values for clays.
Two methods were used to determine the
modulus of the gravel shell material :
cyclic triaxial tests on remolded sam-
ples, and analysis of recorded embank-
ment response during the Oroville earth-
quakes of 1975. Damping values for the
gravel material were estimated from the
cyclic triaxial tests.
Cyclic Triaxial Tests
Laboratory test data to define the dyna-
mic properties of gravel material are
very limited. Presently available cyc-
lic test equipment can test specimens
up to 30 centimetres (12 inches) dia-
meter. The average gradation of the
Oroville shell material has a maximum
particle size of 15 centimetres (6
inches) and would require a specimen
diameter of 90 centimetres (36 inches).
Comparison studies by Becker, (1972)
have shown the same static strength for
samples with modeled gradation of 5 cen-
timetre (2-inch) and samples with field
gradation of 15 centimetre (6-inch)
U.S. STANDARD SIEVE SIZES
"200 '100
100
90
'50 "30
'16
3/8" 3/4" I 1/2"
70
50
40
liJ
O
(T 30
kJ
Q.
20
1
1
1
1
1
/
1 /
/
/
//
f
p
//
MODELED GRADATION FOR
/
f/
CYCLIC TRIAXIAL TESTS
1 1 1
^
1
/
/
//
/
AVERAGE FOR 24 TEST PITS
IN EMBANKMENT I964-I96€
1 1 1
1
r
5
I
7
r
li
ft
/
1
/
//
/
/
?
/
A
■-— PRC
1
)JECT AVERAGE
/
y^
1 i 1 J
^^
:::.=^_FIELD GRADATIONS
^
OROVILLE DAM, ZONE 3
1
<^^
1
1
1
1
i
1
0.1
0.5
1.0 5.0 10. 0
GRAIN SIZE IN MILLIMETERS
50.0 100.0
Figure 121. Sample Gradation for Cyclic Triaxial Tests
209
maximum particle size. It seems reason-
able to extend this kind of modeling to
cyclic testing.
A general study was undertaken by Wong
(1973) to determine the cyclic strength,
dynamic shear modulus, and damping of
gravels. Strain controlled cyclic tri-
axial tests of 30 centimetre (12-inch)
diameter samples of modeled Oroville
gravel gradation were part of that
study. Samples tested were composed of
Oroville gravel with 5 centimetre (2-
inch) maximum particle size and a grad-
ation curve parallel to the average
shell grading (Figure 121).
The sample density used was about 2 430
kilograms per cubic metre (152 pounds
per cubic foot) . Average density of
Zone 3 is 2 360 kilograms per cubic
metre (148 pcf ) . All samples were iso-
tropically consolidated with a pressure
of 196 kilopascals (4,096 pounds per
square foot).
Figure 122 shows the results of these
cyclic tests compared with the results
10"^ 10"
SHEAR STRAIN %
•0-- FROM FIELD SHEAR WAVE VELOCITY MEASUREMENTS,
SEED AND IDRISS 1970.
• TRIAXIAL TESTS ON MODELED OROVILLE GRAVEL BY WONG
MAXIMUM PARTICLE SIZE = 2 INCHES
SAMPLE DIAMETER = 12 INCHES
0-3C = 410 0 psf
RELATIVE DENSITY = 100%
SET UP DENSITY = 152 pcf
N = 5 CYCLES
■ FROM DYNAMIC ANALYSIS OF EMBANKMENT FOR 1975
RECORDED EARTH QUAKES ( PERI OD = ONE SECOND)
Figure 122. Modulus Determinations for Gravelly Soils
210
» DATA FOR OROVILLE MODEL GRADATION, THIS INVESTIGATION
AVERAGE VALUE FOR SANDS, FROM SEED AND IDRISS, 1970
— UPPER AND LOWER BOUNDS FOR SANDS
Figure 123. Comparison of Damping Ratios for Gravelly Soils and Sands
reported by Seed and Idriss. The Seed-
Idriss curves are based on field shear
wave velocity measurements for K„ ,
„ /„ , . 2max
and the average K»/K„ reduction curve
r J IT • 2^,2max ,
for sands. Usxng the same reduction
curve to fit the triaxial test data
gives a K„ value of 130.
Figure 123 shows the damping results
compared with the range of values for
sands reported by Seed and Idriss. The
test data points are very close to the
average curve for sands.
Analysis of Recorded Embankment Response
During the 1975 Earthquakes
General
Even though there were gaps in the rec-
ords of the stronger shocks, the 1975
Oroville earthquakes afforded an oppor-
tunity for analyzing embankment response
to determine the dynamic shear modulus
of the embankment materials. Accelera-
tion time histories were recorded at
both the base and the crest of the dam
for several events. The August 1 main
shock provided the best definition of
the natural period of the embankment -
the key to the analysis.
The natural period is dependent upon
stiffness (shear modulus) and mass dis-
tribution. Knowing the mass distribu-
tion and the period allows calculation
of the shear modulus. Knowing the shear
modulus and embankment strain allows
calculation of shear modulus parameter
K„
2max
Computer program QUAD4 was used in the
analyses. It determines the natural
period by solution of the eigenvalue
problem:
[K] =w^ [M] (5-2)
[K] = system stiffness matrix
[M] = system mass matrix
w = natural circular frequency
The stiffness matrix is developed from
211
UJ 300 1-
CHORD LENGTH = 5150 ft.
CREST ELEV. 281.0m (922ft.)
WITHOUT CAMBER
O.G.L
ESTIMATED DAM
FOUNDATION STRIPPING LINE
30*00 40*00 50*00
STATIONS (100 ft.)
DIVERSION TUNNEL NO. I
DIVERSION TUNNEL NO. 2 -
POWER PLANT ACCESS TUNNEL-i
PALERMO OUTLET WORKS
Figure \2h. Section on Long Chord of Dam Axis
the shear modulus values for all the ele-
ments in the maximum section FEM mesh
— and is therefore a function of shear
modulus parameter K„ .
The Oroville embankment is located in a
triangular canyon and has a crest length
to maximum height ratio of approximately
7. A longitudinal profile is shown in
Figure 124.
A three-dimensional (3D) analysis of the
dam to determine K„ of the gravel
shell material is not possible, because
present computer capabilities are inade-
quate for dams as large as Oroville.
The solution to this problem is to find
the appropriate values of natural period
and shear strain to use in a two-
dimensional (2D) analysis.
Makdisi (1976) has derived a relation-
ship between the natural periods comput-
ed by 3D and 2D analyses for a 30-metre
(100-foot) high dam with slopes of 2:1
and a constant shear modulus throughout.
Assuming this relationship is valid for
the much higher Oroville Dam with vari-
able shear modulus as defined by equa-
tion 5-1, the 2D period can be computed
corresponding to the observed period in
the August 1, 1975 earthquake.
The same value of shear modulus, G, was
used in the 2D and 3D analyses in deriv-
ing the natural period relationship.
Since the parameter to be calculated,
G , would have to be the same for 2D
and 3D, then G/G and consequently the
shear strain are also the same for the
2D and 3D cases. Thus the same strain
and modulus reduction factor must be
used for the 2D and 3D analyses when
applying the natural period relationship
1
TRIANGULAR CANYON
H = I00 FEET
SLOPES = 2:|
Vs = 500 fps
AFTER MAKDISI, 1976
OROVILLE DAM L/H=7
I 35
Figure 125. Comparison of Natural Period;
for Two- Di mens ional and Three-Dimens ioni
Embankment in Triangular Canyon
212
It is important to note that this rela-
tionship would not give the correct per-
iod for a very long (2D) dam subjected
to the August 1, 1975 earthquake shaking.
But it does give a correct relationship
among period, strain, and K„ , allow-
ing the calculation of K„
2max
Natural Period for Two-Dimensional
Analysis
Makdisi's correlation of 2D and 3D per-
iods only goes to an L/H of 6. Extra-
polating to an L/H of 7 gives a period
ratio of 1.25 to 1.35 (Figure 125). The
natural period of Oroville Dam Embank-
ment in the August 1, 1975 earthquake
was estimated to be 0.8 seconds (see
page ) . The natural period range to
be used in the 2D analysis is 1.0 to
1.1 seconds.
Shear Strain for Two-Dimensional
Analysis
The maximum displacement computed from
the August 1 recorded (USGS) crest mo-
tion is 1.5 centimetres (0.6 inch). The
assumption is made that the peak shear
1.0
strain (y max) is constant throughout
the dam and is equal to maximum crest
displacement (D) divided by embankment
height (H) .
Y max = I X 100% = 0.007%
A ratio of average strain to peak strain
of 0.6 has been used in this study.
Thus the average shear strain is about
0.004 percent for the actual (3D) dam,
which is also the value to use in the
Two Dimensional Analysis.
Shear Modulus Reduction Factor
The average shear modulus reduction
curve for sands shown in Figure 126 was
used for the gravel shells. At a shear
strain level of 0.004 percent, the modu-
lus reduction factor is 0.86. This val-
ue agrees well with the results of a
dynamic response analysis for the Aug-
ust 1, 1975 earthquake, which will be
discussed later in this chapter. The
range of reduction factors in that anal-
ysis was generally only 0.78 to 0.88.
An average value of 0.85 was used in the
calculation of K„
2max
2
^ .4
^
*^
^
^
c
ORE-
K
' ^
\i
^
N
)
V
^^
N
s^
V
-SHE
LL
* ■i.)i.
\
^
^
fc=*
^==t\
I0'2 10"'
SHEAR STRAIN %
-D- AVERAGE REDUCTION CURVE SANDS, FROM SEED AND IDRISS
-O- AVERAGE REDUCTION CURVE CLAYS, FROM SEED AND I DR ISS
-z^ REDUCTION CURVE CLAYS, Su = 8000 psf FROM SEED
(PRIVATE COMMUNICATION)
Figure 126,
Soi Is
Shear Modulus Reduction Curve for Embankment
213
(J)
LlI
20
< —
^
^
A
s
0
80
20 40 60
NORMAL STRESS ( tsf )
Figure 127. Static Shear Strength Envelopes for Core
Material
^2max
vs. Natural Period
Computer program QUAD4 was used to cal-
culate natural periods for the follow-
ing input properties and conditions :
A. Finite element mesh of Maximum Sec-
tion (Figure 115)
B. Static stresses determined from
static FEM analysis
C. Shell and Core Material Densities
used in static FEM analysis
D. Core shear modulus - three trial
values of G /S - 1100, 2200,
4400 "'^^ "
- CU shear strength envelope
(Figure 127)
E. Shell K^jj^^^ _ jQ^^ ^^^^^ values -
100, 200, 300, 400
F. Shear Modulus Reduction Factor for
both shell and core - 0.85
The results are plotted in Figure 128
as a family of curves of K„ vs. nat-
. , ^ , . 2max . . -
ural period. Each curve is for a dif-
ferent value of core modulus. Varying
the core modulus by a factor of four
changes the shell K- by 20 percent
to 25 percent.
Range of K„ - The range of K„ is
135 to 210 for a natural period from 1.0
second to 1.1 second and core Gmax/Su of
1100 to 4400.
Comparison of Observed and Computed
Crest Motions
Ideally, the value found for shell
^2max ^°"-'-'^ ^^ used in a three-
dimensional dynamic analysis using the
recorded base motion. A comparison of
the computed crest motion with recorded
crest motion would then be a direct
check on the mathematical model and
material properties used. However, a
three-dimensional analysis is not pres-
ently possible for Oroville Dam, and a
"1 1 1 1 1 1 1 1 I I r
= 0 85
I I
▲ Gm»x /S„ = 1100
• Gm«k /S^ - 2200
■ G„„ /Su = 4400
FROM CU STRENGTH ENVELOPE
I I I
NATURAL PERIOD (SECONDS)
Figure 128. Ko vs. Natural Period
^ 2max
214
two-dimensional analysis woulci give a
different response acceleration as shown
by Makdisi (Figure 129) . His study was
done for a 30 metre (100 feet) high dam,
Taft earthquake, and L/H =3. In some
locations particularly at the crest, the
difference is large — up to 100 percent.
This is because the restraint or stiff-
ening effect of the abutments is ignored
in a plane strain analysis. Therefore,
the two-dimensional analysis needs to be
modified to account for the abutment
restraint.
L/H = 3
Vg = 500 fpS
0.98g
p -- 0.10
0.54g
o
o
0.66g ^^\ 0.53^3-D
0 40g" •^^v^.29^ Plane Strain
0.229 , 0.22g ^^~^^
O.I6g ' 0.2lg
O.2I9
*^v^22g
///mw<^.
0.2g
MID-SECTION
0.39g
0.53g
0.32g
0.3g
0
10
0.43g
*"~-^.36g
O.I9g
0.2! g
1
O.I9g^^^^^
*0.2lg
O.ISg
\^2g
/U^//A^\.\
0.2g
QUARTER SECTION
Figure 129. Maximum Accelerations Computed from 3D and Plane Strain
Analyses Using Base Motions from Taft Record (After Makdisi)
215
Embankment Response Model
The Embankment Response Model is a two-
dimensional analysis with a modified
Ko (pseudo K„ ) value that gives
2max '^ , ^ 2max . , , ° ^, „
a computed natural perxod equal to the
observed period (3D) for the actual em-
bankment during the August 1, 1975
earthquake. It is an implied assumption
that the same adjustment which accounts
for the three-dimensional effects on
natural period will also account for the
three-dimensional effects on acceleration
and strain. The pseudo K^ value is
higher than the K™ represeucing sheat
modulus because the stiffening or re-
straint effects of the abutments are
included.
By definition, the model applies to the
August 1, 1975 earthquake. This same
model may apply to other, stronger.
earthquakes, but the 1975 earthquake
series did not provide enough informa-
tion to test this question.
The value of pseudo K^ corresponding
to the observed natural period of 0.8
sec. is 285 to 370 (Figure 128).
August 1 Event
The acceleration record at the toe of
the dam was not usable because of the
six-second gap. The bedrock record froit
seismograph station DRV was used, even
though it is a mile from the dam, 275
metres (900 feet) higher in elevation,
and oriented 9 degrees different than
the dam instruments. Where both records
are present, accelerations are similar
for seismograph station DRV and the toe
of the dam. Other input was as follows;
Computer Program LUSH
Highest Frequency Used 8 Hertz
Shell - Pseudo K^ 350
- Average Modulus Reduction Curve for Sands
(Figure 126)
- Average Damping Curve for Sands (Figure 130)
Core - G /S 1750
- Shear Strength Envelope UU
- Higher Modulus Reduction Curve for Clays (Figure 126)
- Average Damping Curve for Clays (Figure 130)
Poisson's Ratio
0.3
The comparison between the computed and
observed crest accelerations is shown in
Figure 131 along with the input bedrock
motion. Comparisons of displacement
time history and acceleration response
spectra are shown in Figure 132. The
shapes and magnitudes of the computed
patterns are generally similar to those
observed. The response spectra of the
computed crest motion show the dam to
oscillate with two distinct periods.
The first period of 0.15 seconds is not
evident in the response spectrum of the
observed crest motion, probably because
the period of 0.15 second corresponds
to the forced vibrations during base
shaking, which is the missing portion
of the crest record. The second period
shown in the response spectrum of the
computed crest motion occurs at 0. 75
seconds, slightly different from the
period of 0.8 seconds for the recorded
motion. This may mean that 350 is too
high a choice for pseudo K„ , or that
216
35
30
15
10
/'
A
Y
t
X
/
SHEL
L '
r
/
/
/
/
/
•—CORE
1
X
^
I f
r
C-l (
f=^
F^
r^
>
.} >
10"
10-^ I0-'
SHEAR STRAIN %
-O- AVERAGE DAMPING CURVE SANDS, FROM SEED AND IDRISS
-O- AVERAGE DAMPING CURVE CLAYS, FROM SEED AND IDRISS
Figure 130. Damping Ratios for Embankment Soils
the frequency content was different for
the bedrock motions at the base of the
dam and at seismograph station ORV.
September 27 Event
The bedrock motion of the September 27
event recorded at the dam toe was used
as input to the dynamic finite element
model. Other input was the same as for
analysis of the August 1 event, except
the highest frequency used for LUSH was
16 Hertz instead of 8 Hertz.
Response was computed at the crest and
at 74 metre (240 foot) depth. Compari-
sons of computed and observed accelera-
tion time histories and response spectra
are shown in Figure 133.
Accelerations at the crest are much
smaller than in the August 1 main shock,
and the duration of shaking is much
shorter. The response is all at high
frequency — 2 to 10 hertz. Either the
shaking is not strong enough to excite
the dam into definitive free vibration
motion, or the fundamental period is
much smaller for the September 27 event.
Dynamic Properties Adopted for the
Gravel Shell
The shear modulus parameter, K„ , was
determined for the gravel shell ^y
cyclic triaxial tests and analysis of
embankment response to the August 1,
1975 earthquake. Both methods have
serious limitations including:
1. Remolded samples cannot faithfully
model variations in gradation and
compaction in the embankment.
2. The triaxial test does not correctly
model the stresses in the embankment.
3. Shear strain is assumed constant
217
throughout the dam in the analysis
of observed response.
4. Makdisi's correlation for natural
periods was developed for a 30 metre
(100 foot) high dam with constant
shear modulus and daiQping throughout.
This correlation was assumed applic-
able to Oroville Dam with a height of
230 metres (750 feet) and a shear
modulus that varies throughout.
The two different methods gave different
answers. However, these results bracket
published values for dense gravels
(Figure 122). Therefore, it was decided
to use two values, 130 and 205, to rep-
resent the range.
Because the damping results determined
in the cyclic triaxial tests agreed so
well with the published average values
for sands, it was also decided to use an
approximation of the average damping
curve in computing dynamic stresses
generated by the Reanalysis Earthquake.
COMPUTED RESPONSE AT CREST
(NODE 4)
SHELL PSEUDO Kjmax^^SO
CORE Gmax/ Sy ^ '"^50
A/Vr^^\jJ\A/\p^ 'A.y^'\j\
STARTING TIME CHOSEN TO GIVE BEST
MATCH OF OBSERVED ANDCOMPUTED RESPONSE
'|VAy^\K^"VV^\''^'\^v^"'.V..-..vV-..^..-vJ\.
INPUT AT BASE
(USGS)
SEISMOGRAPH STATION ORV
( I MILE FROM DAM )
O-OO 1.00 2.00 3.00 q.M 5.0O S.OO 7.00 8.0O 9.00 10.00 11.00 12. TO
TIME [SECONDS!
Figure 131. Comparison of Acceleration Time Histories, August 1 Main Shock
218
FROM OBSERVED CREST ACCELERATIONS
FROM COMPUTED CREST ACCELERATIONS
COMPUTER PROGRAM LUSH
SHELL PSEUDO Kjmax-SSO
CORE Gmax/Su=I750
CURVE FOR OBSERVED DISPLACEMENTS LOCATED
TO GIVE BEST MATCH WITH COMPUTED DISPLACEMENTS
ACCELERATION RESPONSE
SPECTRA FOR CREST MOTIONS
ACCELERATION RESPONSE SPECTRA FOR
BASE MOTION USED IN LUSH ANALYSIS
OBSERVED
COMPUTED
5 % DAMPING
'^.oo
5% DAMPING
'^.oo
Figure 132. Comparison of Displacement Time Histories and Acceleration Response
Spectra for Crest Motions, August 1 Main Shock
219
COMPUTED
0.10-
ACCELERATiON RESPONSE SPECTRA
»- 0 1.0 2.0 5.0 4.0
c TIME IN SECONDC
ui
OBSERVED
-O.IOt
O.IO
o
OB SERVED
COMPUTED
1.00
PERIOD IN SECONDS
0 !.0 2.0 3.0 4.0
TIME IN SECONDS
NODE 4 ICREST) ELEVATION 922 FEET
COMPUTED
ACCELERATION RESPONSE SPECTRA
^-.rMj\J^Jy\^
-o.;o|
0 1.0 2.0 3.0 4.0
TIME IN SECONDS
OBSERVED
Z 0.40-
O
I-
< ,
Q^ 0.20-
\il
_l
liJ
o
<
OBSERVED
COMPU'^ED
5% DAMPING
0.50
1.00
PERIOD IN SECONDS
220
0 1.0 2.0 3.0 4 0
TIME IN SECONDS
NODE 88 ELEVATION 680 FEET
Figure 133. Comparison of Acceleration Time Histories and Response Spectra,
September 27 Aftershocks
REANALYSIS EARTHQUAKE
On August 1, 1975, a Magnitude 5.7 earth-
quake occurred approximately 12 kilo-
metres (7.5 miles) southwest of Oroville
Dam. The associated surface cracking,
traced to within 5 kilometres (3.1 miles)
of the dam, revealed a previously uniden-
tified "active" fault (see Figure 134) .
For a more detailed discussion, refer to
Chapters II, III, AND IV of this bulle-
tin, which describe geological and
seismological studies as well as vert-
ical and horizontal geodesy.
Historically, other local events include
the following earthquakes:
Richter Magnitude
5.7
4.7
4.7
4.7
Date
February 8, 1940
May 24, 1966
April 29, 1968
August 1, 1975
Location from Dam
50 km (31 miles) north
37 km (23 miles) northwest
48 km (30 miles) west
14 km (9 miles) southwest
In addition, other known faults and
maximum credible earthqxiakes are as
follows :
Fault Richter Mag.
San Andreas 8.5
Honey Lake 7 . 5
Mohawk Valley
Bear Mountains - Melones
Distance from Dam
195 km (122 miles)
117 km (73 miles)
72 km (45 miles)
58 km (36 miles)
See Figure 135 for fault locations.
Based on the hypocenter locations of the
August 1 main shock and the subsequent
aftershocks, the causative fault was de-
fined as dipping to the west from the
ground surface cracking. This fault
system is presumed to extend northward
beyond the limit of identified surface
cracking. Thus, as illustrated in
Figure 136, at depth it would pass
directly under Oroville Dam.
The main shock hypocenter was about 9
kilometres (5.5 miles) deep; the after-
shock hypocenters were 3 to 8 kilometres
(2 to 5 miles) deep. It is assumed for
purposes of developing Reanalysis Earth-
quake motions, that for an earthquake
larger than magnitude 5.7, the hypocen-
ter would be 5 kilometres (3 miles) from
the base of the dam.
In view of the 1975 earthquake activity,
the Consulting Board for Earthquake
Analysis and the Special Consulting
Board for the Oroville Earthquake rec-
ommended the following:
A. "In view of the developments, it is
appropriate to consider that earth-
quakes ranging up to magnitude 6.5
may occur within a few miles of the
dam site."
B. "The Board considers that an appro-
priate earthquake motion for reeval-
uation of structures critical to pub-
lic safety in the Oroville-Thermalito
complex would be one producing a peak
acceleration of 0.6g and having char-
acteristics similar to those developed
near Pacoima dam during the San
221
Photo lineoment
•• ■ Probable Fault
— V~^ Fault, dip indicoted
if known
• Epicenters
s
l_l_L
0
1 1 1
MILES
5
1
10
KILOMETRES
Figure 13^. Lineaments, Faults and Recorded Epicenters Around Oroville
222
FAULT
INFERRED FAULT
I I I I — I — u.
MILES KILOMETRES
Figure 135. Location of Faults in Relation to Oroville Dam
223
SURFACE CRACKINGn
^^^'^ OROVILLE DAM — -^'"^^ >*L^^^ |
/ i
/
/
+
4-
/
+
4 4
+
. /
+
4
+
+
+
/ + +
4
4 4 +
4
4-
/
4^ -%
4
4
/
FAULT PLANE ASSUMED
/^
TO GO THROUGH SUR-
HYPOCENTER FOR MAIN SHOCK
r^
FACE CRACKING AND
HYPOCENTER OF
DATE, AUG-I , 1975, TIME 13^20 PDT
/
MAIN SHOCK
MAGNITUDE 5.7, DEPTH 8.8 ""^--^
KILOMETRES ^ ^
\
/
CROSS SECTION AT MAIN SHOCK HYPOCENTER
PROJECTED NORTHWARD 10 KILOMETRES
4- DENOTES ESTIMATED HYPOCENTER FOR EARLY AFTERSHOCKS,
AUGUST I THRU 7, 1975
I 1/2 0
I I I I 1_
_1 I
MILES KILOMETRES
SECTION BEARING EAST-WEST
Figure 136. Relationship of Oroville Dam to Assumed Northward Extension of
Faul t
224
Fernando earthquake of February 9,
1971. The time-history of such a
motion should be obtained from a
modified form of the Pacoima dam
record, as discussed in the "Report
of the Consulting Board for Earth-
quake Analysis" dated May 22, 1973.
The actual time-history could be the
same as that forwarded to Mr. Jansen
by Clarence R. Allen with his letter
of January 16, 1974, except that the
duration of shaking should be limit-
ed to the first 20 seconds of the
record provided, and all ordinates of
the record should be multiplied by a
suitable scaling factor to give a
peak acceleration of 0.6g.
"In addition the structures should
be checked for the motions produced
by the following earthquakes :
(a) a magnitude 8.5 earthquake oc-
curring at a distance of 161
kilometres (100 miles)
(b) a magnitude 7.25 earthquake oc-
curring at a distance of 56 kilo-
metres (35 miles)
It is unlikely that these latter two
earthquakes will produce conditions
more critical than the motion dis-
cussed in detail above, but the check
should be made to verify that this is
so. Design earthquakes for noncrit-
ical structures can be less severe
in intensity than those discussed
above, and the Board will defer this
recommendation vintil the evaluation
of critical structures is completed."
Ground motion characteristics are esti-
mated for the recommended earthquakes as
follows (Figure 137) :
Magnitude
Distance
Km/Mi
Peak
Acceleration
Predominant
Period
Sec.
Duration
(a > .05g)
Sec.
6.5
7.25
8.5
5/3
56/35
161/100
0.6g
0.15g
0.05g
0.29
0.4
0.8
20
23
3
Based on these characteristics, the
ground acceleration for the nearby event
of magnitude 6.5 exceeds that from the
others; and the duration is generally as
great or greater; therefore, the 7.25
and 8.5 magnitudes will not be considered
further in the analysis.
The acceleration time history shown in
Figure 138 is essentially the one recom-
mended by the consulting board. The
accelerogram was derived by scaling the
Pacoima S16E record down by 0.6/1.17 and
adding the Taft record scaled up by
0.3/. 15. The first 2.6 seconds of the
Taft record were dropped and the joining
made at time 11.2 seconds of the Pacoima.
Accelerations in the Taft portion are
about 30 percent higher by this proce-
dure than by scaling all ordinates of
the time history provided by Clarence R.
Allen, to give a peak acceleration of
0.6g. However, the Taft portion peaks
are still small in comparison to the
Pacoima peaks, and do not produce signi-
ficant stresses in the embankment. The
resulting Reanalysis Earthquake has the
following characteristics:
Richter Magnitude
6.5
distance from energy 5 kilometres
source to dam (3 miles)
maximum acceleration 0.6g
predominant period 0.4 seconds
duration
acceleration time
history
20 seconds
modified Pacoima
plus modified
Taft
Figures 138 and 139 show the accelera-
tion time history and response spectra.
225
40
60
KILOMETRES
80 100 120
140
.8
rv
1
. r
Z
o
.6
1-
<
(T
fi
UJ
_J
UJ
4
tJ
o
<
.3
2
-)
s
. 2
X
<
. 1
. 1
1 1
1
1 1
1 1
1
A \N
\ \ Xv'^
\4f \£rr<^
;::::>..^
X2^
^-^^
MAXIMUM ACCELERATION
AFTER SCHNABEL AND SEED "ACCELERATIONS IN ROCK FOR EARTH-
QUAKES IN THE WESTERN UNITED STATES" BULLETIN SEI S MO LOG ICAL
SOCIETY OF AMERICA, VOLUME 63,1973
PREDOMINANT PERIOD
AFTER SEED, IDRISS AND KIEFER, "CHARACTERISTICS OF ROCK MOTIONS
DURING EARTHQUAKES" JOURNAL, SMFE, SEPT., 1969.
C/5
a
40
H
O
o
35
UJ
C/1
30
25
<
20
:d
Q
15
Q
UJ
t-
10
UJ
^
o
b
<
cc
CD
0
\V
"^§S|
^^M = 8
V 1
^
a> 0.0
5g
^^
V
f > 2 h
z
x^.
\\
\
w
\
\^-
\N
^
1
>.-,^^^^
==:,J2II
_i ^ \ —
- ^ -
=__::^=
20 40 60 80 100
DISTANCE FROM ENERGY SOURCE-MILES
120
BRACKETED DURATION
AFTER BOLT "DURATION OF STRONG GROUND MOTION" PROCEEDINGS
FIFTH WORLD CONFERENCE ON EARTHQUAKE ENGI N EER I NG , ROME, I 974.
Figure 137. Earthquake Ground Motion Characteristics
226
8.00 lO.OO
TIME (SECONDS)
Figure I38. Reanalysis Earthquake
227
2. so 3.00
Figure 139- Response Spectra for the
Reanalysis Earthquake
228
J
7. ANALYSIS OF DYNAMIC STRESSES FOR THE REANALYSIS EARTHQUAKE
Methods of Response Computation
The response of a multiple-degree-of-
freedom structure may be determined by
solution of the following set of
equations:
[M] (u) + [C] {ui + [K] fu} = F(t)
[''] = lEass matrix for the structure
[C] damping matrix for the structure
[K] = stiffness matrix for the
structure
u, u, u = nodal accelerations, veloc-
ities, and displacements
F(t) = earthquake load vector.
Two of the most commonly used programs
in the United States for solving these
equations are QUAD4 (Idriss, et al,
1973) and LUSH (Lysmer, et al, 1974).
Both of these programs are currently in
use in the Department of Water Resources
for computing the seismic response of
finite-element models of embankment dams.
Some modifications have been made to them
so the LUSH will generate stress time
histories, as well as acceleration and
displacement time histories, and QUAD4
will take input in the same format as
LUSH.
Both programs use the equivalent linear
method to account for the nonlinearity
in the soil shear modulus and damping
ratio. Every element in the structure
is assigned an independent value of
damping ratio and shear modulus, depend-
ing upon the average shear strain anti-
cipated during the earthquake. These
properties remain constant during the
shaking. After the response has been
computed, the average shear strain and
corresponding soil properties for every
element are evaluated. If the differ-
ence between the assumed and computed
soil properties is less than a given
tolerance, the solution is assumed con-
verged. The average shear strain is
computed as a fixed fraction of the
maximum shear strain experienced during
the shaking.
QUAD4 solves the equations of motion by
a direct integration method. Integration
may be carried out by either the linear
acceleration technique or Wilson's Theta
Method. Rayleigh damping is used which
filters out the structure's response in
the higher frequency range.
LUSH uses a complex number formulation
of the elastic moduli and a method of
complex response which assumes that the
input motion is harmonic. This formula-
tion allows viscous damping to be intro-
duced in the construction of the stiff-
ness matrix. The program was developed
to analyze the response of high-frequency
structures, such as nuclear power plants,
and has the advantage of providing a more
accurate response and a faster solution
time.
Acceleration Response of Dam to
Reanalysis Earthquake
Acceleration time histories were comput-
ed at four elevations in the embankment
for the following conditions:
Coii5)uter Program
Shell K„
2max
QUAD4
130
Core Shear Modulus
G /Su
max
2200
Undrained Strength
Envelope
CU
Average Shear Modulus
Reduction Curves and
Damping Curves
Poisson's Ratio
0.3
Figure 140 illustrates how the motions
are modified in progressing upward
through the dam.
229
4.0
TIME IN SECONDS
8.0 12.0 16.0 20.0
0.50
0.50
0.25
0
z
9. 0.25
H
<
(£
1^0.25
UJ
^ 0
<
■d 0.25
Z
o
N
S 0.25
O
^ 0
0.25
0.50
W«
*f^fltgri
IhE
iwtf
^
i
uimE
VATtON ?.QQ '^EIX
,Y$1
':?^'^:f
^7
P^™#'
int
mm_
TFTfrofK
»
#te
8.0 12.0 16.0 20.0
TIME IN SECONDS
Figure 140. Acceleration Response to Reanalysis
Earthquake
230
Input Variables and Computed Shear
Stresses
Comparative studies were made to eval-
uate the influence of several variables
on computed shear stresses. Two comput-
er programs, LUSH and QUAD4, were used
for the dynamic stress analyses. Both
programs are in general use for comput-
ing dynamic shear stresses of
embankments.
Shear stresses were calculated for two
values of K^ for the shell — 130 and
205. These values were considered to
represent a reasonable range for the
highly compacted gravels. The 130 value
was determined by cyclic triaxial tests
on 30 centimetre (12-inch) diameter sam-
ples of gravelly sand with 5 centimetre
(2-inch) maximum particle size. The 205
value was chosen to represent the upper
limit of the range estimated by a two-
dimensional analysis for observed crest
motions in the August 1, 1975 earthquake.
Two of the soil properties used in the
analysis, namely shear modulus of the
core and Poisson's ratio, were assumed
based on published information for other
soils. Therefore, stresses were calcu-
lated for a range of values of these
properties to determine their influence
on shear stresses.
Although most of the study was concen-
trated on the maximum section of the dam,
shorter abutment sections could be more
critical. Consequently, dynamic shear
stresses were also calculated for dam
sections 100 metres (330 feet) high and
64 metres (210 feet) high.
The following table summarizes the dif-
ferent values used in the comparison
studies :
Variable
Shell Shear Modulus
Paramater K„
Core Shear Modulus
Parameter G /S
Shear Strength Envelope
Modulus Reduction Curves
Computer Program
Poisson's Ratio
Embankment Section
Values Used in Comparison Studies
130
Low
2200
CU
Low*
QUAD4
(Wilson's Theta Method)
(.02 second time step)
0.3
750 ft.
205
High
1120
UU
High*
LUSH
(Highest frequency =
8 Hertz)
0.45
330 ft.
.3/. 49**
210 ft.
*The modulus reduction curves and damping curves used are shown in Figures 20 and
24. The low-modulus reduction curve for clays is the average curve by Seed and
Idriss. It is generally for low values of Su. The high-modulus reduction curve
for clays was provided by Professor Seed to John Vrymoed. It is for an S of
8000 psf. It was used for core elements with S greater than 6000 psf.
**0.3 in unsaturated downstream zone
0.49 in submerged upstream zone
17—78786
231
Appendix E includes plots of maximum
dynamic horizontal shear stress and
shear strain for the several conditions
studied, shear stress time histories for
K_ of 205 and 130, and acceleration
timl^istories for K. of 205 and 130.
/max
The following embankment properties and
conditions were held constant for all
analyses :
Acceleration time history for Reanalysis
Earthquake
Shell
- moist density 150 pcf
- saturated density 153 pcf
- average modulus reduction curve for
sands
- average damping curve for sands
Core
- saturated density 153 pcf
- average damping curve for clays
Core Block
- density 150 pcf
- constant shear modulus 187,200,000
psf
- constant damping
Static stresses from static finite ele-
ment method analyses.
Influence of Shear Modulus of Shell
Material
Response analyses were conducted for twc
values of K„ ^ , 130 and 205, as dis-
cussed previously (page 214). The fol-
lowing embankment properties and condi-
tions were used for both analyses:
Computer Program LUSH
Maximum Section
Poisson's Ratio 0.3
Core - G /S = 1120
max u
- UU static shear strength
envelope
- Higher shear modulus reduction
curve for clays
Table III shows the average maximum shea
strains throughout the embankment.
Table III
Shell
2max
Average Maximum
Shear Strain (%)
130
205
0.18
0.09
Average shear strain = 0. 6 x maximum
shear strain.
Iterations continued until computed G
was within 10 percent of trial G in
nearly all elements.
OROVILLE DAM - MAXIMUM SECTION
REANALYSIS EARTHQUAKE— MAXIMUM ACCELERATION =0.6g
LUSH DYNAMIC RESPONSE ANALYSIS
CORE
Su
1120 (HIGHER CORE MODULUS
Increasing the modulus from 130 to 205
increases the shear stresses by 20-70
percent in the lower portion of the up-
stream shell as shown in Figure 141.
Unfortunately, comparisons were not pos-
sible in the upper portion of the dam
because LUSH stresses for K^ of 130
, . 2max
were xncorrect in this area Xsee section
on computer programs).
MAXIMUM AT,, (K,
^205)
MAXIMUM AT C K,
= 130)
STRESSES FOR K
2 MAX
INCORRECT IN UPPER 300 FEET
Figure 1^1. Influence of Shear Modulus of Shell Material on Computed Maximum
Horizontal Dynamic Shear Stresses
232
Influence of Shear Modulus of Core
Material
A comparison of maximum dynamic shear
stresses was made for two sets of core
modulus input data. Both analyses were
made using the following embankment pro-
perties and conditions:
Computer Program LUSH
Maximum Section
Shell K = 130
Poisson s Ratio =0.3
The two sets of core modulus parameters
were as follows :
Core Material
Parameter
Figure
120
High Core Modulus
1120
(Lower bound value
reported by Seed &
Idriss, 1977)
Low Core Modulus
G /S
max u
2200
(Average value
reported by Seed
Idriss, 1977)
Undrained
Strength
Envelope
127
Unsaturated
UU
(End of construction
condition)
Saturated
CU
(End of embankment
consolidation
condition)
Normal Stress
Modulus
Reduction
Curve
116
126
l/2(a' lc+ a'3c)
(From static FEM
analysis this study)
Higher curve for most
elements because
S = 6000 psf or more
l/2(a'ic +a'3c)
(From static FEM
analysis by Nobari
and Duncan, 1972)*
Lower curve for all
elements because S
generally less than
6000 psf
*Normal stresses by Nobari and Duncan were used because their finite element mesh
was finer in the core and transition zones than the mesh used in the present study,
and the stresses were therefore better defined. However, after the analysis was
completed it was discovered that these were total stresses, not effective stresses.
Their figures 67 and 68 incorrectly defined the plotted contours as effective
stresses. The net result is" that the low core modulus is somewhat higher than
intended, but still four times less than the high core modulus.
Of the listed parameters, the undrained
strength envelope and modulus reduction
curve were most significant. The CU
strength envelope gave Su values about
half as great as the UU envelope, gener-
ally less than 8000 psf. This, in turn
caused the lower reduction curve to be
used which has about four times as much
reduction in modulus as the higher curve
at the strain levels in question. The
net effect of all four parameters was
that the low core modulus values were
about one fourth the high core modulus
values .
A comparison of maximum dynamic horizon-
tal shear stresses for the two core modu-
lus conditions is shown in Figure 1A2 for
the bottom 135 metres (450 feet) of em-
bankment. A comparison for the top 90
metres (300 feet) is not shown because
the LUSH stresses are incorrect for
these upper elements (see next section) .
233
STRESSES BY LUSH FOR K
2 MAX
OF
130 INCORRECT IN UPPER 300 FEET
REANALYSIS EARTHQUAKE
COMPUTER PROGRAM LUSH
SHELL K2MAX = 130
POISSON'S RATIO = 0.3
NOTE
HIGHER CORE MODULUS ABOUT
4 X LOWER CORE MODULUS
Ar,y WITH LOWER CORE MODULUS
ATxy
Figure ]k2. Influence of Shear Modul
Dynamic Shear Stresses
Reducing the core modulus lowers the
core stresses, and raises the stresses
somewhat in the shells. The downstream
shell has the greatest increase — up to
40 percent. Most of the upstream shell
has very little stress increase. A
small zone adjacent to the base and the
core has a 20-percent increase. And a
narrow zone adjacent to the surface of
the upstream slope actually has a 20-
percent decrease.
Computer Programs LUSH and QUAD4
In order to resolve a question of unus-
ual shear stress time histories by LUSH,
and for general comparison, computed
stresses by LUSH and QUAD4 were compared.
Questionable shear stress time history
patterns were found mainly in the upper
90 metres (300 ft) of the maximum sec-
tion for the LUSH analysis with K„ of
130, for both the high and low core
shear modulus values. There were signi-
ficant shear stresses at time zero and
large-amplitude, long-period stress
fluctuations thereafter. A typical pat-
tern is shown in Figure 143. (These un-
usual patterns were not found in any
elements for the LUSH analysis using
K_ of 205).
zmax
The induced stresses should be zero at
time zero, and should be insignificant
for the first two seconds because the
input accelerations are insignificant
for the first two seconds. Furthermore,
WITH HIGHER CORE MODULUS
US of Core on Computed Maximum Horizontal
these questionable patterns bear no re-
semblance to other stress time histories
throughout the embankment, which start
at zero and have patterns consistent
with the input acceleration time history
Dynamic stresses were computed by QUAD4
for the same input used for LUSH:
Maximum section
Shell K^^^ = 130
Core, low shear modulus
Poisson's ratio =0.3
All time histories produced by QUAD4 had
patterns consistent with that of the in-
put earthquake motion. Shear stress pat-
terns by LUSH and QUAD4 are the same in
the lower part of the embankment, and
are distinctly different in the upper
90 metres, as illustrated by Figures
143 and 144. It is concluded that the
LUSH stresses in the upper 90 metres are
incorrect for the analyses using a
K^ of 130.
2max
The LUSH program was checked by analyz-
ing a sample problem. It gave the pres-
cribed results. Cause of the abnormal
behavior is still undetermined.
Figure 145 compares the maximum dynamic
horizontal shear stresses for LUSH and
QUAD4. In the lower part of the dam,
where the LUSH stresses are valid, the
two programs give about the same stress-
es except in a zone adjacent to the up-
stream slope, where LUSH stresses are
234
0. <
i
0>
>
* <::^
K
^
°Z /
/
<t u <
= 2
)
O UJ <f
_l ^
~J
:3
235
2 "-
a: ul
236
I
about 20 percent higher. In the upper
90 metres, particularly on the upstream
side, the LUSH stresses are as much as
60 percent greater than the QUADA
STRESSES BY LUSH FOR Kjmax OF
130 INCORRECT IN UPPER 300 FEET
ATxy BY LUSH
stresses. No conclusions may be drawn
in the upper elements other than that
f-e LUSH stresses are in error.
REANALYSIS EARTHQUAKE
LOWER CORE MODULUS
POISSON'S RATIO = 0.3
Figure ]k5. Comparison of Computed Maximum Horizontal Dynamic Shear Stresses
by Computer Programs LUSH and QUADA
It is recommended that in general use
of program LUSH, if stresses appear to
be out of line for any reason, the time
histories should be checked to see if
high stresses are occurring at time zero
and for the period of time before input
accelerations are significant.
Influence of Poisson's Ratio
A Poisson's ratio value of 0.3 was used
for all the dynamic analyses of the Oro-
ville embankment. On later reflection
it was realized that a value of 0.5 is
more appropriate for saturated soils
during undrained loading.
The influence of Poisson's ratio was
examined using the following input:
Model embankment (Figure 146)
Computer program LUSH
Shell K„ = 130
2max „ ,
Static stresses = Y H (soil
density x depth
of overburden)
Three Poisson's ratio conditions were
analyzed :
1. 0.3 for entire embankment
2. 0.45 for the entire embankment
3. 0.49 for saturated zone (upstream
half) and 0.3 for unsaturated
zone (downstream half)
Figure 147 shows the influence of Pois-
son's ratio on dynamic shear stresses.
The higher Poisson's ratios generally
cause about 10 percent higher dynamic
horizontal shear stresses in the central
portion of the embankment, but hardly
any difference at the base or crest.
Comparisons of horizontal and vertical
dynamic normal stresses are included in
Appendix E. Although the comparisons
were not made on the Oroville maximum
section directly, it is considered rea-
sonable to generalize them for applica-
tion to the Oroville section.
237
PHREATIC LINE
AREA BELOW
A PHREATIC LINE
54 ELEMENTS
63 NODES
MODEL EMBANKMENT
STUDIES PERFORMED =
3 ANALYSES CONDUCTED WITH INDENTICAL INPUT VARIABLES EXCEPT POISSON'S RATIO (V)
POISSON 'S RATIO CONDITIONS ANALYZED
I). POISSON'S RATIO = 0.30 FOR ENTIRE EMBANKMENT SECTION
2). POISSON'S RATIO = 0.45 FOR ENTIRE EMBANKMENT SECTION
3). POISSON'S RATIO = 0.49 FOR ELEMENTS BELOW PHREATIC LINE
POISSON'S RATIO = 0.30 FOR ELEMENTS ABOVE PHREATIC LINE
METHOD OF ANALYSIS = LUSH PROGRAM
HIGHEST FREQUENCY USED IN ANALYSIS = 8.0 HERTZ
EFFECTIVE STRAIN RATIO = 0.60
INPUT MOTION = REANALYSIS EARTHQUAKE
MAXIMUM ACCELERATION = 0.6g
AVERAGE MODULUS REDUCTION CURVE FOR SANDS
AVERAGE DAMPING CURVE FOR SANDS
STRESS CONDITIONS ASSUMED FOR STUDY
H = HEIGHT OF SOIL ABOVE ELEMENT CENTROID
y = DENSITY, 153 pcf FOR ELEMENTS ABOVE PHREATIC LINE
91 pcf FOR ELEMENTS BELOW PHREATIC LINE
= EFFECTIVE VERTICAL NORMAL STRESS I psf ) = / * H
= EFFECTIVE HORIZONTAL NORMAL STRESS ( psf ) = Kq^ct^'
-- COEFFICIENT OF EARTH PRESSURE AT REST = 0.60
K„
0- ■+20-,
o-^' = EFFECTIVE MEAN NORMAL STRESS! psf ) = — " — 3 ^—
K2MAX = SHEAR MODULUS PARAM ETER = 130 _i_
Gmax = MAXIMUM SHEAR MODULUS AT LOW STRAINS ( psf ) = 1000* Kg^AX * ^""'"'^^
Figure 1^6. Model Embankment for Determining Influence of Poisson's Ratio on
Dynamic Shear Stresses
238
A r xy iV =0.49/0.30)
ATxy (Z/=0.30)
REANALYSIS EARTHQUAKE
COMPUTER PROGRAM LUSH
K
2 MAX
= 130
Figure l'*?- Influence of Poisson's Ratio on Computed Dynamic
Shear Stresses
Influence of Embankment Section
Most dynamic analyses of dams are done
for the maximum section. However, other
sections could be more critical. To co-
ver the range of possibilities, two
other sections were analyzed using the
same input properties and conditions as
used for the maximum section:
Computer program QUAD4
Poisson's ratio =0.3
Shell K, = 130
Core G ^"'f^^ = 2200
CU shear strength envelope
Average modulus reduction curve
for clays
Finite-element meshes for the two sec-
tions were the upper rows of elements of
the maximum section mesh. Natural per-
iods and maximum crest accelerations for
the three sections are:
Elements
Height, metres/feet
First mode natural
period, sec.
Maximum horizontal crest
acceleration, g
Maximum vertical crest
acceleration, g
Maximum Section
564
225/750
1.98
0.64
0.38
Section 2
128
100/330
1.22
0.75
0.51
Section 3
66
64/210
.83
0.79
0.66
239
Figure 148 shows comparisons of the two
shorter sections to the maximum section
for maximum dynamic horizontal shear
stresses. With respect to the maximum
section, both short sections develop
less stress in the outer parts of the
shells, and about the same stress in
the center; on the average, most of the
upstream shell develops about the same
stresses.
SECTION 3 (64 METRES HIGH)
SECTION 2 (lOOMETRES HIGH)
REANALYSIS EARTHQUAKE
COMPUTER PROGRAM QUAD 4
SHELL K2MAX = 130
Figure 1^8. Comparison of Computed Maximum Horizontal Dynamic Shear
Stresses for Different Embankment Sections
240
Combined Influence of Variables
The submerged upstream gravel shell is
the area of concern for seismic stabil-
ity. The following table summarizes
the influence on stresses in that area
by the variables studied:
Variable (Figure)
Shell K„ (35)
2max
Core Shear
Modulus
(36)
Range
205 vs. 130
Lower vs Higher
Influence on Dynamic
Horizontal Shear Stresses
in Upstream Shell
(Percent Difference)
+20 to +70*
0 to -20*
Computer (39)
Program
Poisson's (41)
Ratio
Embankment (42)
Height
LUSH vs. QUAD4
0.45 vs. 0.3
100 metre vs.
230 metre
0 to +20*
0 to +5
0 to ilO
*Not defined in upper 90 metres because LUSH stresses with K„ = 130
^ . \,, . 2max
are incorrect in this area.
For the dynamic shear stresses in the up-
stream shell, the influence of Core
Shear Modulus, Computer Program, Pois-
son's ratio, and Embankment Height are
relatively minor over the range of val-
ues studied. However, for the combina-
tion of Program LUSH and higher shear
modulus in the core, the 20 percent dif-
ferences are cumulative in a shallow
zone along the upstream slope. This is
the combination used to calculate stress-
es for evaluation of embankment perform-
ance and will give the highest stresses
in this zone.
The major influence is shear modulus of
the shell. Increasing shell K„ by a
£ ^ c t n \. 2max -^
factor of 1.6 causes shear stresses to
increase by 1.2 to 1.7. The choice of
^2max ^^^^^^ ^^^ range 130-205 will be
a major determinant of computed embank-
ment performance. The conservative ap-
proach would be to use a value around
200 - near the upper end of the range.
Three-Dimensional Effect
Jlomparisons of stresses by two-
dimensional (plane strain) and three-
dimensional analyses are shown in Figure
149 (after Makdisi, 1976) for a dam with:
H = 30 metres (100 ft)
L/H = 3
Slopes =2:1
V = 150 metres per second (500 feet
per second)
Damping = 10%
Earthquake = Taft (first 15 seconds)
a = 0.2g
max °
For the maximum section, the three-
dimensional analysis gives stresses at
the crest, base, and slope areas that
are 50 percent to 100 percent lower than
those for the plane strain analysis. In
the central portion, stresses are the
same for 2D and 3D analyses.
241
L/H =3
00 %
MID-SECTION
1
-50^'^^^.
"^f\
o
If)
- 90%^.
z-?^^^
'
1
^—80'
"^^^^"-^
AFTER MAKDISI (1976)
QUARTER SECTION
Figure 1^49. Comparison of Maximum Horizontal Shear Stresses Determined
from 3D and Plane Strain Analyses Using Base Motions from Taft Record
For the quarter section, stresses by 2D
and 3D analyses differ by less than 20
percent for most locations, but near the
crest the 3D stresses are twice as high
as 2D stresses.
242
For Oroville Dam with L/H = 7, smaller
differences would be expected between
2D stresses and 3D stresses.
One way to estimate the 3D stresses for
the Oroville maximum section is to use
the embankment response model defined
in Section 5. The implied assumption
here is that the same pseudo K„ value
(350) which accounted for abutment re-
straint effects in the August 1, 1975
earthquake will also correctly account
for abutment restraint effects in the
Reanalysis Earthquake. Then the model
will give the correct period and accele-
ration response, and the correct comput-
ed linear elastic shear strains in the
maximum section of the actual (3D)
embankment.
The effect of abutment restraint is to
reduce the strains of the maximum sec-
tion by developing shear stresses on its
sides. Thus all the inertia forces ao
not have to be borne by shear stresses
on the tops and bottoms of elements. It
is these top and bottom stresses that
are usually of concern in relation to
embankment behavior. These element top
and bottom shear stresses can be calcul-
ated by multiplying the shear modulus
of the material by the 3D shear strains
obtained from the embankment response
model .
The embankment response (3D) was calcul-
ated for the following conditions:
Computer Program LUSH
Maximum Frequency Used 10 Hertz
Maximum Section
Shell - Pseudo K„ = 350
- Average Modulus Reduction Curve
for Sands
- Average Damping Curve for Sands
Core - G^g^/S = 1750
- Shear Strength Envelope UU
- Higher Modulus Reduction Curve
- Average Damping Curve for Clays
Poisson's Ratio 0.3
Appendix E includes 2D shear stresses for
pseudo K2niax ~ 350; Appendix F explains
the method used to calculate 3D stresses.
Figure 150 shows the ratio of 2D to 3D
stresses in the upstream shell computed
for shell K^ ^^ of 205. In the lower
interior part^of the upstream shell, 2D
and 3D stresses are the same; in the
central part and upstream of the coffer-
dam core, 2D stresses are 25 percent
higher; in the upper part, 2D stresses
are over 50 percent higher. These re-
sults are similar to Makdisi's in the
upper part of the dam, but the differ-
ences between 2D and 3D stresses is much
less than those (Makdisi's) along the
slope and base.
OROVILLE DAM - MAXIMUM SECTION
REANALYSIS EARTHQUAKE - MAXIMUM ACCELERATION
LUSH DYNAMIC RESPONSE ANALYSIS
PSEUDO K2MAX = 350
PSEUDO Gmax ' Su = 1750
SHELL KjMAX
CORE Gmax > ^n = M20
0.6 g
MAXIMUM AT , FOR PLANE STRAIN CONDITIONS MAXIMUM Ar,„ ( K,
MAXIMUM Ar,„ FOR PSEUDO -3D CONDITIONS
205) 350
MAXIMUM Ar,y (K2MAX=350)
Figure 150. Estimated Three-Dimens ional Effect on Computed Maximum Hori-zontal
Dynamic Shear Stresses
243
8. CYCLIC SHEAR STRENGTH
Cyclic Strength Test Program
Cyclic strength testing was carried out
only for the saturated upstream gravel
shell and transition. The downstream
shell is not saturated and would be much
stronger — with cyclic strength essen-
tially equal to the static effective
strength. The two clayey gravel cores
occupy a relatively small proportion of
the embankment. Also, studies have
shown that compacted clayey embankments
perform well during earthquakes (Seed,
Makdisi, & DeAlba, 1978).
The cyclic triaxial testing was carried
out under the direction of Professor
H. B. Seed at the University of Califor-
nia, Richmond Field Station. The prograi
consisted of about 90 cyclic triaxial
tests on 30-cm (12-inch) diameter sample:
to measure the cyclic strength of the
gravel; and about 12 cyclic triaxial
tests on 7.1-cm (2.8-inch) diameter sam-
ples to determine the effects of aging.
Tests of the larger samples included the
following consolidation conditions to
represent a wide range of locations with-
in the upstream shell:
Minor Principal
Consolidation Stress
196 kilopascals (4100 psf)
784 kilopascals (16,400 psf)
1370 kilopascals (28,700 psf)
2550 kilopascals (53,300 psf)
Consolidation
Stress Ratio
K = g' Ic/ g' 3c
1, 1.5 & 2
1
1, 1.5 & 2
1. 1.5 & 2
Sample Gradations and Density
Modeling Embankment Shell Gradation
Zone 3 materials are sands, gravels,
and cobbles up to 15 cm (6 in.) size.
Figure 151 shows the average gradation.
Even for gradations coarser than the
average, maximum particle size rarely
exceeds 22.5 cm (9 in.) with only a
small percent of material larger than
15 cm (6 in.).
Testing of smaller size particles to
represent full-scale material has been
done for many years. Lowe (1964) was
the first to use a model gradation
parallel to the field gradation. This
modeling method has since been used by
others, notably Marachi et al (1969),
Becker et al (1972), and Wong (1973).
Marachi and Becker did static shear
tests on full-size field gradations of
Oroville Zone 3 material as well as on
the modeled gradation. When compared
at equal relative densities, the fric-
tion angle for the two parallel grad-
ations was the same (maximum difference
was one degree) .
The same modeled gradation has been
used in this study for the cyclic tri-
axial tests on gravels. Additionally,
a second modeled gradation was used for
cyclic triaxial tests of smaller sam-
ples (Figure 151). The ratio of sample
diameter to maximum particle size is
six.
Relationship of Test Sample Density to
Field Density
The objective was to prepare test sam-
ples at the same percent compaction as
achieved for the Zone 3 shell material
compacted into the embankment. Figure
152 shows the statistical distribution
of percent compaction in the shell.
I
244
U.S. STANDARD SIEVE SIZES
0.5 1.0 5.0 10.0
GRAIN SIZE IN MILLIMETRES
100.0
Figure 151. Field and Modeled Oroville Gravel Gradations
Average = 99%
Standard Deviation = 4%
Significant Range = 90% - 110%
Figure 153 shows that most of the gra-
vel shell contained between 5 percent
and 20 percent minus No. 4, with an
average of 14 percent; and that for
this average gradation, the average
compaction achieved was 100 percent at
a dry density of 2 387 kilograms per
cubic metre (149 pcf).
Maximum density tests were carried out
on samples of minus 5-cm (2- in.) mater-
ial (modeled gradation) to be used for
the cyclic triaxial tests. The same
equipment and procedures were used for
these tests as for the control tests
run during construction. Test proce-
dures are described in the Oroville Dam
Embankment Materials Report. In sum-
mary, the test consists of vibrating a
500 kilogram (110-lb.) saturated sam-
ple in a 67. 5-cm (27-in.) diameter
mold for five minutes with a 13.8-
kilopascal (2-psi) surcharge. Vibra-
tion is with a foundry type air-driven
vibrator at a frequency not less than
7,000 VPM. During vibration the mold
is lifted off the floor.
245
100
^ 75
IxJ '^
50
25
mm
I II I II I M I M I
X = 99.0
a = 4.2
N = 841
84 86
92 94 96 98 100 102 104
PERCENT COMPACTION
06 !08 110
OROVILLE DAM
Figure 152. Final Statistical Analysis - Zone 3, Percent Compaction
246
PER CENT PASSING NO. 4 SIEVE
10 20 30 40
160
150
140 -
130
50^
■ AVERAGE OF MAXIMUM
DENSITY TESTS
/'AVERAGE OF FIELD
/ DENSITY TESTS
_1
Q
u.
a:
<
U-
>
o
10
o
u
m
5
z>
z>
u
_J
o
o
20
10 20 30
PER CENT PASSING NO.
Figure' 153. Field Control Tests - Zone 3
Figure 154 shows the results of these
tests, along with construction control
test results of samples with 14 percent
minus No. 4. For the six tests on mod-
eled gradation samples, maximum density
appears to be a function of vibration
frequency. However, the construction
control tests show a general scatter
with no apparent correlation.
This difference is understandable. For
the tests on modeled gradation material,
the gradation and specific gravity were
exactly the same for all tests; and the
tests extended over a period of two
weeks during which vibrator character-
istics would not be expected to change
drastically. By contrast, the construc-
tion control tests were run over a
period of several years on materials
with varying gradations and specific
gravity.
The frequency of vibration generally
varied from 8,000 to 12,000 VPM, aver-
aging 10,000 VPM during construction
control testing. Therefore, it seems
appropriate to use a frequency of
10,000 VPM for maximum density testing
of the modeled gradation material. An
average density of 2 390 kilograms per
cubic metre (149 pcf) was used for set-
ting up cyclic triaxial test samples.
The range was 2 360 to 2 410 kilograms
per cubic metre (147 to 151 pcf) and
the standard deviation was 18 kilograms
per cubic metre (1.1 pcf). Both maxi-
mum density at about 10,000 VPM and
247
160
150
140
If)
■2.
LU 130
X I 50
<
RANGE OF FREQUENCIES USED
IN CONSTRUCTION CONTROL TESTING
8000 TO 12000 RPM
130
> MAXIMUM DENSITY AT
9700 RPM , 155 pcf
AVERAGE MAXIMUM
DENSITY 150 pcf
MODELED GRADATION
2INCH MAXIMUM, 30%-*4
TESTED AT BRYTE LAB.
AVERAGE TEST -...
FREQUENCY 9700 RPM
^
I
ONE TEST AT BRYTE LAB
•t
AVERAGE MAXIMUM
DENSITY 148 pcf
APPROX AVERAGE GRADATION
6" MAXIMUM, l4%-*4 TESTED
AT OROVILLE LAB DURING CONST.
J \ \ I
7000
8000
9000 10000 1 1000
FREQUENCY (RPM)
12000
13000
27 INCH MOLD
AIR VIBRATOR
1100 POUND SAMPLE
2 psi SURCHARGE
5 MINUTE VIBRATION
Figure 15^. Maximum Density Tests - Zone 3
average maximum density for 7,000 to
10,000 VPM are considered in comparing
sample compaction with field compaction
in the following table :
248
Compaction
Conditions
Average Maximum Density
for All Frequencies
Average Placed Density
Average Percent Compaction
All Zone 3
Material
99%
Material With
Average Gradation
in Zone 3
Embankment
148 pcf
149 pcf
101%
Cyclic
Triaxial
Samples
150 pcf
149 pcf
99%
Average Maximum Density
for Frequencies From
9.500 to 10.000 VPM
Average Placed Density
Average Percent Compaction
150 pcf
149 pcf
99%
155 pcf
149 pcf
96%
Range of Percent
Compaction
91% - 107%
(+2 standard
deviations)
95% - 100%
The average percent compaction of the
cyclic triaxial test samples is slight-
ly (2 percent to 3 percent) less than
the average percent compaction of Zone
3 material with average gradation; and
also slightly less (0 to 3 percent)
than the average percent compaction of
all Zone 3 material.
Summary of Test Procedures
30 cm Diameter Samples
The sample was manufactured in 10 lay-
ers in a membrane-lined mold on the tri-
axial test base. Material for each
layer was weighed, mixed, placed in the
mold, and vibrated for four minutes by
a vibrating weight placed on top of the
layer. The top cap was placed on the
sample, a vacuum applied, the mold re-
moved, and a second membrane installed.
The chamber was assembled on the base,
filled with water, and pressurized.
The sample was soaked by flowing water
upward through it, and then backpres-
sured until pore pressure parameter B
was 0.9 or higher. Back pressure for
most tests was 392 kilopascals (8,200
psf). After consolidation was com-
plete, cyclic loading was applied at a
frequency of one cycle per minute, be-
ginning with the compression half.
Loads were set to be sinusoidal and
syimnetrical about the static axial
deviator stress. The slow frequency
was necessary for the hydraulic load-
ing system to maintain scheduled loads
as the sample underwent large displace-
ments. Continuous records were made
of Ipad, displacement and pore pressure.
7.1 cm Samples
Procedures were basically the same as
for the larger samples. Exceptions
were:
1. Material was not mixed individually
for each layer.
2 . Sample was made in five layers ra-
ther than ten .
3. Half of the samples were allowed to
consolidate for two months before
testing.
249
4. Loading frequency was one cycle per
second.
Results of Cyclic Triaxial Tests
The testing report (Appendix L) , which
is now being prepared, will be provided
on request when it becomes available.
Copies of the test records and associ-
ated data, plots of cyclic stress vs.
number of cycles for specified strains,
and cyclic strength envelopes, all for
tests of 30-cm (12-in.) samples, have
been provided to DWR. Summaries of the
test records are included in Appendix G.
The cyclic strength enveopes are dis-
cussed in the next section.
Detailed results of the aging tests on
7.1-cm C2.8-in.) samples have not been
provided yet. A verbal report was made
that aging did not produce any strength
gain.
Most of the tests were successful, but
some records show deficiencies. Typ-
ical test records for successful tests
are shown in Figures 155 and 156. The
deficiencies were mainly found on tests
with isotropic consolidation (K = 1)
and include the following:
1. Loading was more than 10 percent
asjTmnetric and drifted or jumped dur-
ing the test. In addition, the load-
ing amplitudes often attenuated quite
severely with succeeding cycles.
About half of the samples consoli-
dated isotropically at 785 kilo-
pascals (16,400 pounds per square
foot) suffered from severe attenu-
ation. An example of such load
attenuation is shown in Figure 157.
2. Load jumps and unusual pore pressure
jumps rendered about the first 20
cyclic tests questionable. It was
unfortunate that most of the
isotropically-consolidated tests at
an initial confining pressure of 196
kilopascals (4,100 psf) were in this
group. Exan^sles of such tests are
shown in Appendix G.
3. Many samples which developed signi-
ficant strain produced symptoms of
necking.
4. Many samples which developed only
a small amount of strain were tested
for only a relatively few number of
cycles. For example, except for two
tests which experienced severe load
attenuation, all of the samples con-
solidated isotropically to 784 kilo-
pascals (16,400 psf) were stressed
only to 12 cycles or less.
5. After the testing program was com-
pleted, the load calibration was
found to be different from the des-
ignated value. The actual applied
loads were approximately 15 percent
higher than those recorded. The
correction not only changes the val-
ues of the cyclic stresses but also
alters the values of the anisotropic
consolidation stress ratios, because
the hydraulic actuator was used to
increase the major principal consol-
idation stress to a higher value
than the minor principal consolida-
tion stress. There were some check
tests performed in an attempt to as-
certain when the calibration actual-
ly deviated from its designated
value. On the basis of these tests,
this point was found to be about
halfway through the testing program.
However, the 15 percent difference
would be virtually impossible to
find by check tests, because the
variations of cyclic test results
are at least that large. It is also
quite reasonable to assume that the
calibration error was present through
out the testing program.
Several corrections must be made to the
cyclic triaxial stresses on the rest
records :
1. The C correction is made because
the triaxial test does not duplicate
the stresses present in an actual
soil element. A C value of 1.0
X"
is usually us'ed for anisotropically-
consolidated samples; a value of
250
about 0.6 is used for isotropically-
consolidated samples.
2. Axial stresses should be multiplied
by 1.15 to correct for the load cal-
ibration error. For the anisotrop-
ically consolidated samples this
will also give slightly higher con-
solidation stress ratios. K values
c
of 1. 5 and 2 should be changed to
1.57 and 2.15 respectively.
3. Membrane Strength Correction: This
correction is used to account for
the fact that the membranes surround-
ing the sample carry some of the ap-
plied axial load. The correction is
a function of the induced strain and
is shown in Appendix L (available
later in 1979) • This correction be-
comes significant only at the lowest
effective consolidation stress used
in this study.
4. Membrane Compliance Correction -
During consolidation, the membrane
penetrates into spaces between part-
icles around the surface of the sam-
ple. During cyclic loading, pore
pressure increases are a controlling
factor in sample behavior. The sys-
tem is intended to be undrained,
keeping the pore volume constant.
However, if the membrane penetration
decreases slightly, the pore volume
expands slightly and the pore pres-
sure increase is less than if the
voltmie was kept constant. Verbal
reports are that cyclic stresses
should be multiplied by 0.9 to ac-
count for membrane compliance.
Investigation of Sample Behavior of
Dense Sands in Static and Cyclic
Triaxial Tests
Objective
Many limitations of the cyclic triaxial
test have been pointed out by Seed and
Peacock (1970) and by Seed (1976) and
include :
1. The cyclic triaxial test does not
reproduce the correct initial stress
conditions within the ground.
2. There is a 90° rotation of the direc-
tion of the major principal stress
during the extension and compression
halves of the loading cycle.
3. The intermediate principal stress
does not have the same relative val-
ue during the two halves of the load-
ing cycle .
4. Unless special precautions are
taken, friction may develop between
the san5>le and the end caps, which
will cause stress concentrations.
5. During the extension half of the
stress cycle, necking may develop
and invalidate the test data beyond
this point in the test.
These limitations are legitimate, but
the test is used despite them, because
triaxial test results have been success-
fully related to other cyclic shear
tests such as the cyclic simple shear
by an appropriate correction factor.
However, consideration of these limit-
ations played an important role in the
interpretation of the cyclic triaxial
tests carried out for the modeled Oro-
ville gravel samples. The cyclic test
results for the isotropically consoli-
dated samples produced many questions
concerning the development of sample
strain. These samples produced strain
almost totally in the extension direc-
tion. There was debate over whether
some samples developed only a limited
amount of strain during testing. It
seemed that many samples required cyc-
lic "tension" stresses
(o dp/2a '3c">0. 5) to produce signifi-
cant strain levels. Other samples ex-
hibited so much extension strain that
necking was suspected. A single cause
for this behavior was difficult to iso-
late due in part to the severe load
attenuation during many of these tests.
251
It was not clear whether the previously
mentioned test limitations were the
cause of the described behavior, or whe-
ther the test results were valid (as
valid as triaxial tests that don't pro-
duce this observed strain behavior) .
Of particular concern was resolving
whether these test results could be
used to evaluate the performance of
the embankment during earthquake
shaking.
Since available information on the be-
havior of very dense samples is limit-
ed, it was decided to conduct a labora-
tory investigation to examine more
closely the behavior of dense samples
and to document the results photograph-
ically. The specific objective was to
answer these three questions:
Is the development of primarily ex-
tension strain a valid result for
isotropically consolidated dense
samples, or is it a product of an
erroneous test condition such as
sample necking?
Did the isotropically consolidated
cyclic tests on the modeled Oroville
gravel develop necking problems?
What happens to an isotropically
consolidated sample when the cyclic
stress ratio (a , /2a'_ ) exceeds
0.5 (tension) and does this consti-
tute a valid test condition?
ts^o
-8200'-
TEST NO. 72
Vd = 149 5pcf
Kj =1.0
CTj'c = 16400 pcf
Figure 155. Cyclic Triaxial Test Records for Modeled Oroville Gravel
252
TEST NO 45
y^ = 149 2 pcf
Kj = 2.0
CTj'c = 28700 psf
TEST NO 56
Y^ = 149 5 pcf
Kj =15
o-3'e= 53300 psf
Figure 156. Cyclic Triaxial Test Records for Modeled Oroville Gravel
253
55^
tlWtWtWi Ittlltlllllllt
\l
?ii
^
^'fy
^
r r ^ ^ f\
' \ ,0 ,5 i ! 20
f"
11
1
1
n '^
1
J
1
1/
^
J
b
J
1
lil
95
100
Figure 157. Cyclic Triaxial Tes
Program and Procedures
Approximately 60 static and cyclic tri-
axial tests were carried out on dense
samples with particular attention to
observing sample behavior and relating
it to strain and pore pressure charac-
teristics. The tests were conducted
at the Department of Water Resources'
Laboratory at Bryte and at the Depart-
ment of Transportation Laboratory in
Sacramento. The two materials tested
were Monterey "0" sand and the minus
1.27-cm (1/2-inch) portion of the mod-
eled Oroville gravel, designated Oro-
ville sand. The gradations of these
two test materials are shown in Figure
158. Films, slides, and photographs
were taken during the tests to document
sample behavior and aid in the inter-
pretation of the test measurements.
Monterey "0" sand was used to investi-
gate the behavior of dense, cohesion-
less samples that were constructed as
uniformly as possible and tested under
ideal conditions. The behavior of
these uniform samples could then be
TEST MO 76
Tj " 149 7 pet
Ke • 1.0
0-3'^' 16400 pif
t Records for Modeled Oroville Gravel
compared to the behavior of samples
that simulated the sample characteris-
tics of the modeled Oroville gravel.
The Monterey "0" sand was chosen be-
cause it has a uniform gradation and
has been used extensively in previous
investigations. These samples were
prepared by pluvial compaction through
air in an attempt at producing the most
uniforto sample possible. In addition,
the samples were capped with "friction-
less" Incite platens lubricated with
silicon grease and covered with a cir-
cular piece of rubber membrane.
The Oroville sand material was used to
represent the sample characteristics of
the modeled gravel samples. Both types
of samples had gradation curves parallel
to the average field gradation and had
the same ratio of sample diameter to
maximum grain size. Both types of sam-
ples would also be constructed using
the same preparation technique (high-
frequency vibration in layers). No
special precautions were taken to mini-
mize the friction at the end platens.
254
U.S. STANDARD SIEVE SIZES
100
90
^200 '^lOO *50 *30 *I6 *8 **
4 3/8" 3/4" I 1/2"
6 12
I 70
LlI
60
50
40
O
tr
^ 30
Q.
20
10
1
1
/ '
1 1/
f
1
1
\
1 1
MONTEREY
/
1
U
SAND
S
t\
1
1
1
\
a
^^~~-~ (
)ROVI
_LE S/
\NDS
\
>
/
L
/
/
^
f
1
y
1
1
1
1
1
1
0-5
1.0 5.0 10.0
GRAIN SIZE IN MILLIMETRES
50.0 100.0
Figure 158. Monterey "0" Sand and Oroville Sand Gradations
255
All of the samples constructed were
12.7 centimetres (5 inches) high and
6.4 centimetres (2.5 inches) in dia-
meter. Monterey "0" sand samples were
confined by a 0.3-millimetre (0.012-
inch) rubber membrane and the Oroville
sand samples by either a 0.3- or 0.6-
millimetre (0.012- or 0.025-inch) rub-
ber membrane. Most of the Monterey "0"
sand samples had dry densities ranging
from 1 698 to 1 714 kilograms per cubic
metre (106 to 107 pounds per cubic
foot). A few additional static test
samples, however, were constructed with
dry densities of about 1 569 to 1 586
kilograms per cubic metre (98 to 99
pounds per cubic foot).
The Oroville sand samples were prepared
in five 2.5-centimetre (1-inch) layers
and had dry densities of approximately
2 275 kilograms per cubic metre (142
pounds per cubic foot). The relative
density of the very dense Monterey "0"
sand samples was estimated to be 95 to
100 percent. The relative density of
the Oroville gravel samples was esti-
mated to be about 85 to 90 percent.
Saturation details are similar to those
used by Mulilis et al (1975). Carbon
dioxide gas is first passed through the
sample to replace the air within the
voids and cell lines. Carbon dioxide
is used because its solubility in water
is much greater than that of air. After
the carbon dioxide stage, de-aired wa-
ter is slowly introduced into the sam-
ple from the bottom. The water moves
into the sample at a very slow rate,
filling most of the voids in the sam-
ple. After passing water through the
sample, back pressure is applied to
dissolve any remaining gas bubbles.
The degree of saturation is checked by
measuring the pore pressure parameter
B. Almost all samples tested had B
values of 0.90 or greater and back-
pressure values equal to 393 kilopas-
cals (8,200 pounds per square foot).
All samples tested were consolidated
isotropically to an effective consoli-
dation pressure of 196 kilopascals
(4,100 psf).
Static Tests on Monterey "0" Sand
Static tests were conducted only for
the Monterey "0" sand samples. Consol-
idated undrained tests were carried out
for medium and very dense samples in
both the compression and extension di-
rections, with a strain rate of 0.03
percent per minute.
Typical stress and pore pressure devel-
opment with strain are shown on Figures
159 and 160. The following observa-
tions may be made :
1. For all of the tests conducted, the
pore water pressure increases at low
strains. After a certain strain val-
ue is reached, the pore pressure be-
gins to decrease. This drop in pore
pressure continues until the sample
fails. The pore pressure develop-
ment with strain is nearly identical
in both the extension and compression
directions.
2. The maximum stress and the slope of
the stress-strain curves are much
greater for the compression tests
than for the extension tests, thus
indicating the relative weakness of
the extension direction.
3. At a given axial stress, the lower
density samples strain farther than
do the higher density samples. This
is true for both the extension and
compression directions.
4. The difference in the slopes of the
stress-strain curves in the extension
and compression directions is more
pronounced in the samples of higher
density.
Figure 161 summarizes eight stress-
strain curves for the static tests con-
ducted on the very dense samples of the
Monterey "0" sand. The compression modu-
lus is about five times the extension
modulus.
256
50000
40000
-| r
AXIAL STRAIN (%)
4 5 6 7 8
-| T
▲
— r
▲
i-- 106.8 pcf
d
IS)
UJ
^ 30000
i
en
O
A
- 20000
-
UJ
O
▲
▲
10000
'a •
r
Y'- 99.4 pcf
d
J L
J L
+ 2000
UJ
QL
■n
UJ
a:
Q.
UJ
o
Q.
STATIC TRIAXIAL COMPRESSION
Kc = 1.0
a3c' = 4100 psf
Ub = 8200 psf
-4000
-8000
d'^-- 99.4 pcf
-^ ^j = 106.8 pcf
J L
3 4 5 6 7
AXIAL STRAIN (%)
10 II
Figure 159- Typica
Monterey "0" Sand
1 Static Triaxial Compression Test Results for
AXIAL STRAIN (%)
10000
1
2
3 4
5 6 7 8
9
10 II
1
1
1 1
A ^
1 - . ,
1
1
in
a.
8000
A
/j = 106.6 pcf
b
CO
in
LiJ
tr
1—
CO
(E
6 000
-
A
A
•
•
. • • •
•
•
•
-
1-
<
>
IT
ff , " JO.O^ [Jul
4 000
-
f
-
Q
2000
4
A
1
1
9
1 1
1 1 1 1
1
1
-
STATIC TRIAXIAL EXTENSION
Kc = 1.0
(/)
+ 2000
-
(T2,c ^ 4100 psf
Ub = 8200 psf
-
a
0
4
P^
!^
3
▲
^
^
3
CO
CO
UJ
IE
0.
UJ
-4000
-
A
A
••
1 1
/j =98.84 pcf
•• • • •
106.6 pcf
•
•
-
q:
o
-8000
_
1
1
A A A A
■ III
1
1 1
-
3 4 5 6 7 8
AXIAL STRAIN (7o)
10 II
Figure 160. Typical Static Triaxial Extension Test Results for
Monterey "0" Sand
258
16000
-
1
•
♦
1
1 1
1
14000
-
-
♦
12000
-
♦
-
10000
-
i
•
-
8000
O
♦
•
V
6000
♦
•
V
4000
-o
DA
-
2000
♦
3
DA
•
V
•
V
1
V
1
1 1
1
2 3 4
AXIAL STRAIN (%)
Kc=l
.0,
Cr3C=
4,100 psf
STATIC COMPRESSION TESTS
STATIC EXTENSION TESTS
# TEST NO. A , S^d = 106.5 pcf
V TEST NO.B, ^d = 106.9 pcf
■ TEST NO. F , if d = 106.8 pcf
• TEST NO.E, Vd = 106.6 pcf
♦ TEST NO. N , V d = 106.6 pcf
n TEST NO.CD.i^d = 107.1 pcf
O TEST NO. CB, tfj = 106.4 pcf
A TEST NO.CE, Vd = 107.1 pcf
Figure I6l. Summary of Static Triaxial Test Results for Dense
Monterey"0" Sand.
259
Cyclic Tests on Monterey "0" Sand
Cyclic stress ratios (a, /2a\ ) vary-
ing from 0.3 to 2.2 were used m the
testing of very dense Monterey "0" sand
samples. Results of these tests showed
that the axial strain developed almost
totally in the extension direction.
This was true despite the fact that the
samples were carefully prepared and com-
posed of uniformly graded sand. This
behavior is illustrated in Figure 162,
which presents the cyclic strain enve-
lopes for several tests. Observations,
photographs and movies made during test-
ing show that the asymetric strain is
not caused by sample necking. Most sam-
ples retained a uniform cylindrical
shape until the final two or three cyc-
les, when distinct failure occurred.
The strain levels (1/2 peak-to-peak)
developed in ten cycles for the tests
shown in Figure 162 plotted against cyc-
lic deviator stress ( o dp) in Figure
163. Also shown are the average static
stress-strain curves for both the com-
pression and extension directions. The
cyclic test results plot along the sta-
tic extension stress-strain curve.
After the first few cycles, the rate of
strain increase is quite gradual for all
of the cyclic triaxial tests depicted in
Figure 162. This was true despite the
fact that the peak pore water pressure
values are at, or close to, the initial
confining pressure and that the cyclic
stress ratios were extremely high. The
highest strain level reached was only
+5 percent. For each test, despite the
70 80 90 100
NUMBER OF CYCLES
Figure 162. Cyclic Triaxial Strain Envelopes for Monterey "0" Sand
260
T 1 T 1
•
-
^ — AVERAGE OF STATIC
COMPRESSION TESTS
-
\. + AXIAL STRAIN
/^ FOR 10 CYCLES OF
- /
/ CYCLIC TEST
-
/
.
>
(^^«
J
^~~^AVERAGE OF STATIC
-
;i
EXTENSION TESTS
/
f
•
Kj = 10
CTj^' = 4100 psf
1
AXIAL STRAIN (%)
Figure 163. Static and Cyclic
Triaxial Test Results for Dense
Monterey "0" Sand
value of the stress level, the sample
reached a point where the rate of strain
increase was so low that it would have
required tens or hundreds more cycles
to develop an additional one percent of
axial strain. This behavior has been
described as limiting strain by Mulilis
et al (1975) and DeAlba et al (1975),
who also tested samples of Monterey "0"
sand. Mulilis performed his tests us-
ing cyclic triaxial equipment, whereas
DeAlba used large-scale simple shear
(shaking table) apparatus. Both stud-
ies found a general increase in the
limiting strain as the relative density
decreased.
In Figure 164, the cyclic test results
are presented as the number of stress
cycles required to produce a specified
amount of strain for different stress
levels. Extremely high cyclic stress
ratios (a 11 o\ ) were required to
cause significant strains in relatively
low numbers of cycles. These cyclic
stress ratios ranged as high as 2.2 for
these tests. However, tests having cyc-
lic stress ratios greater than 0.5 have
often been classified as having erron-
eous tensile stresses. Many refer-
ences, including the U. S. Bureau of
Reclamation (1976) and Seed et al
(1975), state that exceeding the 0.5
cyclic stress ratio boundary can cause
the sample cap to lift off, which may
result in the sample failing premature-
ly by necking near the top.
The tests carried out for the dense
samples of Monterey "0" sand showed
that large cyclic stress ratios (great-
er than 0.5) do not necessarily produce
cap lift off and necking at the top of
the sample. The large stress ratios
produced uniform strains throughout the
length of the sample, the same as for
samples tested at much lower stresses.
Figure 165 shows portions of the cyclic
tesj: records for samples tested with
cyclic stress ratios of 0.27 and 1.0.
The only difference that may be ob-
served in the strain development in the
two tests is that the larger stress
ratio produces a higher level of strain
in the first few cycles. This charac-
teristic was generally true for all the
cyclic tests conducted on the Monterey
"0" sand. The larger the' applied
stress, the higher the strain level be-
came in the first few cycles.
It should be noted that all of t.he cyc-
lic tests were continued until the
samples eventually necked. The necking
developed despite the fact that these
samples were carefully prepared and
tested. However, this was not caused
by the cap lifting off and causing a
neck at the top of the sample. Necking
developed at different locations for
different samples anywhere from the bot-
tom of the sample to the top. In addi-
tion, most Monterey "0" sand samples
only indented slightly before the devel-
opment of a shear plane. A typical
shear plane is shown in Figure 166.
After the development of a shear plane,
the samples quickly necked completely.
261
18000
(
)
1
1
1 1 1
1 1 1 1
\
1 1 1 1 1 1
\ °
III 1
-
—
16000
_
\ %
-
\ Vl*
Q.
\ ^<
\ ^>k
14000^
_
V, 'Z,
_
+1
(
\
\^\
12000
\
\
_
LiJ
\
a:
X
\-
N
\
CD
10000
-
\
-
(T
\
>.
O
>y^
<
8000
-
^
sO O
-
>
UJ
Q
O^
6000
—
—
O
_l
o
^^\^o
^^/>
o^^^^
>-
o
4000
-
Kc =
1.0
o
^^^o
-
^,-
106 -
- 107
pcf
2000
-
<^3c
' = 4100 p;
f
o
-
1
1
1 1 1
1 1 1 1
1 1 1 1 1 1
III 1
100
13 10 30
NUMBER OF CYCLES
Figure ]Sk. Cyclic Triaxial Test Results for Monterey "0" Sand
300
The development of this necking behavior
is illustrated in Figure 167.
Cyclic Tests on Oroville Sand. Ten
cyclic triaxial tests were carried out
for the Oroville sand samples. The
cyclic stress ratios ranged from 0.3
to 1.0 and the samples were cycled un-
til they necked.
These samples also developed predominant
extension strain although the magnitudes
were slightly higher than for the Mont-
erey "0" sand samples. In addition, ob-
servations and photographs reveal that
the necking was different for these
samples than for the Monterey "0" sand
samples. Instead of developing a shear
plane in the final stage of necking, the
Oroville sand samples developed strain
concentrations and indentation in the
middle portions of the samples. These
necks seemed to always be concentrated
in one of the middle layers. In gener-
al, these samples did not remain as uni-
form as the Monterey "0" sand samples
prior to the final stages of necking.
Figures 168 and 169 illustrate this
behavior.
262
Hi UJ
^ en
if)
^ III
s?
CYCLES
tr
4100
lU UJ
H cc
<=>"S
0
? V) CL
CO 1
U UJ 3
-4100
cr (r
o Q-
-8200
TEST NO 12
Kc = 1.0
D'jc=4IOO psf
Yd = 106.6 pcf
Odp/2CTje=0.27
— (_ to O. 1|^ '
-" < Lij I n k
o _ q: Q. 0 ,
"Jii'^^ looooJfe
TEST NO. 15
K = 1.0
Csc^ 4100 psf
ti- 106.2 pcf
Odp^2a,e=I.O
Figure I65. Cyclic Triaxial Test Records for Monterey "0" Sand
19—78786
263
Figure 166. Shear Plane Development during Final Stage of Necking for
Monterey "0" Sand
264
a: -4 000-
Ttnrf
185 190
EXTENSION PORE CHARACTERISTIC
PRESSURE PEAKS PORE PRESSURE
INCREASE IN DROP PEAK
CHARACTERISTIC ,
LOAD PEAK-
STRAIN INDICATES
HIGHER STRESS STRAIN SHARPty DEPARTS
'-. FROM THE AXIS
< - 1^'- ~--^
BEFORE TEST
•CYCLE 188 F
^CYCLE 192 E
^CYCL E 193 E
TEST NO. 14 {i^= 106.9 pcf, K^= 1.0, cr^^' = 4100 psf)
Figure 167. Cyclic Triaxial Test Records for Monterey "0" Sand
265
a:
o o
o —
> >
O UJ
Q
(/)
^-4000
(/)
a.
Ijj
tr
'q. 0
<
cc
4000-
-10-
I
uJ 0-
5-
mm\.
P-
m
TEST NO, 16
Xd = 138.2 pcf
CTjc - 4100 psf
BEFORE TEST
* CYCLE 2E
* CYCLE 5E
J
SB
1
"l^
Figure 168. Cyclic Triaxial Test Records for Oroville Sand
266
UJ 4100-
'-■i. .: :::V-^'~r-T:' I- T ■■■!-
CHARACTERISTIC
PORE PRESSURE
PEAK
CHARACTERISTIC
LOAD PEAK
O o.
< b
> 6000-
STRAIN INDICATES
HIGHER STRESS -^
STRAIN SHARPLY
DAPARTS FROM
THE AXIS
BEFORE TEST
# CYCLE 14 E
)(■ CYCLE 26 E
m
m
}
^ Mm"^
i
IJU
1
'« jEji
o
r'
1 "^^^^ -m=
1 -
TEST NO. 25 ( Kq = 142.9 pcf, Kc = 1.0, (r ^^ ^100 psf)
Figure 169. Cyclic Triaxial Test Records for Oroville Sand
267
Analysis of Test Results
Extension Strain
The results of the cyclic tests show
that predominant extension strain is
not unusual for isotropically-
consolidated samples of dense, cohesion-
less material. Visual observations show
that this behavior is not a result of
necking.
Analysis of cyclic triaxial test rec-
ords produced by Mulilis et al (1975)
and other testing programs reveals that
the extension strain is consistently
greater than the compression strain.
This effect increases with increasing
density so that very dense samples
strain almost totally in the extension
direction.
The asymmetry could possibly be ex-
plained by the inherent limitations of
the test. The stress conditions do not
have the same relative values during the
extension and compression halves of the
stress cycle. Samples of higher dens-
ities require higher cyclic stress ra-
tios to cause significant strain levels.
With higher cyclic stress ratios, the
stress conditions in the two halves of
the stress cycle become more asymmetric.
This would explain why the extension
strain becomes more pronounced than the
compression strain for higher densities.
Although the extension direction is
weaker than the compression direction,
an average of the two strains produced
seems to be appropriate because it has
been successfully related to cyclic sim-
ple shear conditions (see Figures 175
and 176).
Necking Behavior
The cause of necking is theorized to be
non-uniformities and stress concentra-
tions with the sample. As cycling con-
tinues, the sample strains and will
eventually develop a stress concentra-
tion until all the axial strain occurs
primarily in one location and the sam-
ple necks. As the uniformity of the
sample increases, a higher number of
cycles is required to cause necking.
This would explain why the more uniform
Monterey "0" sand samples held together
better than the Oroville sand samples.
Necking can sometimes be detected in
the test records alone. This is be-
cause drastic necking leaves charac-
teristic readings in the pore pressure,
strain, and loading measurements.
These characteristic readings are illus-
trated for both materials in Figures
167 through 169 and include:
1. A sharp increase in the extension
strain.
2. The strain goes significantly into
extension during compression loading.
3. The pore water pressure drop during
extension loading increases.
4. Pore water pressure and axial load
records develop characteristic shapes
during the final stage of necking,
when the sample separates.
These necking symptoms develop only dur-
ing drastic necking. The samples may
develop necks of smaller magnitudes
without producing these symptoms. With-
out producing detectable symptoms in
the test records, severe necking has
been observed in the samples as far
back as 12 cycles before complete separ-
ation. Symptoms of drastic necking have
also been found in some of the test rec-
ords for the modeled Oroville gravel
samples. This leads to the conclusion
that some of the modeled Oroville grav-
el samples developed drastic necking.
Examples of the test records where
drastic necking has been found are shown
in Figures 170 through 172.
Sample "Tension"
Many sand samples were tested well be-
yond the "tension" boundary of 0.5 cyc-
lic stress ratio, but still behaved like
samples tested at lower stress ratios.
268
CHARACTERISTIC PORE
PRESSURE PEAK
CHARACTERISTIC
LOAD PEAK
TEST NO 37
y^ - 148.0 pc.f.
K^ = I 0
= 28700 p s f
STRAIN SHARPLY DEPARTS
FROM THE AXIS
Figure 170. Cyclic Triaxial Test Records for Modeled Oroville Gravel
53300
UI
3 In
" °- 26650
CHARACTERISTIC PORE
PRESSURE PEAK
CHARACTERISTIC
LOAD PEAK-
TEST NO 65
/■<) = 148.6 pcf
Kj =1 0
o-jj' = 53,300
SHARP INCREASE IN
EXTENSION STRAIN-
51-
Figure 171
STRAIN SHARPLY DEPARTS
FROM THE AXIS
Cyclic Triaxial Test Records for Modeled Oroville Gravel
269
hi
q:
o
h-
Q.
_l
co
1
a
>
tr
u
o
1-
<
b
53 300 1-
26650
-26 650
-53300>-
-4l00i-
4 lOOL-
EXTENSION PORE
PRESSURE PEAKS
BEGIN TO DECREASE
CHARACTERISTIC
PORE PRESSURE
PEAK
CHARACTERISTIC
LOAD PEAK
TEST NO. 69
Ya = 148.9 pcf
Kc = 10
o-jg' = 53 000 psf
5"-
STRAIN SHARPLY
DEPARTS FROM
THE AXIS
Figure 172. Cyclic Triaxial Test Records for Modeled Oroville Gravel
This Is because the designation of a
cyclic stress ratio of 0.5 as the bound-
ary for sample "tension" and cap lift-
off has little meaning. This definition
was probably developed assuming that
when the cyclic stress ratio was greater
than 0.5, the extension stress would be
greater than the effective confining
pressure and the sample cap would have
to lift off. This would be a total
stress definition. Soil behavior, how-
ever, is controlled by effective stresses
270
The idea of a constant "tension" bound-
ary throughout a cyclic triaxial test
is incorrect. During a cyclic triaxial
test, the residual pore water pressure
at the end of each complete stress cycle
tends to increase with each applied
cycle. As the residual pore pressure
approaches the chamber pressure, the
effective confining pressure is reduced.
The cyclic load, however, remains con-
stant. Thus, if an isotropically con-
solidated sample is cycled long enough
to approach initial liquefaction, it
experiences a "tension" condition re-
gardless of the cyclic stress ratio
being applied.
The question that must be addressed is
why does the sample hold together during
"tension" and how does this relate to
actual soil behavior during earthquake
loading .
First it should be noted that the static
extension test produced normal uniform
sample behavior up to a stress ratio
(a(jp/2a'o ) of 1.0; and could have gone
higher if a higher back-pressure had
been used.
In Figures 167 through 172, which show
cyclic test results, the pore water
pressure develops into a repetitive
steady-state pattern after the first
few cycles. Examination of the steady-
state pore pressure patterns presented
reveals that, as the cyclic stress
curve crosses the zero axis, the pore
pressure approaches the chamber pres-
sure, and the effective confining pres-
sure drops to virtually zero. At this
time, the sample begins to strain quite
rapidly. As the sample strains, the
pore pressure begins to drop and the
sample strain begins to level off. Most
of the strain develops at relatively low
percentages of the applied stress. This
behavior is the same for both extension
and compression halves of the stress
cycle. The main differences between the
two halves of the stress cycle during
this steady-state pore pressure pattern
are in the magnitudes of the pore pres-
sure drop and the amounts of axial
-15000' \—
Kc = 10
>^d = 106.7 pcf
o-j'j.: 4100 psf
Figure 173. Extension/Compression Cycle
for Monterey "0" Sand Cyclic Triaxial
Test
271
strain. For cyclic triaxial tests on
dense isotropically consolidated sam-
ples, the axial strain is concentrated
in the extension direction, and the pore
pressure drop in the extension direction
is approximately four times the drop in
the compression direction.
The pore pressure drop is what holds the
sample together. Without the drop in
pore pressure, the sample would experi-
ence unlimited strain in either direc-
tion of loading. The drop in pore pres-
sure has often been explained by the
tendency of the sample to dilate. How-
ever, the drop in pore pressure during
the extension half of the stress cycle
could possibly be caused by an erroneous
feature of the cyclic triaxial test.
If the cap lifted off, the resistance
to extension loading would be a result
of suction on the water alone and not
represent actual sample behavior. Neck-
ing might not result; but the test would
no longer represent a shearing test. It
is very important to note that, if this
behavior exists, it exists for every
isotropically consolidated cyclic tri-
axial test that approaches initial
liquefaction.
Although the possibility of this erron-
eous "suction" behavior exists, it is
not believed responsible for the behav-
ior of the sample. Instead, it is pre-
sumed that the extension half of the
stress cycle is actually analogous to
lateral compression. This idea is sup-
ported by the fact that the extension
and compression halves of the stress
cycle yield similar patterns of pore
pressure change. In Figures 173 and
174 are detailed plots of single stress
cycles for two cyclic triaxial tests on
Isotropically-consolidated samples of
dense Monterey "0" sand. One cycle be-
gins with compression and the other be-
gins with extension. It may be seen
that a pore pressure rise occurs during
the initial loading in either direction.
Then, after the sample has experienced
axial strain, the pore pressure drops.
Although the magnitude of the drops are
different for the extension and compres-
sion directions, the general behavior
is the same. This same behavior is
shown in Figures 159 and 160, which de-
pict static extension and compression
test results. Every time axial stress
is applied in either direction, in sta-
tic or cyclic loading, the pore water
pressure rises first and then drops
with increasing strain.
The cyclic triaxial test behavior can
also be related to static test behavior
by the development of strain. Results
of studies by Mulilis, et al (1975),
DeAlba, et al (1975), Seed and Lee
(1966), and many others show that cyclic
triaxial tests develop higher strains
for samples composed of lower densities.
Examination of the static test results
presented in Figures 159 and 160 re-
veals that, to produce the same amount
of pore pressure drop, samples of lower
densities require much more strain.
The testing system that has been consi-
dered the best measure of the deforma-
tion potential of isotropically consoli-
dated samples is the large-scale simple
shear (shaking table) device. Compari-
sons between shaking-table and cyclic
triaxial test results carried out for
isotropically consolidated samples of
Monterey "0" sand are depicted in
Figures 175 and 176. The shaking-table
results are consistently weaker than the
results of the cyclic triaxial test.
The ratio of the two strengths ranges
between 0.5 and 0.6 for the conditions
depicted. This range of cyclic strength
ratios is consistent with the theoret-
ical range of 0.55 to 0.70 developed by
Seed and Peacock (1970) for the C cor-
rection needed to account for the diff-
erence in stress conditions.
The similar pore pressure tendencies
exhibited in both the static and cyclic
triaxial tests, the observed effects of
sample density on both static and cyc-
lic triaxial sample strains, similarity
of sample behavior at cyclic stress ra-
tios ( Oj /2a' n ) above and below 0.5,
dp Jc
272
15000
en
en
10000
LlI
a:
h-
(f)
5000
tr*-
oi^
H- I
< 1
0
> ^
U b
-5000
O
-I
o
>-
-10000
o
-15000
5000 t—
cn
to
UJ
cr
Q.
UJ '
I- 3
<:
-5 000
-10000
-10
Kc --I.0
}fd = 106.2 pcf
0-3 p' =4100 psf
Figure 1 7^+ . Compression/Extension Cycle for Monterey
Sand Cyclic Triaxial Test
273
INITIAL LIQUEFACTION
5% SHEAR STRAIN
Cr = 0.62 0.54
I
O 0.5-
T 1 1 1 1 1 1 1 r
10 30 50 70 90
10% SHEAR STRAIN
0.4-
w 0.3-
0.2-
0. I-
Cr = 0.53
15% SHEAR STRAIN
Cr= 0.51
0.5-
0.4-
1
0.3-
/t .
/
/
/
/
0.2-
/
/ /
/ /
/
0 1 -
/ y
/
^-
rill 1 1 1 1
Figure 1
for 5
RELATIVE DENSITY %
NOTES =
A = TRIAXIAL TEST (o-rip/2a-3c' ) - MULILIS ET AL (1975)
• = SHAKING TABLE TEST {T\,^/(t^) - DE ALBA ET AL(I975)
75. Comparison for Shaking Table and Cyclic Triaxial Test Results
Cycles
274
INITIAL LIQUEFACTION
5% SHEAR STRAIN
Cr=0.63
lo
I
o
q:
30 50 70
10% SHEAR STRAIN
0.5
LlJ 0.4
0.3
0.2
0.1
c
r=0.57
/
/^ 1 1 1 1 1 1 1 1
0.4 -
0.3
0.2 -
0.1 -
10 30 50 70 90
15% SHEAR STRAIN
0.5
Cr = 0.53
1
0.4
-
0.3
_
i
/
^/
0.2
/
y
/ ,^ 1
/ y
0.1
/ y^
/ ^^
^^ 1 1 1 1 1 1 1 1
30 50 70 90 10 30 50 70
RELATIVE DENSITY (%)
A = TRIAXIAL TEST ( Qjp / aCTjc ) - M ULI LI S ET AL (1975)
• = SHAKING TABLE TEST {Z^^/Q'^) -DE ALBA ET AL ( 1975)
Cr= (Fhv/CTo') / (CJdp/aj'c)
Figure 176. Comparison of Shaking Table and Cycle Triaxial Test Results for
10 Cycles
275
and the comparisons between the cyclic
triaxial test and shaking-table results
all indicate that the cyclic triaxial
test can be used to estimate the deform-
ation potential of a soil during cyclic
loading. In addition, the development
of a shear plane during cyclic loading
indicates that a shearing behavior is
indeed taking place. Since the question
of sample "tension" eventually occurs
in every sample, it would seem that cyc-
lic stress ratios greater than 0.5 are
just as valid as lower stress ratios.
Cyclic Strength Interpretations
Considered
Because of the uncertainties generated
by the cyclic triaxial tests performed
for the modeled Oroville gravel samples,
two different strength interpretations
were considered. The two interpreta-
tions are contrasted by different judg-
ments concerning strain development.
Strength interpretation I was based up-
on the observation that the isotropical-
ly consolidated gravel samples did not
seem to develop significant strain
levels at low confining pressures and
that the static strength might be appro-
priate to use at these consolidation
stresses. Strength interpretation II
was developed using the results of the
laboratory investigation of dense sands
to interpret and extrapolate the test
results of the modeled Oroville gravel
samples.
Strength Interpretation I
The results of the cyclic triaxial tests
for the modeled Oroville gravel are sum-
marized in Appendix K. The assumptions
used in defining the strain levels, load
levels, corrections, and other para-
meters will be included in the final
report on testing (Appendix L) , which
will be available on request when
completed.
The results of these tests were convert-
ed into the cyclic strength envelopes
shown in Figure 177. The strengths are
designated as the shear stress required
to cause a specified strain in six cyc-
les. A C correction of 0.6 for tests
with K^ = 1, and a (ji'of 41.5° were used
in the conversion.
Static undrained strength results were
used to define the cyclic strengths for
alpha values of 0 and 0.1 at low consol-
idation pressures because:
1. The samples that were isotropically
consolidated at 196 and 784 kilopas-
cals (41,000 and 16,400 psf) devel-
oped only a limited amount of strain
— generally less than +5 percent.
2, The critical confining pressure is
about 800 kilopascals (about 17,000
psf) based on static triaxial tests
done by the U. S. Army Corps of
Engineers in 1964.
At consolidation pressures lower than
the critical confining pressure, static
test samples have very high strength
because negative pore pressure develops.
The basic assumption of interpretation
I is that negative pore pressure will
also develop in cyclic tests, and there-
fore the cyclic strength has to be as
high as static strength. This assump-
tion seems to be verified by the limit-
ed strains that developed in cyclic
tests at low consolidation pressures.
Strength Interpretation II
The assumption for interpretation I is
probably valid for liquefaction consid-
erations, i.e., at confining pressures
less than critical, a cohesionless ma-
terial probably will not liquefy if sub-
jected to cyclic stresses lower than the
static shear strength. However, lique-
faction is not a concern for the Oro-
ville gravels. The cyclic triaxial
samples never showed any tendencies to
develop sudden unlimited strains. The
objective of the cylic testing was to
define strain behavior as related to
consolidation stress conditions and
cyclic stress levels.
276
As shown in Figures 159 and 160, posi-
tive pore pressure develops at low
strain levels in static tests, even for
very dense samples and low consolida-
tion pressure. Furthermore, in the
shaking table tests reported by DeAlba,
positive pore pressures developed and
eventually reached the value of the
overburden pressure. In both cases,
the pore pressure then decreased during
further increase in strain. The pore
pressure drop is the mechanism which
prevents liquefaction. However, the
sample can strain to an extent consis-
tent with the effective stresses that
develop.
Cyclic triaxial test behavior was comp-
licated by the severe load attenuation
and necking problems encountered in the
testing program. For example, many of
the samples that did not develop large
amoimts of strain had either significant
load attenuation or were not tested to
large numbers of cycles. Tests at the
higher consolidation pressures that did
develop large strains also exhibited
symptons of necking behavior.
If the samples consolidated at the lower
consolidation pressures were tested at
higher stresses and numbers of cycles,
higher cyclic strain levels would have
been produced. Based on the tests of
dense Monterey "0" sand, cyclic strain
would be expected to increase propor-
tionately with an increase in cyclic
stress. This would not lead to a sud-
den jump in shear strength envelope as
is the case for interpretation I. Thus,
it is probable that the actual cyclic
strength values at alphas of 0.0 and 0.1
at the lower confining pressures are not
as high as the static strength values
presented in Figure 177.
The second strength interpretation was
developed from the cylclic triaxial test
records. It was assumed that the in-
crease in strength due to the calibra-
tion error canceled out the reduction
in strength due to the membrane correc-
tions. However, the consolidation
stress ratios (K ) were corrected for
the calibration change. This assumption
was judged to be conservative.
Axial strain was defined as follows:
cumulative peak compressive strain for
anisotropically consolidated samples;
one-half peak to peak strain for iso-
tropically consolidated samples. For
tests with load attenuation or necking,
strain curves were extrapolated to high-
er cycles based on the early portions
of the tests (prenecking or preattenu-
ation). Typical extrapolations of
strain are shown in Figure 178.
The conservatism shown in the figure was
used to account for the severe load at-
tenuation and necking behavior experi-
enced in the isotropically consolidated
cyclic tests. The strain extrapolations
for the remaining tests are shown in
Appendix H. Presented in Appendix I are
the cyclic-stress vs. number-of-cycles
curves developed for this second strength
interpretation .
The resulting cyclic strength envelopes
for 5- and 10-percent strain in 10 cyc-
les are shown in Figure 179. The proce-
dures used in developing these cyclic
strength envelopes are illustrated in
Appendix J. AC correction of 0.63
(for K =1.0 tests), and a *'of 44°
were used in the conversion. It should
be noted that this second strength in-
terpretation is judged to be conserva-
tive, because cyclic strain envelopes
have a tendency to level off as cycling
continues. A straight line extrapola-
tion, therefore, can be considered
relatively conservative.
277
2.5 7o RESIDUAL AXIAL STRAIN IN 6 CYCLES
10
, _ -, r r- <
.
_^_^
^^j^^^^]Lj^ —
"
^=06,^
^::::^^
H
^=a£jji.
5 10 15 20 25 30 35 40
NORMAL STRESS ON FAILURE PLANE DURING CONSOLIDATION O^c^^q /<=m2
_i
Q.
LlI
o> 6
5% RESIDUAL AXIAL STRAIN IN 6 CYCLES
_-— J
A
)
\
^'-^
^^^
^\ -— '
,^'-— ^
\
-"""6:
, q7 , Cr
\ ^
<;^
^^=00,0132-
-"■■"^
::^
.*'^^^^"
\^--^
10
15
20
25
30
NORMAL STRESS ON FAILURE PLANE DURING CONSOLi DATiON , 0",c, K- /cm^
35 40
10% RESIDUAL AXIAL STRAIN IN 6 CYCLES
I-
c/-:^^
br^
— ■ —
\
^ — '
\
v^^
^.---^
^^oo^
.36- — '
—
^
^
<^
^
-^^^
\.
^
,<^
5 10 15 20 25 30 35 40
NORMAL STRESS ON FAILURE PLANE DURING CONSOLl DATION , CTfc.Kq /cm^
Figure 177. Cyclic Strength Envelopes for Strength Interpretation I -
Static and Cyclic Test Results
278
-20
-15 -
,-10-
^2.5
'10
= 6
= 9
= 27
AMPLE PRESUMED
NECKED
TEST NO. II
K, = 1.0
-4-
-+-
ID 15 20
NUMBER OF CYCLES
25
PREDOMINANT AXIAL CYCLIC STRESS a: ± 10900 psf
FOR FIRST CYCLES
10
-20
TEST NO. 76
Kc =1.0
CTj^' = 16400 psf
50 75 100
NUMBER OF CYCLES
125
PREDOMINANT AXIAL CYCLIC ST RESS =» ± 7000 psf
FOR FIRST CYCLES
10
Figure 178. Typical Extrapolations of I sotropi cal 1 y -Consol idated Cycl Ic
Triaxial Tests on Modeled Oroville Gravel
279
•20000
1 1 1 1 1 r
5% COMPRESSIVE STRAIN IN 10 CYCLES -{
0 20000 40000 60000
NORMAL STRESS ON FAILURE PLANE
DURING CONSOLIDATION
( psf )
20000
CO -^
ir> a.
16 000
iij s.
^<
en '
UJ
12000
en 2
< <
UJ _)
I a.
<n
8000
UJ
u fr
"i =>
o -J
4000
20000 40000 60000
NORMAL STRESS ON FAILURE PLANE
DURING CONSOLIDATION, o-,^ ( psf )
Figure 179. Cyclic Strength Envelopes for Strength
Interpretation II - Extrapolated Cyclic Test Results
280
9. EVALUATION OF PERFORMANCE
General Considerations
Method of Evaluation
So far, this chapter has dealt mostly
with the concerted efforts to determine
the input properties and conditions for
a complete dynamic evaluation of embank-
ment performance during the Reanalysis
Earthquake. A fairly wide range of in-
terpretations was possible for dynamic
shear modulus and cyclic shear strength.
Other properties were found to have
only a minor effect on computed stress-
es. Thus, even though the procedures
used are sophisticated — the current
state-of-the-art — the inability to
define all input properties closely
limits the confidence level of the
results.
This is not meant to imply that the
dynamic analysis procedures are infer-
ior to other methods of evaluating seis-
mic performance of dams. It is only
meant to emphasize that a fairly wide
range of answers will often be found,
even with the most diligent efforts to
measure or otherwise determine dynamic
material properties and other conditions
affecting embankment behavior. Gener-
ally, other methods of analysis suffer
the same limitations as dynamic analysis
procedures, plus additional shortcomings
of their own. Carefully documented ob-
servations of dam performance during
strong earthquakes are needed.
Meanwhile, each engineer tries to apply
the lessons learned from the few dams
shaken by moderately strong earthquakes.
Unfortunately, there is not always
agreement among dam design engineers on
just what the lessons are from a given
set of observations. One area of gener-
al agreement is that evaluation of seis-
mic stability of dams requires the exer-
cise of sound judgment by engineers ex-
perienced in dam design.
The seismic stability analysis of an
earth dam involves four major steps:
1. Determine the stresses induced into
the soil in the field — both static
and dynamic.
2. Simulate as closely as possible these
stresses on samples of similar soil
in the laboratory and observe the
behavior.
3. Extrapolate back from the laboratory
to the field to estimate probable be-
havior of the actual earth dam.
4. Compare the predicted performance of
the dam with established criteria for
acceptability.
The static and dynamic stress analyses
and the laboratory testing have already
been discussed in Sections 4, 7 and 8.
The remainder of this section deals
with steps 3 and 4.
Two assumptions are needed to relate
test sample stresses to field stresses
— that the failure planes are known
in both cases, and that the irregular
field stress time history can be repre-
sented by an equivalent uniform stress
time history.
Failure Planes
It is assumed that horizontal planes in
field elements should be related to
failure planes in test samples. For
consolidation conditions, normal and
shear stresses must be the same on field
horizontal planes and sample failure
planes. For cyclic loading conditions,
cyclic shear stresses on these planes
are compared in order to relate field
281
behavior to test sample behavior.
This comparison is usually in the form
of a safety factor or strain potential
for each field element. Either form is
a measure of the amount of strain that
a test sample would develop if subjected
to the same stress history as the field
element.
For triaxial test samples consolidated
anistropically, the failure plane is
assumed to be inclined at an angle of
4) = 45 + (|)'/2 degrees from the major
principal plane. For samples consoli-
dated isotropically, ^ is assumed to be
45 degrees, and the correction factor
C is used to account for the inability
of the triaxial test to duplicate all
the field stresses correctly.
Equivalent Regular Stress Time History
Two procedures have been developed for
converting an irregular shear-stress
time history to an equivalent regular
shear-stress time history (Lee and Chan,
1972, and Seed et al, 1975). Both pro-
cedures were derived from essentially
the same basic assumption — that the
irregular, and equivalent regular,
stress patterns would produce the same
accumulated strain. The amount of
strain produced by each cycle is related
to the stress level of the cycle and as-
sumed to be independent of its location
within the time history. However, stud-
ies by Harder (1977) show that computed
equivalent regular stresses may vary by
as much as 30 percent, depending on the
location of the higher peaks within the
irregular pattern.
Weighting curves are used to determine
the relative contribution of each cycle.
The cylic stress (t ) vs. number of cyc-
les (N) curves from the cyclic tests
are used as weighting curves. Each lo-
cation (element) within the embankment
requires a different T vs. N curve
specifically for the consolidation
stress conditions of that location,
thus requiring many interpolations from
the test curves. Also, triaxial test
curves have different shapes than do
simple shear test curves.
Variations in choice of procedures,
weighting curve interpolations, and
test method can lead to different re-
sults. To remedy this situation. Seed
et al^ (1975), have presented a universal
weighting curve based on large-scale
shaking-table tests on sand.
This curve, shown in Figure 180, was
used in the calculations of equivalent
uniform shear-stress time histories.
Two different combinations of regular
stress level and number of cycles at
this level were computed :
Combination No.
12 1
Ratio of regular stress to peak
irregular stress
0.65
0.5
Number of regular stress cycles 6
Combination No. 2 was used in the performance evaluations.
10
No attempt was made in this study to
account for the location of the larger
stress peaks within the time history.
Cases Analyzed and Assumptions
One assumption made at the beginning of
this study was that only the submerged
upstream shell would be of concern.
The downstream shell is unsaturated and
is assumed to have essentially full sta-
tic drained strength, which is much
greater than the cyclic undrained
strength of the upstream shell. Equal-
ly pertinent, observations of embankment
performance in earthquakes, theory, and
judgment all lead to the conclusion that
a well-compacted, dry rockfill or gravel
282
1. STRESS LEVEL, T/Tmax.
2. NUMBER OF CYCLES REQUIRED TO CAUSE
LIQUEFACTION, N.
3. STRESS LEVEL WITH SAFETY FACTOR OF L5 ON rmax(%)
4 LABORATORY TEST VALUES REDUCED TO ACHIEVE A
SAFETY FACTOR OF L5.
5 ORIGINAL LABORATORY TEST VALUES FOR CYCLIC SIMPLE
■ SHEAR TESTS T -SHEAR STRESS , r ^ax. MAXIMUM
SHEAR STRESS.
- 100
®
500 1000
Figure l80. Representative
Required to Cause Liquefaction (Seed et al , 1975)
Relationship Between t/t and Number of Cycles
283
embankment will perform well in a strong
earthquake.
The core is a well-compacted, clay-
gravel material. It should perform as
well as compacted clay embankments that
have withstood strong earthquake shaking
without any detrimental effects (Seed
et al, 1978).
Many of the input properties and anal-
ysis conditions could vary over a wide
range without significantly affecting
the predicted behavior. Some, such as
material density, are well defined.
However, there are four items which can
vary over a wide range, which have a
major effect on the predicted behavior,
and on which there are differences in
opinion as to the best defined or most
reasonable value:
1. Dynamic shear modulus of shell
material.
2. Cyclic shear strength of upstream
shell material.
3. Abutment restraint (3D) effects on
dynamic shear stresses.
4. Degree of drainage in the upstream
shell during earthquake shaking.
The influence of items 1 and 3 on stress-
es has already been examined in Section
7. On item 2, two different strength
interpretations have been discussed in
Section 8. Item 4, drainage, has not
been discussed previously, but it was
observed in Section 3 that in the Aug-
ust 1 earthquake, pore pressure in the
upstream transition rose 90 kilopascals
(13 psi) and then dissipated during the
six second gap in the record.
Strain potentials in the upstream shell
were computed for four cases involving
different assumptions for these proper-
ties and conditions. Other properties
and conditions were either well defined
or were chosen from the conservative end
of the defined range. (Conservative
means that the value chosen produces the
highest strain potential of any value
in the range.) The rationale for each
case is supportable, and to a large de-
gree is a matter of judgment, or of
philosophy in dealing with level of
risk. Strain potential contours for
all four cases are shown in Appendix M.
Case a
Shell K = 165
Strength Interpretation II (lower),
but with consideration of effect
of conservatism in data extra-
polations and of possible strength-
ening effect of seismic history.
Abutment restraint (3D) effects
included.
Drainage effects considered
qualitatively.
In the authors' judgment, these values
and conditions are the most supportable
choices based on considerations of the
data and evidence developed in this
study, and many other studies over the
last few years. Case a is called the
"best judgment case."
Case b
Shell K ^ = 205
Strength interpretation II (lower)
Abutment restraint (3D) effects NOT
included
NO drainage
Each of these choices is at the end of
the defined range which produces the
higher estimated displacement. Case b
is called the "conservative case."
Case c
Shell K^^ ^ = 205
Strength™ Interpretation I (higher)
Abutment restraint (3D) effects NOT
included
NO drainage
The choices for the first two items
represent the viewpoint of some of the
many engineers who contributed to this
study. For the last two items, the
284
usual conservative assumptions were
used.
Case d
Shell K X " -^-^^
Strength interpretation II (lower)
Abutment restraint (3D) effects NOT
included
NO drainage
For the last two items the usual conser-
vative assumptions were used. The first
two items are from cyclic triaxial tests
of 30-centimetre (12-inch) remolded sam-
ples. Several studies have shown that
dynamic strength and shear modulus are
higher in situ than in remolded samples.
The assumption is that the strength and
modulus from the tests, although both
too low, give about the same strain
potentials as the correct in situ
strength and modulus would give.
Comparison of Cases
Cases c and d result in slightly higher
strain potentials than case a; case b
strain potentials are substantially
higher than any of the other three.
Therefore only cases a and b will be
considered further in assessing be-
havior of the dam.
Predicted Behavior - Best Judgment Case
The best judgment choices of input
values and conditions have already been
described. The reasoning for these
choices is presented here.
The predicted behavior is the assessment
of permanent displacements that the re-
analysis earthquake would cause in the
upstream shell.
Shell K,
2max
Two extrapolations were made to extend
the natural period ratio curve to L/H of
7. The more consistent one gives a per-
iod ratio of 1.35 (Figure 125). The
corresponding 2D period is 1.1 seconds,
and range of K- is 135 to 165
(Figure 128). ^'"^''
Cyclic Shear Strength
There is probably some conservatism in
the use of remolded samples to represent
the behavior of in-place materials —
even though the two-month aging tests
did not indicate a gain in strength.
For example, the recent past seismic
history probably strengthened the gravel
shell material against possible future
earthquakes.
Also, there is some conservatism in the
extrapolation of the cyclic strain en-
velopes for Strength Interpretation II.
Three-Dimensional Effect
Both Makdisi's work and analyses of this
study indicate that lower shear stresses
will develop for three-dimensional con-
ditions than for two-dimensional condi-
tions — particularly in the area of
higher strain potentials in the upper
part of the shell. Makdisi's results
for a narrower canyon (L/H = 3) than
Oroville give 0 to 75 percent lower
stresses. Estimates by this study for
the actual Oroville Canyon (L/H = 7)
give about 20 percent lower stresses.
The San Fernando Dams should have had
a much smaller or negligible 3D effect
because the L/H were 12 and 13. There-
fore, it is assumed that the 3D effect
is not "built in" to the procedure
which was developed and tested against
the observed earthquake performance of
the San Fernando Dams.
Drainage
All the strength evaluations are based
on the assumption of completely un-
drained conditions in the upstream
shell. However, drainage does take
place as indicated by the rapid dissi-
pation of the pore pressure developed
in the August 1, 1975 earthquake. At
cell No. 1, a cyclic pore pressure of
90 kilopascals (13 psi) developed early
and dissipated during the six-second gap
in the records. This cell is located in
the upstream transition zone near the
core, and indicates that the gravel shell
285
and transition do experience some degree
of drainage during earthquake shaking,
even in interior locations. Drainage
relief of pore pressures presumably
would be greater at locations closer to
the surface of the slope, where the
strain potentials tend to be higher.
Predicted Behavior
Stresses were calculated for a shell
^2max °^ ^^^ corresponding to the 1.1
PSEUDO THREE DIMENSIONAL ANALYSI
PSEUDO Kg MAX =350
PSEUDO CORE Gmax/Su = 1750
SHELL K2MAX = 165
CORE G /S = 2200
second natural period, and for the three
dimensional effect (abutment restraint).
As shown in Figure 181, the resulting
compressive strain potentials are less
than 5 percent except for a small zone
in the middle of the upstream shell.
This would generally be regarded by dam
design engineers as indicating accept-
able behavior involving only minor
displacements .
PREDICTED FOR BEST JUDGMENT CASE
NOTES ■■
REANALYSIS EARTHQUAKE
COMPUTER PROGRAM LUSH
CYCLIC STRENGTH INTERPRETATION H - EXTRAPOLATED CYCLIC
TRIAXIAL TEST RESULTS
UNDRAINED CONDITIONS
Figure l8l. Computed Compressive Strain Potentials in Upstream Shell - Percent
Calculations were not made for the ef-
fect of higher strength or drainage be-
cause information is not complete enough
to quantify these factors. However,
the strain potentials would be even
lower, and could be described as less
than 5 percent everywhere in the up-
stream shell.
An interesting question here is what
displacements would result from the
method of calculation used at Upper San
Fernando Dam. If average compressive
strain is assumed to be 2 percent, then
average shear strain is only 3 percent,
and a 91-metre (300-feet) high section
would produce a surface displacement
of 2.7 metres (9 feet), which is not
what most engineers would think of as
minor displacement.
It may well be that the method of cal-
culating displacement applies to cases
with high strain potentials and lique-
faction, as at Upper San Fernando Dam,
but does not apply to cases with low
strain potentials and no liquefaction.
It may also be that dams of great
height would experience substantial dis-
placements corresponding to low strain
levels, and that not enough experience
is available with earthquake performance
to realize it. It is likely a little
of both.
286
From all the considerations discussed,
it is concluded that compressive strain
potentials will be small — less than
5 percent — and that no slides or
"large" movements will develop. It is
not so clear just how "large" might be
the displacments associated with the
predicted strain potentials. Because of
the great height of the dam, it is con-
sidered conceivable that permanent dis-
placements on the order of a metre could
develop at the surface of the upstream
slope as a result of the small shear
strains within the upstream shell.
Estimated Displacements for Conservative
Assumptions
The predicted behavior for the best
judgment case is considered conservative
in many respects, and the possibility of
greater displacements is considered re-
mote. Nevertheless, it is worthwhile
to check this remote possibility to see
how bad the situation would be if soil
properties and conditions proved to be
more adverse than the best judgment
choices. The four pertinent input val-
ues and conditions for the conservative
case were:
- horizontal displacement of the
surface by a few tens of feet
in the interval between the two
berms.
- slumping of the shell material
near the upper berm.
- bulging of the shell material
near the lower berm.
The displacement and slumping would be
limited to the upstream shell material.
Slumping would not be expected to extend
upslope to the crest (judgment based on
extent of slumping at Lower San Fernando
Dam) . The compacted gravel in the up-
stream shell would be as strong and per-
form as well after deformation as
before.
Based on the behavior of triaxial test
samples, there is no concern over sudden
massive shear slides or liquefaction
flow slides. Movement would occur only
in short-duration increments and only
during the highest peaks of earthquake
acceleration, the several increments
accumulating to a total of perhaps
10 metres.
Shell K^^ = 205
Strength Interpretation II (lower)
Abutment restraint (3D) effects
NOT included
No drainage
The strain potential pattern and the
method of estimating displacements are
included in Appendix M. The extreme of
deformations of the upstream slope
might be as follows :
Remember that this is the most extreme
case that could be supported by the re-
sults of the analysis — by adopting
simultaneously the most conservative
values for material properties and other
input conditions. Although these post-
ulated movements are uncomfortably
large, they would not threaten the
safety of the dam.
287
REFERENCES
Becker, E., Chan, C. K. and Seed, H. B. "Strength and Deformation Characteristics
of Rockfill Materials in Plane Strain and Triaxial Compression Tests".
Report No. TE 72-3 to State of California, Department of Water Resources.
1972
Bolt, Bruce A. "Duration of Strong Ground Motion". Proceedings - Fifth World
Conference on Earthquake Engineering. Rome, 1974.
DeAlba, P., Chan, C. K. and Seed, H. B. "Determination of Soil Liquefaction
Characteristics by Large-Scale Laboratory Tests". Report No. EERC 75-14.
University of California, Berkeley. 1975
Harder, Leslie F., Jr. "Liquefaction of Sand Under Irregular Loading Conditions".
Thesis, submitted in partial satisfaction of requirements for the Degree of
Master of Science in Engineering, Graduate Division, University of California,
Davis. 1977.
Idriss, I. M. , Lysmer, J., Hwang, R. and Seed, H. B. "A Computer Program for
Evaluating the Seismic Response of Soil Structures by Variable Damping Finite
Element Procedures". Report No. EERC 73-16. University of California,
Berkeley. 1973.
Kulhawy, F. H. and Duncan, J. M. "Nonlinear Finite Element Analysis of Stresses
and Movements in Oroville Dam". Report No. TE 70-2 to State of California,
Department of Water Resources. 1970.
Lee, Kenneth L. and Kwok Chan. "Number of Equivalent Significant Cycles in Strong
Motion Earthquakes". Proceedings, Conference on Microzonation for Safer Con-
struction, Seattle. November 1970.
Lowe, J. "Shear Strength of Coarse Embankment Dam Materials". Proceedings, 8th
Congress on Large Dams, pp. 745-761. 1964.
Lysmer, J., Udaka, T., Seed, H. B. and Hwang, R. "LUSH - A Computer Program for
Complex Response Analysis of Soil-Structure Systems". Report No. EERC 74-4.
University of California, Berkeley. 1974.
Makdisi, F. I. "Performance and Analysis of Earth Dams During Strong Earthquakes".
Dissertation, submitted in partial satisfaction of the requirements for the
Degree of Doctor of Philosphy in Engineering, Graduate Division, University
of California, Berkeley. 1976.
Marachi, N. D., Chan, C. K. , Seed, H. B. and Duncan, J. M., "Strength and Deforma-
tion Characteristics of Rockfill Materials". Report No. TE 69-5 to State of
California Department of Water Resources. 1969.
Mulilis, J. D., Chan, C. K. and Seed, H. B. "The Effects of Method of Sample
Preparation on the Cyclic Stress-Strain Behavior of Sands". Report
No. EERC 75-18. University of California, Berkeley, 1975.
288
REFERENCES (Continued)
Nobari, E. S. and Duncan, J. M. "Effect of Reservoir Filling on Stresses and
Movements in Earth and Rockfill Dams". Report No. TE-72-1. University of
California, Berkeley. 1972.
Schnabel, Per B. and Seed, H. Bolton. "Accelerations in Rock for Earthquakes in
the Western United States". Bulletin, Seismological Society of America.
Volume 63. 1973.
Seed, H. Bolton. "Evaluation of Soil Liquefaction Effects on Level Ground During
Earthquakes". State-of-the-art paper presented at Symposium on Soil Liquefac-
tion, ASCE National Convention, Philadelphia. October 2, 1976.
Seed, H. Bolton and Idriss, I. M. "Soil Moduli and Damping Factors for Dynamic
Response Analysis". Report No. EERC 70-10. University of California,
Berkeley. 1970.
Seed, H. Bolton, Idriss, I. M. and Kiefer, Fred W. "Characteristics of Rock Motions
During Earthquakes". Journal, SMFE. September 1969.
Seed, H. B., Idriss, I. M. , Makdisi, F. and Banerjee, H. "Representation of
Irregular Stress Time Histories by Equivalent Uniform Stress Series in
Liquefaction Analyses". Report No. EERC 75-29. University of California,
Berkeley. 1975.
Seed, H. Bolton and Lee, Kenneth L. "Liquefaction of Saturated Sands During Cyclic
Loading". Journal of the Soil Mechanics and Foundations Division, ASCE.
Vol. 92, No. SM6, Proc. Paper 4972, pp. 105-134. November 1966.
Seed, H. B., Lee, K. L., Idriss, I. M. and Makdisi, F. "Analysis of the Slides
in the San Fernando Dams During the Earthquake of February 9, 1971". Report
No. EERC 73-2. University of California, Berkeley. 1973.
Seed, H. Bolton, Makdisi, Faiz, I., and DeAlba, Pedro "Performance of Earth Dams
During Earthquakes". Journal of the Geotechnical Engineering Division, ASCE.
Volume 104, No. GT7, Proc. Paper 13870, pp. 967-994. July 1978.
Seed, H. Bolton and Peacock, W. H. "Applicability of Laboratory Test Procedures
for Measuring Soil Liquefaction Characteristics Under Cyclic Loading". Report
No. EERC 70-8. University of California, Berkeley. 1970.
U. S. Bureau of Reclamation. "Dynamic Analysis of Embankment Dams". For Submission
to the International Commission on Large Dams for Publications as a State-of-
the Art Paper. 1976.
Vrymoed, John, et al. "Dynamic Analysis of Oroville Dam". Final Draft of Office
Report, Department of Water Resources, Division of Safety of Dams. June 1978.
Wong, R. T. "Deformation Characteristics of Gravels and Gravelly Soils Under Cyclic
Loading Conditions". Dissertation, submitted in partial satisfaction of the
requirements for the Degree of Doctor of Philosophy in Engineering, Graduate
Division, University of California, Berkeley. 1973.
289
CHAPTER VI
SEISMIC ANALYSIS OF THE OROVILLE
DAM FLOOD CONTROL OUTLET STRUCTURE
Commentary
As a result of the August 1, 1975 Oro-
ville earthquake, of magnitude 5.7, the
Department found it appropriate to reana-
lyze the Oroville Dam Flood Control Out-
let structure (Figures 182 and 183)
using a stronger earthquake (magnitude
6.5) and the latest techniques in seis-
mic investigation.
A seismic study, monitored by the Depart-
ment, was conducted under a consulting
agreement between Dr. Edward L. Wilson
and the Department of Water Resources.
The results were presented in the report,
"Earthquake Analysis of the Oroville
Dam Flood Control Outlet Structure",
by Edward L. Wilson, Frederick E.
Peterson, and Ashraf Habibullah. Their
report is included as the final part of
this chapter.
The finite-element method and dynamic
techniques were utilized in this study
to perform a lineraly elastic three-
dimensional analysis of the reinforced-
concrete structure. The three-
dimensional analysis was chosen because
of the complexity of the structure. In
this analysis, dead and hydrostatic
loads were applied to the same finite-
element model; the interaction of the
reservoir was not included due to limi-
tations of the present state of the art.
However, to include the full participa-
tion of the reservoir, a finite-element
two-dimensional analysis with hydro-
dynamic interaction was also performed.
This resulted in stresses approximately
20 percent higher.
The modified Pacoima and Taft, 6.5 magni-
tude earthquake accelerogram (see
Chapter V) , was used in these analyses.
Horizontal acceleration of the ground
was applied parallel to the outlet
centerline. This produced the largest
stresses in the piers.
The effects of a horizontal acceleration
in the transverse direction were exam-
ined by the Department. For this case
the piers were assumed fixed at the
breast wall and bottom slab. Displace-
ment of the supports equal to the width
of two contraction joints was assumed.
Stresses produced were below allowable
working stresses and therefore no
further investigation for this case was
necessary.
Maximum stresses from Dr. Edward L.
Wilson's report were utilized by the
Department to perform a reinforced-
concrete-theory analysis of the structure,
which resulted in the tensile stresses
shown in Figures 184 through 186. These
are peak instantaneous stresses with the
occurrence time shown at the bottom of
each figure. The largest concrete ten-
sile stress of any concern is 2172 kPa
(315 psi) . It was obtained in an area
of the piers where the reinforcing steel
available is almost negligible (Figure
185, Elevation 850, Station 12+68).
However, experimental research and pro-
totype observation have shown— that
the dynamic tensile strength of mass
concrete is at least 10 percent of its
static compressive strength or, in this
instance, 3792 kPa (550 psi); therefore,
the peak stress of 2172 kPa (315 psi)
at the downstream end of the piers is
well within the tensile strength of the
concrete.
Maximum concrete tensile-stress values
1/ Refer to text and references of Chapter VII ("Earthquake Response Analysis of
Thermalito Diversion Dam" by Anil K. Chopra) .
291
292
293
values shown in Figure 184 are not con-
sidered critical, because the rein-
forcing steel available in that area is
capable of resisting the total earth-
quake tensile force without any contri-
bution from the surrounding concrete
(see Figure 186) .
Although piers 1 and 10 were not investi-
gated numerically by the Department,
they are not expected to develop critical
stresses because they carry half as much
load as do the adjacent piers, and a
significant portion of their height is
in direct contact with the rock abutment.
The Department also investigated the
structure for stability against sliding
through the shear-friction equation
Q =
CA + N tan 0.
H
The use of a
cohesion value of 3447 kPa (500 psi)
produced a shear-friction factor of 11.6,
which is ample against sliding.
Conclusion
The investigations performed indicate
that when the Oroville Flood Control
Outlet Structure is subjected to the
Reanalysis Earthquake ground motion^ it
is stable, and that expected compressive
and tensile stresses are within the allow
able limits established for the structure
Introduction to Figures 184 through 186
1. Smaller tensile stresses and com-
pressive stresses were intentionally
left out due to their uncritical
magnitudes.
2. Although stresses in piers 5 and 6
are somewhat different from those in
piers 2, 3, 4, 7, 8 and 9, the small
variation did not justify showing
them independentaly.
3. Figures 184 through 186 show the j
elevation of a pier with an element
mesh layout. Actual stresses are
tabulated inside the elements.
294
920.17
Maximum Tensile Stresses m
Piers 2 thru 9 at time 7.76 sec.
Top- Reinforcing Steel Stress ( psi )
Bot- Concrete Stress ( psi )
Figure IS'*. Maximum Tensile Stresses at Time 7.76 Seconds
295
920.17, g
1 5
14
13
|\\\\^
:\
m\\\\V
\\\\\\\\\
1 \ \ \ \ \ \ \ff''A''^A
884.00 1^
1 \ \ \ \ \ \ \127\178\
1 \ \ \ \ \ \s54\7ao\7ao\
\ \ \\ \ \ \l24\l4 8\l4 8\
1 \ \ \ \ 5Jj\ *jj\ 765\ eaiK 92B\I0
V
r 868.75, ^j
\ \ \\ \ \ \ \\ M02
1 \ \ \ \lOI \ I20\l45\l67\l 76 >\
1 \ \ \ \s9l\7Zi\^B75\l044\lZ 13
\
9
\^
-~a \ \ \ll2\l37\l66\l98\5?^
O 8
\ \ \ \ 627\ 77s\ 92b\/I8I
\ \
f_ 856.99
<
>
\H
Jl \ \n9\.47\,7e\22\^!3^
\
^^ \ \ SeA 775\ 960\,207\''"
UJ
--^ \ \ \ \ \ \ \ \
-1 846.17 6
\
-~J
L-_____\ \I07 \ I47\ I82\22 9\ 3I5\
UJ
\
517
733
923
1128
1265
939
^
^^
^—
98
1 39
1 75
2 14
240
1 78
5
6 70
854
1029
1/18
970
538
-^
' ^^
■
127
162
195
2 1 2
1 84
102
'
4
622
1 1 8
012
1 54
970
1 84
1060
20 1
loia
1 93
838
159
5 75
765
923
1007
1028
1028
120
82 1.79
2
8 13.60
1 09
1 45
1 75
1 9 1
1 95
1 94
22<
"X46I
2X7
533
1 0 1
72 2
1 37
865
1 64
95 4
1 8 1
99 1
188
1070
203
<2ie
231
511
97
701
1 33
838
159
928
1 76
986
1 87
1081
1165
9?l
/09\
?nft\
1
5 14 13 1211 10 9 8 7 6
5 4 3 2 1
o
o
+
a
1
p
v>
Maximum Tensile Stresses in c
Piers 2 thru 9 at time 8.46 sec. ^
0
Top- Reinforcing Steel Stress (psi )
Bot- Concrete Stress (psi)
Figure I85. Maximum Tensile Stresses at Time 8.^6 S
econds
296
920.17
Maximum Tensile Stresses (ksi) in
Piers 2 thru 9 in reinf. steel at
time 7.76 sees, disregarding
contribution from concrete
Figure 186. Maximum Tensile Stresses at Time 7-76 Seconds in Steel
297
A REPORT TO THE
DEPARTMENT OF WATER RESOURCES
STATE OF CALIFORNIA
on the
Earthquake Analysis of the Oroville Dam
Flood Control Outlet Structure
by
Edward L. Wilson
Professor of Civil Engineering
University of California, Berkeley
Frederick E. Peterson, President
Engineering/Analysis Corporation
Berkeley, California
Ashraf Habibullah, President
Computers/Structures International
Oakland, California
June 1977
299
TABLE OF CONTENTS
PAGE
I. Introduction 1
A. Background 1
B. Basic Assumptions 1
II. Three-Dimensional Analysis Without Hydrodynami c Interaction . 3
A. Objective and Scope 3
B. Analysis Procedure 6
1. Idealization 6
2. Analysis process 6
3. Output of results 8
C. Structural Model 8
1. Finite element mesh 8
2. Material properties 9
3. Displacement boundary conditions 9
4. Mass distribution 9
D. Analysis Cases and Results 9
1. Static Analysis 9
a. applied loads 13
b. results 15
2. Analysis for mode shapes and frequencies 22
3. Response spectrum analysis 22
4. Time history response analysis 29
a. solution parameters 29
b. results 31
III. Two-Dimensional Analysis With Hydrodynamic Interaction ... 44
A. Analysis Without Interaction 44
B. Analysis With Interaction 44
C. Extension to Three Dimensional Analysis 46
IV. Transverse Earthquake Analysis 47
V. Vertical Earthquake Analysis 48
VI. Final Remarks 49
300
I. INTRODUCTION
A. Background
The analysis presented in this report was conducted under a consult-
ing agreement between the Department of Water Resources of the State of
California and E. L. Wilson. The analysis was monitored by personnel of
the Division of Design and Construction.
The purpose of the report is to present an Earthquake Analysis of the
Oroville Dam Flood Control Outlet Structure utilizing the finite element
method and dynamic techniques suitable for this particular structure. It
is not the objective of this report to assess the structural safety of the
structure but to present the results (stresses and displacements)of a
specific analyses based on the given loadings and stated assumptions.
B. Basic Assumptions
The structure to be analyzed is a complex three dimensional structure
given in detail in drawings A-3B5-1 to A-3B5-7 which were supplied by
Department of Water Resources. Since the three dimensional dynamic
analysis of the complete series of monoliths is beyond the present state-
of-the-art with respect to computer capabilites it was necessary to study
the three dimensional dynamic behavior of a typical monolith only. For
elastic behavior this idealization should introduce only minor errors--
less than 10 percent.
The specified earthquake loading produces stresses and displacements
which must be combined with the results of other load conditions if the
total state of stress is to be evaluated. In order for the results of the
various load conditions to be combined in a rational manner dead loads
and static hydrostatic loads were applied to the same three dimensional
finite element model and are presented in this report as separate results.
301
2
Also, the upstream-downstream direction was assumed to be the
critical direction with respect to the dynamic earthquake loading. A
separate simplified analysis is presented to evaluate the significance
of the earthquake loading in the transverse direction. In addition,
potential vertical earthquake stresses must be considered separately.
At the present time an exact three dimensional analysis of a dam-
reservoir system is not possible. Therefore, it was necessary to estimate
this effect by examining this effect on a two-dimensional structure with
similar dynamic properties.
Only linearly elastic behavior was considered. After the results
from the various analysis are combined it will be necessary to apply
experience and engineering judgment in order to estimate the significance
of nonlinear behavior and to estimate the realistic behavior of the
structure under the specified earthquake.
302
II. THREE DIMENSIONAL ANALYSIS WITHOUT HYDRODYNAMIC INTERACTION
A. Objective and Scope
This section describes the three dimensional static and dynamic
analysis of a typical section of the mass concrete spillway structure.
The objective of the analysis is to compute stresses in the concrete due
to seismic excitation.
A critical exposure condition for the spillway structure occurs when
seismic input acts parallel to the direction of flow. For this case,
horizontal motion is induced in the breast wall which must be resisted
by overturning (i.e., vertical stresses) in the piers. From the propor-
tions of the structure, it is reasonable to approximate the horizontal
translation of the foundation as a rigid body; i.e., at any instant, the
acceleration at the base of all piers is identical. The ends of the
spillway structure terminate in substantial embankments; thus, it is
reasonable to neglect horizontal motion transverse to the direction of
flow for an earthquake acting in the direction of flow.
A typical section of the spillway structure is bounded between two
vertical planes as shown schematically in Figure II. 1. One plane bisects
the pier and the other coincides with a mid-plane of the breast wall.
The X, Y, Z reference system shown in the figure is chosen as follows.
X is horizontal and transverse to the direction of flow. Y is vertical
and directed up. Z is horizontal, parallel to flow and directed upstream.
A plan view of this same section is shown in Figure II. 2. Assuming that
the X-translation is zero on both vertical planes and that the same Z-
direction ground input acts at the base of all piers, an analysis of the
section shown in Figure II.l will predict a response typical of that for
the entire structure.
303
FIGURE II. 1 OROVILLE SPILLWAY STRUCTURE
SCHEMATIC OF TYPICAL SECTION
304
>x
u w
305
B. Analysis Procedure
The purpose of the analysis is to predict seismic stresses in the
concrete structure. For comparison, static stresses under operating
conditions are also calculated.
1 . Idealization
The typical section isolated in Figure II. 1 is idealized as a three
dimensional elastic continuum. The structure considered is the mass
concrete only. Non-structural masses are lumped at various locations in
the structure; e.g., the gate mass is lumped at the trunnion. Added mass
due to structure/reservoir interaction is not considered in the three
dimensional analysis.
An elevation view of a typical section is shown in Figure II. 3.
Ground acceleration is applied through the base of the pier and is
directed in the global Z-direction. The structure is free to deform in
the Y,Z plane, but is restrained against displacement normal to the
vertical planes: X = 0 ( pier) and X = 11.292' ( breast wall).
2. Analysis Process
The three dimensional stress analysis was performed using the linear
elastic finite element computer code known as EASE2. Usage and theoretical
basis for EASE2 are described in the reports:
(1) "EAC/EASE2 - Elastic Analysis for Structural
Engineering", User Information Manual,
Control Data Corporation, Cybernet Services,
Publication No. 84002700, Revision B (6-15-76).
(2) "EAC/EASE2 - Dynamic Analysis for Structural
Engineering", User Information Manual,
Control Data Corporation, Cybernet Services,
Publication No. 84000040, Revision A
(6-15-76).
The EASE2 analysis was performed in the sequence outlined below:
(1) prepare a finite element mesh consisting
of the three dimensional, eight-node solid
elements;
306
\^<^)(b.e>a' h»—
i(h.i^'
&Ge>.ib'
3\^.(bO'
&\\.e>o'
FIGURE II. 3 OROVILLE SPILLWAY STRUCTURE
ELEVATION OF TYPICAL SECTION
307
(2) lump non-structural masses at corresponding
locations in the model;
(3) calculate static loads due to gravity,
hydrostatic pressure and trunion prestress
and analyze the structure for operating
condition static stresses;
(4) analyze the structure for mode shapes and
frequencies;
(5) knowing the structure frequencies, calculate
the spectral response due to the earthquake
time history (modified Pacoima and Taft, 20
seconds duration);
(6) to locate regions of critical stress, perform
a response spectrum analysis of the structure
assuming Z-direction input at the base of
the pier;
(7) requesting output at locations of high
stress, calculate the dynamic response of
the structure due to Z-direction ground
input acting at the base of the pier.
3. Output of Results
Complete output from a three dimensional time history analysis is
enormous. To reduce print-out to manageable proportion, it is necessary
to limit output to those quantities of primary concern. For the spillway
structure, this primary quantity is principal tension in the concrete.
The static and response spectrum analyses produce complete spatial
distributions of stress and thus can be used to locate regions of high
stress. Output from the seismic response analysis is limited to principal
tension plotted versus time, one plot for each location of potentially
critical stress. From the plots, the times at which maximum stresses
occur can be determined. Finally, complete distributions of principal
tension are displayed at those times at which maxima were found to occur.
C. Structural Model
1. Finite Element Mesh
308
The section of Figure II.l is modeled with 285 eight-node solid
elements. The mesh is built up of four vertical layers of elements as
shown in Figure 11,4, Figure 11,5 plots the +X face of elements l-to-177
which represent the pier, and Figure II. 6 is an enlargement of one of the
three breast wall element layers.
2, Material Properties
The modulus of elasticity and Poisson's ratio of the concrete are
taken as 5000 ksi and 0,2, respectively. The weight density of the
concrete is 160 pcf.
3, Displacement Boundary Conditions
The base of the pier is fixed. Transverse X-displacement is zero
for all nodes in the pier mid-plane and breast wall mid-plane. These
boundary conditons allow free Y,Z translation of the structure at all
nodes above the base, and X- translation is free at all nodes except
those on the vertical boundary planes,
4, Mass Distribution
The total mass of the structure model is the sum of the mass due
to element volume (i.e,, structural mass) plus non-structural added mass.
The total mass due to element volume was computed by EASE2 as 3906 ,
This is 6% lower than the working drawing estimate of 4153 (corrected
to 160 pcf concrete). The total non-structural mass is 337 , Each non-
structural mass item (e.g., inspection walkway, maintenance deck, etc.)
has its mass distributed to the node or line of nodes nearest its actual
location in the structure.
D. Analysis Cases and Results
1 . Static Analysis
Three static loading conditions:
309
I
/state: of CRLIFORNIfi/DEPRRTMEHT OF HRTER RFSOURCES/OROV ILLE ORM SFILLWRY/
/STRTIC AND OrtlRMIC THREE DldENSlONRL FINITE ELEtlENT RNRLYSIS/
ISOMETRIC VIEW OF TOTRL MODEL -- NODE AND ELEMENT NUMBERS SUPPRESSED
EflC/CSI/ERSEZ/E2FL0r
VIEW NUMBER I
FRAME NUMBER 1
RUN DATE lO/M/76
FIGURE II. 4 OROVILLE SPILLWAY STRUCTURE
3/D FINITE ELEMENT MODEL
310
I
n
/STRTE OF CRLIFORNIR/DEFRRTMENT OF WPTER RESOURCES/OROV ILLE DRM SPILLWAY/
/STRTIC AND OYNRtllC THREE DIMENSIONAL FINITE ELEMENT RNRLYSIS/
/PROJECTION OF THE STRUCTURf ON THE Y-Z PLANE/
EAC/CS1/EASE2/EZPL0T
VIEW NUMBER Z
FRAME NUMBER 1
RUN DATE 10/15/76
FIGURE II. 5
OROVILLE SPILLWAY STRUCTURE
PIER ELEMENT LAYER
311
/SfRTE OF CRLlFORNlfl/OEFRRrnENT OF HRTER RESOURCES/OROV [LLE ORH SFILLHRY/
/STATIC RNO OTNRfllC THREE DIMENSIONRL FINITE ELEMENT RNBLYSIS/
/LRTER OF ELEMENTS BETHEEN i=4 AND IrS/
ERC/CSI/EPSE2/E2FL0T
VI EH NUMBER I
FRPME NUMBER Z
FIGURE II. 6
OROVILLE SPILLWAY STRUCTURE
BREAST WALL ELEMENT LAYER
312
T3
(1) gravity;
(2) hydrostatic pressure (closed gate, water surface elevation
of 900 feet);
(3) trunnion anchorage prestress
are analyzed individually and in combination. The combined loading case
is called the "operating condition",
a. Applied Loads
Gravity loading is a 1-g static acceleration applied in the minus
k k
Y-direction. The total gravity loading is 4243 ; this includes 3906
due to structure plus 337 due to non-structural mass items.
Hydrostatic loads are computed assuming that the water surface is
at an elevation of 900.00 feet. The loading is separated into two major
parts:
(1) pressure on the exposed surface of the mass concrete structure;
and,
(2) pressure on the radial gate.
The structure is loaded by applying pressure normal to the face of all
exposed solid elements. Integrating the pressure distribution applied
on the finite element model, we obtain a total horizontal force of 1377
(-Z) and a total vertical force of 752*^ (+Y); see Figure II. 7. Actual
uplift acting on the elliptical underside of the breast wall was calculated
as 757 . The horizontal and vertical resultants due to hydrostatic
pressure on the gate are 1296'^ (-Z) and SSo"^ (+Y), respectively. These
forces act on the pier at the trunnion.
A self-equilibrating load set simulating trunnion anchorage prestress
was applied to the pier to offset the hydrostatic gate load. Twenty four
(24) tendons (in 1/2 of the pier) at 142.6'^ per tendon results in a total
prestress force of 3422 . The line of action of the opposing prestress
forces was aligned through the average trajectory of the tendon array.
313
'i^OO. OO -^^- /
1^77'<
e>\^.(2>o'
nb
^K^\f\V. (SAte
FIGURE II. 7 HYDROSTATIC LOAD RESULTANTS
314
15
b. Results
Static analysis results are described in this section. Stresses due
to gravity alone and stresses for the operating condition (i.e., gravity
+ hydrostatic + prestress) are presented.
The spatial distribution of stress in the concrete is displayed as
follows. A Y,Z projection of the 177 solid elements used to model the
pier is shown in Figure 11.8(A). Figure 11.8(B) is an elevation view
of the same 177 elements transformed to an integer coordinate system in
which all element faces have the same area. If element centroidal
stresses were printed at their respective physical (Y,Z) locations, the
result would be unreadable. Values printed in the integer system (Figure
11.8(B)) form a regular array as maybe seen in Table II. 1. This table
lists the vertical (Y) stress in psi calculated in each pier element for
the gravity loading condition; negative values indicate compression.
Maximum vertical compression is 300 psi in element 14 which is located
in the heel of the pier. Tables II. 2 and II. 3 are distribtuions of
minimum and maximum principal stress, respectively, due to gravity only.
Note that the vertical and minimum principal stresses in the vacinity
of the heel are nearly the same; this indicates that the minimum stress
is approximately vertical in the heel region. Stresses in the breast
wall due to gravity are low; the min/max principal stresses fall in the
range -100 psi/10 psi.
The principal stresses for the operating condition (sum of all
static loads) are shown in Tables II. 4 and II. 5. One notes that principal
stresses are not an exact sum at the principal stresses due to the indi-
vidual load conditions; since theirdirections are not the same. However;
near the heel where all load conditions tend to produce vertical stresses
315
— t
— 1
— \
1
1
t 1
— \ — \- -i — \ — 1 — ^-^y
\
'
-
'\
x'
^
s
\
\
V
\
\
N,
.N
n"'
^
\
\
^
N
X
X
N
N
\
\
N
\
W Eh
S B ca
M H X
H CO
> o
Eh U
Z Z El
O M <
H Z
Eh D M
!?:«9
J rt o
HSU
W E
W Eh
< M
> to
M X
►J K
U 0.
316
17
HEADING LINE THREE
STATIC LOAD CASE NUMBER
ELEMENT DISPLAY SET NUMBER
SCALE FACTOR
OUTPUT STRESS COMPONENT
GRAVITY LOADS / VERTICAL STRESS / PSI UNITS
II
l>
.IO00E*04)
2)
OROVILLE DAM SPILLWAY/ HALF OF TYPICAL BAY/ STATIC ANALYSIS RESULTS/
PIER ELEVATION VIEW/ ELEMENTS O0I-TO-IT7/
GRAVITY LOADS / VERTICAL STRESS / PSI 'UNITS
SOLID ELEMENT CENTROIOAL STRESSES
-n
-13
-12
-12
-12
-11
-11
-10
-9
-8
-16
-16
-16
-18
-20
-18
-17
-14
-12
-9
-21
-22
-22
-23
-26
-24
-21
-17
-13
-9
-27
-27
-28
-30
-32
-29
-26
-21
-15
-5
-32
-32
-33
-36
-42
-40
-36
-30
-21
-7
-25
-39
-38
-38
-40
-47
-46
-43
-36
-23
-19
-3
-*9
-47
-44
-45
-54
-56
-52
-40
-27
16
-53
2
-8
-69
-67
-58
-55
-67
-71
-59
-43
-20
-14
-41
-126
-134
-117
-100
-90
-81
-62
-41
-23
22
-46
-226
-239
-217
-174
-122
-88
-66
-45
-18
2
-1
-13
-48
-244
-236
-215
-180
-138
-101
-74
-50
-27
-9
-6
-20
-36
-25A
-240
-216
-184
-147
-112
-83
-58
-36
-21
•16
-22
-26
-265
-247
-219
-188
-154
-120
-91
-66
-45
-32
-26
-23
-23
-281
-252
-219
-190
-159
-127
-98
-74
-54
-41
-33
-27
-18 -13
-300
-246
-219
-191
-162
-131
-104
-80
-61
-48
-39
-30
-22 -10
TABLE II. 1
STATIC GRAVITY STRESSES
VERTICAL (Y) COMPONENT
317
HEADING LINE THREE
STATIC LOAD CASE NUMBER
ELEMENT DISPLAY SET NUMBER
SCALE FACTOR
OUTPUT STRESS COMPONENT
= <6RAvnY LOADS / MINIMUM PRINCIPAL STRESS / PS| UNITS
= ( 1)
= ( 1)
= < .1000E*0<i)
= < 7)
OROVILLE DAM SPILLWAY/ HALF OF TYPICAL BAY/ STATIC ANALYSIS RESULTS/
PIER ELEVATION VIEW/ ELEMENTS OOI-TO-177/
ORAVITY LOADS / MINIMUM PRINCIPAL STRESS / PSI UNITS
SOLID ELEMENT CENTROIOAL STRESSES
-1«
-13
-13
-13
-13
-12
•11
-10
-10
-10
-16
-16
-17
-19
-21
-19
-17
-14
-12
-11
-21
-22
-22
-24
-27
-24
-21
-18
-13
-10
-27
-27
-28
-30
-33
-30
-26
-22
-15
-5
-32
-32
-33
-36
-43
-40
-37
-31
-22
-12
-32
-39
-38
-38
-40
-48
-47
-44
-37
-28
-26
-9
-49
-47
-44
-45
-54
-57
-53
-43
-31
7
-59
-12
-10
-70
-68
-59
-56
-67
-71
-61
-4 7
-29
-28
-42
-129
-137
-121
-102
-91
-81
-63
-44
-27
-2
-46
-227
-240
-219
-178
-124
-88
-66
-46
-18
-4
-4
-13
-50
-2*4
-236
-215
-181
-139
-101
-74
-51
-27
-13
-15
-27
-36
-254
-240
-216
-184
-148
-112
-83
-58
-36
-23
-24
-27
-27
-265
-247
-219
-188
-154
-121
-91
-66
-45
-32
-29
-26
-23
-281
-253
-219
-190
-159
-127
-99
-74
-54
-41
-34
-27
-18 -13
-304
-247
-220
-192
-163
-133
-105
-81
-62
-48
-39
-30
-22 -10
TABLE II. 2
STATIC GRAVITY STRESSES
MINIMUM PRINCIPAL COMPONENT
318
19
HEADING LINE THREE
STATIC LOAD CASE NUMBER
ELEMENT DISPLAY SET NUMBER
SCALE FACTOR
OUTPUT STRESS COMPONENT
6RAVITY LOADS / MAXIMUM PRINCIPAL STRESS / PSI UNITS
1)
I)
.1000E*04>
9»
OROVILLE DAM SPILLWAY/ HALF OF TYPICAL BAY/ STATIC ANALYSIS RESULTS/
PIER ELEVATION VIEW/ ELEMENTS 00I-TO-I77/
GRAVITY LOADS / MAXIMUM PRINCIPAL STRESS / PSI UNITS
SOLID ELEMENT CENTROIOAL STRESSES
0
0
0
1
2
0
0
0
0
0
0
1
3
5
4
2
1
0
0
1
2
4
9
7
6
4
0
0
1
2
5
11
11
10
9
5
0
1
2
5
13
12
12
11
8
1
0
0
1
13
14
15
14
16
20
12
0
0
0
11
14
15
16
15
23
I
9
7
3
5
5
6
9
11
15
23
23
-2
-6
-8
-10
-4
0
0
5
12
21
50
1
6
-4
-10
-14
-4
1
0
4
13
27
30
14
5
3
5
5
1
0
0
0
4
10
6
0
2
0
0
0
0
0
0
0
0
2
1
0
-I
-I
-I
-1
0
0
0
0
0
0
0
5
3
4
3
2
2
2
1
1
1
1
0
33
-27
-24
-20
-17
-14
-11
-8
-7
-5
-4
-3
-2
-1
TABLE II. 3 STATIC GRAVITY STRESSES
MAXIMUM PRINCIPAL COMPONENT
319
20
■jr/inpir. LINF THPCr = (r,R4VlTYtHrOPOSTaTrC»PRF5TRESS^ MTNIMUM PPINCIPAL STRESS/ PSI UNIS
STflTTC unnn rtsr fUnpFR = ( u)
nP->VTLLt: nan '-.r-TLLWAY/ HALF OF TYPICAL BAV^ STATIC ANALYSIS PFSULTS/
PT€R EL'^"ATTOK' VIFVI/ FLE1FNTS fOl-Ta-177/
'■."AVITYvHYIDTSTATI'-trrrsTRESS/ MIMI1U" ^RTNCI^aL STR'SS/ PSI UMITS
soLTn ^L'^''ENT rF^'■^P0I^aL stresses
= (
1)
: (
. 1 'Or- to<»)
= (
7)
-1'
-1'
-12
-1?
-13
-12
-12
-11
-IG
-8
-lu
-It;
-17
-iq
-2]
-2'
-18
-15
-12
-10
-2?
-??
-2'
-21.
-27
-21.
-21
-18
-15
-11
-T'
-20
-?7
-2"
-3u
-c7
-25
-23
-IQ
-1.3
_T(S
-■»T
-31
-32
-?(S
-»7
-38
-35
-■'u
-15
-33
-UT
-37
-36
-37
-I.?
-1*7
-1.8
-i»6
-36
-31.
-23
-U6
-1*2
-1.1
-liU
-57
-62
-61.
-6 1
-53
-21
-1.3
-18
-11
-=56
-51
-U7
-5f^
-8Q
-83
-9!.
-8 2
-72
-67
-ifS
-1?
-« "
-72
-Pf,
-11"
-1C3
-99
-1)2
-11.2
-iro
-t.9
129
-121.
-I2r
-123
-13r
-115
-107
-135
-265
-168
-131
-27
-55
12'
-IIU
-lit
-IL 5
-in/
-135
-11.7
-21"
-?C2
-2?"
-150
-57
-21.
11'^
-ll-'
-IIF
-113
-95
-161
-?d9
-217
-237
-165
-l-'7
-75
-31
-■^7
-116
-127
-IZIS
-122
-12?
-297
-21.8
-12j
-11.8
-13^
-go
-71.
-•f"
-12?
-l?o
-I'll
-l(»tt
-139
-196
-19 8
-15-'
-153
-139
-112
-91.
-96
-r^
-12-'
-xu;
-15-7
-156
-146
-11'-'
-l-^l
-190
-165
-11.6
-12P
-103
-81.
TABLE II. 4 STATIC OPERATING CONDITION STRESSES
MINIMUM PRINCIPAL COMPONENT
320
21
HF/\nTNr, LTME THOFF
"STATIC LO/vn cftS? NDMnF"^
■^L^'I^NT niSPLAV SFT NUM3FR
SCAL"^ FHCT03
lOUTPUT ^TC'T^^; r^^'F'^NFHT
GPflVTTY+HYDrnSTnTTC*PPFSTRFSS/ MAXIMUM PRINCIPAL ST'FSS/ PSI UNITS
1.)
1)
. 1 C 0 ? c ♦ 1 1. )
9)
OPO'iTLl-E HAM <^PILLMAY/ HALF OF TYPICAL "AY/ STATIC ANALYSIS PFSIJLTS/
"1'"° ELEVATION vii^W/ FLEMFt'Tt^ jiJt-TO-177/
GRAVIT YmYnPOSTaiTC+PPESTPrSS/ maximum POTN^I^AL stress/ PST UNITS
SOLin ^LE^^'NT CEMTpnirflL S''=!ESSES
?
T
1
1
T
1
1
-
3
0
T
"
C
1
7
1
1
n
0
0
-2
_?
-2
-2
-1
-
0
n
r
0
-5
-5
-^
-5
-3
1
n
J
Q
0
-7
-7
-6
-fi
-I4
1
0
p
c
1
-1
-9
-n
-6
-f>
-1.
1
0
-
c
-2
1
-q
-1
-6
-7
-5
1
3
3
u
21
1
7
19
_ 7
_ n
. ■»
-f>
-6
2
D
1
0
-i»
- 3
-9
-q
-u
-11
-10
3
"
•y
• 7
uq
<t
-^
-9
-5
-7
-6
2
0
1*
-9
-6
52
17
12
^
1
2
1
0
u
-f>
6
-12
2i»
-5
2
-1
"
7
12
1"
19
-7
7
-'
5
n
1
2
-1
ti
??
I4:
75
?li*
-?7
-■5
3
-1
0
-1
-1
IT
3LI
■55
12-<
Z<^'
205
3
t;
u
3
2
3
1
77
lU
2?
1.6
155
221
!!♦•"
IS
-1?-
-15
-13
-9
-6
- 3
TABLE II. 5
STATIC OPERATING CONDITION STRESSES
MAXIMUM PRINCIPAL COMPONENT
321
22
a direct summation is a good approximation. Also, the stresses in the
breast wall for this combined load case are in the range -100 psi to 10
psi.
2. Analysis for Mode Shapes and Frequencies
The ten (10) lowest natural frequencies and mode shapes were determined
using EASE2. Table II. 6 lists the first five (5) frequencies and their
associated global (X,Y,Z) mass modal participation factors. By definition,
the X-direction mass modal participation factor for the i-th mode is:
ij;^ = (t)T M I
^x ^1 = -X
where ^. is the i-th mode eigenvector, M is the system mass matrix and
I is a vector containing ones at X translational degrees of freedom
and zeroes elsewhere. If \pl is small (in comparison to ip^ and i|jM , it
X y z
means that the i-th mode has practically no X component. From Table II. 6
it is seen that the ^ are negligible from which we conclude that the
mode shapes are essentially two-dimentional in the vertical Y,Z plane.
Figures II. 9, 11.10 and 11,11 plot eigenvectors for modes 1, 2 and 3
respectively. The undeformed structure is shown dashed in these plots.
The second mode represents localized vibrations in the bent which supports
the road bridge. Generally, however, the modes are combinations of shear
and flexure involving the entire pier. The breast wall responds essentially
as a rigid mass atop the pier cantilever.
3. Response Spectrum Analysis
The "modified Pacoima and Taft" acceleration time history (shown for
20 seconds in Figure 11.12) is assumed to act at the base of the pier in
the global Z-direction. The response spectrum for 5% damping for the
modified Pacoima and Taft is plotted in Figure 11.13. Note that the
spectral acceleration approaches the peak acceleration (0.6g) at the high
frequency end.
322
23
MODE
NUMBER,
i
NATURAL
FREQUENCY ,
MASS MODAL PARTICIPATION FACTORS
^x
4
*l
1
10.07 hz
.0005
0.7057
2.4645
2
22.60 hz
-.0028
0.8632
0.1599
3
24.84 hz
-.0058
2.0934
1.5704
4
28.14 hz
-.0073
1.6520
-0.7618
5
36.39 hz
-.0067
-0.0664
0.2202
TABLE II. 6 OROVILLE SPILLWAY STRUCTURE
NATURAL FREQUENCIES AND ASSOCIATED
MASS MODAL PARTICIPATION FACTORS
FOR THE LOWEST FIVE MODES
323
24
vKvTx \ \ \ \ \ \ "^
\AXi\--^rr\\\ \ \ ^ ^
u\\\ \\\\\\\ ^
\ WWi^^vWVxv^ ^
mvM \ \\\-\-^Va^ - - .
Ur4r-V\\ \ \ \ \ V\ \1
\ \'\1\-V-V^
Nr\\vv~" "^^^
T- 1
fc^X-.-^
VT\\\\, \
1
r^trtTirTi lzl
(
1
+
i
WVTT^^
1
+-
f Jrr ^ 1 1
1
UI
, n
\
F ]
1 [
K
r\
/STqiE OF CRLIFORNIP/DEPPRTMENT OF URTER RES0URCE5/0R0V ILLE DfiM SPILLUflV/
/STRTIC RNO OYNRMIC THREE DIMENSIOHPL FINITE ELEMEHT RNRLYStS/
/PROJECTION OF THE STRUCTURE ON THE Y-Z PLRNE/
z, — 1
EBC/CSI/ERSE2/E2PL0T
VIEU NUMBER 1
FRAME NUMBER 1
RUN DOTE 10/30/76
FIGURE 11,9 OROVILLE SPILLWAY STRUCTURE
PLOT OF MODE SHAPE NUMBER ONE
324
25
/STRTE OF COLIFGRNIfi/OEFflRTMENT OF URTER RESOURCES/OROV I LLE DflM SPILLURY/
/STRTIC AND DYNAMIC THREE OIMEHSIONRL FINITE ELEMENT RNRLYSIS/
/PROJECTION OF THE STRUCTURE ON THE Y-Z PLANE/
EAC/CSI/EASE2/E2PL0T
VIEU NUMBER 1
FRAME NUMBER 2
RUN ORTE 10/30/76
FIGURE 11,10 OROVILLE SPILLWAY STRUCTURE
PLOT OF MODE SHAPE NUMBER TWO
325
26
/STRTE OF CfiLIFORNin/DEPflRTMENT OF UfiTER RE50URCES/0R0V I LLE DRM SPILLUfir/
/SrfiTlC fIND UYNRMIC THREE DIMENSIONRL FINITE ELEMENT RNRLYSIS/
/PROJECTION OF THE STRUCTURE ON THE Y-7 PLRNE/
EflC/CSI/ERSE2/E2PL0T
VIED NUMBER 1
FRAME NUMBER 3
RUN DATE 10/30/76
FIGURE 11.11
OROVILLE SPILLWAY STRUCTURE
PLOT OF MODE SHAPE NUMBER THREE
326
27
o
h
x
R
o
^
H
H
U)
H
P
K
§
W
a
p£
H
j>i
R
H
o
s
c;
O <
H
CM
H
^
W
H
h-1
h
W
H
CJ
O
u
f^
< s
1 30DN
/lldOti 99b/
NOliHnSNbdi-
3—78786
327
/ST9TE OF CRLIFORNIfl/DEFRRTMENT OF UHTER RESOURCES/OROV ILLE OfiM SPILLURT/
/STATIC AND DTNflMIC THREE DIMENSIONAL FINITE ELEMENT ANALYSIS/
1-
I- 0.90
X-TRANSLRTION
/ABS ACCEL/
NODE 1
FREQUENCY (CYCLES/UNIT TIME)
FIGURE 11,13
RESPONSE SPECTRUM (5% DAMPING) FOR
MODIFIED PACOIMA AND TAFT
328
29
A response spectrum analysis using a square root of the sum of the
squares combination of the lowest ten modes was perfomred with EASE2.
Vertical (Y) stresses in the pier due to Z-direction base input are
listed in Table II. 7. Mote that the critically stressed region is the
pier heel; 457 psi is predicted in element 14 at the base. Stresses in
the breast wall are considerably lower than those predicted in the pier.
The maximum X-direction stress in the wall occurs at the crest and is
estimated to be 32 psi .
The maximum component of deflection calculated by EASE2 is 0.136
inch (Z) at the crest. A hand estimate of the crest displacement shows
that the first mode contributes over 95%; this means that the structure
is responding primarily in its first mode.
4. Time History Response Analysis
From the response spectrum analysis we note the following:
(1) the first mode is the principal contributor to the response
of the structure;
(2) stresses are largest in the pier heel region but are also
significant in the vacinity of the pier toe;
(3) the pier provides horizontal support to an essentially rigid,
massive breast wall; stresses in the breast wall are low
because it responds nearly rigidly.
The essential characteristics of the time history analysis can be
inferred from the results of the response spectrum solution. The results
of both analyses should be practically identical because the principal
contribution to overall response is contained in the lowest modes,
particularly the first mode.
a. solution parameters
The forcing function is applied as Z-direction ground input acting
at the base of the pier. The same "modified Pacoima and Taft" accelera-
tion history used for the response spectrum analysis (Figure 11.12) is
329
HEADING LINE THREE
RESPONSE CASE NUMBER
ELEMENT DISPLAY SET NUMBER
SCALE FACTOR
OUTPUT STRESS COMPONENT
= (VERTICAL (Y-DIRECTION) STRESS/ PSI UNITS/
= ( 1)
= ( II
= ( .lOOOE^O'.l
= (
2)
OROVILLE DAM SPILLWAY/ HALF OF TYPICAL BAY/ RESPONSE SPECTRUM ANALYSIS/
PIER ELEVATION VIEW/ ELEMENTS OOl-TO-177/
VERTICAL (Y-OIRECTION) STRESS/ PSI UNITS/
SOLID ELEMENT CENTROIOAL STRESSES
29
24
21
18
14
10
6
4
7
17
27
25
23
25
26
17
8
10
25
47
36
32
30
29
32
18
7
22
47
76
*6
39
33
32
34
17
12
35
62
108
5<*
44
35
32
36
16
19
47
84
84
50
62
48
37
32
37
14
26
61
85
111
188
72
57
42
33
38
15
33
65
107
179
25
6
14
96
80
56
38
40
16
41
82
141
210
23
164
155
107
59
38
21
58
108
155
205
24
293
277
199
108
42
26
69
115
156
161
82
6
29
327
278
206
125
55
27
68
112
147
153
113
63
30
SS*.
289
212
134
63
27
66
108
137
143
128
114
84
385
303
216
138
68
27
63
102
128
137
135
143
200
421
310
215
139
71
28
59
96
121
133
138
161
192 211
457
299
214
139
73
28
55
91
116
130
143
166
183 162
TABLE II. 7
RESPONSE SPECTRUM ANALYSIS STRESSES
VERTICAL (Y) COMPONENT
330
31
also used in the time history response analysis. The structure is subjected
to ground motion for the full 20 second duration.
Even though the response is principally represented by the first mode,
contributions for all ten (10) of the structure's lowest modes are included
in the transient response analysis. Five (5) percent damping is assumed
uniformly for all modes. The time interval at which output is displayed
is limited to 1/5 of the period of the first mode or 0.02 second (i.e.,
20% of 1/10.07 hertz). Since the excitation is applied for 20 seconds,
output is produced at 1000 time points. Using the predictions from the
response spectrum analysis, the amount of time history output can be
narrowed considerably; i.e., principal stresses in the pier are of major
concern, and output is limited to these stress versus time histories.
Complete spatial distributions of principal stresses in the pier are
recovered only at those times at which maxima occur.
b. results
The histories of absolute Z-direction acceleration for four nodes
along the crest of the pier were averaged and plotted versus time; the
resulting acceleration time history is shown in Figure 11.14. Although
the earthquake acts on the structure for 20 seconds, peak values were
found to occur in the 7-to-9 second interval; consequently, only the
first 10 seconds of response are shown. From Figure 11.14 it is seen
that the peak crest acceleration is about 1.2 g's.
Figures 11.15, 11.16, 11.17 and 11.18 are principal stress time
histories covering the first 10 seconds of response. Figures 11.15 and
11.16 show minimum and maximum principal stress, respectively, developed
at the centroid of element 14; element 14 is located at the pier base,
upstream face (i.e., at the pier "heel"). Figures 11.17 and 11.18 are
331
"-a
> z
l-QZ
o: D
i-'^,
•
— OUJ
2 — a
cezu
oEa
b-Z
-iDin
CC UJ
UOK
20
u-a
00
lu — a:
CZCEUJ
"" ' " " 1 " M 1 , ,, 1 1 1 I..), ,.
I SDb
NBIiUy31333b
33Hy3Ab
332
33
fii anos
333
34
334
M 0I13S
SS3^i£-Ccl
CIDi'iN3a
35
£1 anss
ss3yis-id
335
36,,
336
ST anos
aioyiN33
37
plots of minimum and maximum stress, respectively, predicted at the e.g.
of element 15 (at the pier "toe"). The peak values of principal stress
predicted in the pier heel and toe regions are sumnarized in Table U.S.
Note that the critical values occur at two times: 7.76 and 8.46 seconds.
Since the earthquake can act in either the +Z or -Z direction the maximum
seismic stresses (irrespective of sign) are 480 psi in the heel and 305
psi in the toe.
Tables 1 1. 9 and 11.10 list the minimum and maximum principal stresses,
respectively, in all pier elements at time 7.76 seconds. Similarly,
Tables 11.11 and 11.12 show the min/max stresses, respectively, developed
in the pier at 8.46 seconds. Note that the peak stresses always occur
either in the heel or toe. Table 11.13 shows the vertical (Y) stress
distribution in the pier at time 7.76 seconds. By comparing Tables 11.10
and 11.13 it is seen that the critical stresses in the pier are nearly
vertical in the heel at 7.76 seconds (e.g., in element 14, 480 psi
maximum principal versus 464 psi vertical). Also, from the time history
analysis the maximum vertical stress in the pier heel (i.e.. element 14)
was calculated to be 464 psi (see Table 11.13); this prediction agrees
very well with the 457 psi value predicted by the response spectrum
analysis (see Table II. 7).
337
w
CJ
3
W W «
Saw
vo
00
w D g
H
iH
fo o s
•
.
W H t)
« fe 2
H
H
H
H
w
^
.
u
U
U
fe s
0)
Q)
°^
w
tn
W D
vo
vo
S U
r--
^
H U
.
.
Eh O
r-
00
^^
<
•H
•H
s 0.
W
W
D H CO
Qa
04
S U CO
ys§
o
VO
00
n
3 « &H
**
<N
s cu CO
w
U
s ^
§§g
in
r~-
W t> pq
iH
iH
fe CJ S
W H D
« fe S
H
H
H
H
w
.
u
cJ
u
Pm 2
0)
0
o 2
to
tn
W D
VD
vo
s u
"a*
r--
H CJ
•
•
Eh O
00
r-»
^^
■H
•H
S 04
cn
to
D H CO
CX
a
S U CO
H S W
2; H S
^
IT)
<Ti
o
H « Eh
rn
n
S 0^ CO
1
1
S
o
H
EH
« <
J
W U
W
pq
H O
W
O
O- h5
K
Eh
w
a
o
H
O
O Eh
EH D
Q S
§ •"*
U
h^l H
w g
pL| CO
m H
-. w
Ph CO
H Eh
^^
E4 Eh
K
EH Q
H
CO g
W H
CO O
CO U
M »<
« 04
H
CO Q
w
.^-^
H
^^
Ph
<
H
04
Q
H
O
u ?:
s
H
>H
«
m
04
'
Q
W
^
CO
w .<
04
U
338
HF«nTi\r. {,}<\r THr-'F""
TT'IF ^Trn tiuMi-fp
FIFMCf.T nISPL'^Y "^f T MiiMi-r^
•^r fi\ r F r.rjri'?
JJffr (F riiifPiii
39
= t/MIiJI'-'Ll" PI'Ii'iClPAL STtJFSS/pt^I Um I TS/T TMFSTFP r^UMRFR 3>M^ /
• HP)
1)
, 1 (innt ♦iii.)
. / /'-nt ♦on
fiDOVni F rfl'^ spii I wftY/ HALF OF TYPICAL t'Al/ [ Mfc HiSlOKY AMALYSIS/
PTFO FIFW^Tin.i VTM.V t^l.FMFNTS nni-TO-1/7/
/MlNir^iiM PRINFTPAI ^T'-'FSS/Psr Urj I TS/T 1 1^^ ST c P ^JUl■"^rP 3PH/
SOI in FLFMFrJT CF'TPO F nai. miJ|;<,scs
^\
_^h -?r -71
_S(i -bif -<^?
-/b -88 -ni
-<.in -116 -ji^g
-117 -n? -n<s -HI
-) 1^ -l*^? -1,S4 -1H6
-Idl -i>Jn -PI? 10 -7
-176 -?18 -?«7
-U'i* -?/"j -loo
-1 M -^16 -?'.? -lAO -24
-lf.4 -rJOO -?17 -l^JO -107
.p« _m -c.f, _]-),j -\h?. -191 -?ri8 -?01 -lf>7
-pf, -i<) -Hf, -1?< -ic^.^ -1H3 -?->o -2CS -^06 -?47
-II? -I"i0 -17S -loi -P(jJ -219 -^r,^ -305
-11.1 _i^>, -\U -K" -?ill -?2^ -P;.} -i?-<
-1
-T
-) 'I
-?•)
-;'5
-,"•7
-t;
-1 1
-?o
-TS
- '• 'J
-4S
-7
-,r.
-r>H
-SI
-SS
-66
-7
-\(-
-Tl
-'■I
-12
-H'*
-7
-\f.
-If
-7S
-m
-101
-R
-17
--<Q
-R6
-100
-117
-P
-IR
-A?
-96
-113
-136
-R
-IP
-/.S
-105
-1?A
-W.R
1
-1 1
-^o
-11 1
-)?a
-IS?
-1
-R
-uh
-n.T
-1^^
-lAH
IS
-?n
-■\h
-7T
-110
-1 v
-1
-7
-?7
-10?
-1?
TABLE II. 9
MINIMUM PRINCIPAL STRESSES IN THE PIER
AT TIME 7.76 SECONDS
339
HFAHINr. LIMF THOFF
= (/l.'ArlMUM Pt^IUCTPftL STPFSS/P^I UNlTS/TTMFSTfP NUMHfR Iflfi/
TTi'F ^TF" riUMMFi'
FLF'-'F^T nTSPL'lY' Si'T MiiMi;
Sr^l.T FATTOP
oiiTP'iT STPF9S ro'<i-^OM'"nT
TI'IF C.F OUTPUT
IRH)
n
.77f,UF t()\ )
OPOVTI.I.F "AM <;PTM ^'AY/ H/>I_F OK TYPICAL fiAY/ rl'-IE HISTORY ANALYSTS/
PIFP FLFVATIdrj VIi-W/ FLFMF^'TS 001-10-177/
/MAXT'-'ll" PPTMrlPA( STr-fSS/PSI UM ] TS/T I MF^^TF P NUMPFR 3R<^/
SOLIn FLFMFNT CFMTPniliAL STPFSSFS
11
3't
30
?!1
l*.
\?
?\
IS
l'^
}9
20
1>^
PO
■>u
3?
3'?
31
33
37
6«
*^0
'W
Uh
78
1?'^
1?7
QA
70
QH
??h
2?')
17^
1 l'^
P7
?^7
?'*3
1 fiR
IT^
104
31?
?h'=-
204
144
no
3f>'«
2"!
21*^
li^^S
112
'.^l
inu
21^
ICS
no
6BH
?oq
21'.
I'^l
10"")
11
n
10
7
22
14
14
7
?_Q
22
lb
8
32
?3
14
5
34
2'5
19
9
4 6
37
30
34
<^6
46
4l
27
64
SO
30
8
6fl
44
14
2
7?
44
24
7
7rf
S4
36
24
H2
^1
4H
45
«3
64
bJ
44
PO
62
S2
46
74
•^s
44
38
2
1
-1
12
10
^7
8
3
47
20
0
11
17
5
»
48
12
2
4S
26
6
36
12
-6
24
3
7
IS
-3
-q
TABLE 11.10
MAXIMUM PRINCIPAL STRESSES IN THE PIER
AT TIME 7.76 SECONDS
3A0
41
HF en TNT, LIMF THi-'ri
(/MNI"!!' Pi'IlirH^AL '^T'^F'^'^/P'^I UMlTS/IIMf STFP NUMMtH 4?3/
oiiTPiir <;T-^rss ro'M'Pi.Fvr
TTMf OF OUTPUT
I)
.U'Oiit 'C^l
.Haf,nt + 01 )
O'^OVTLLF ■>'»''' tPTMKIY/ t.iMF OF TYPICAL P^Y/ T I MF HISTORY ftN/VLVSIS/
PIFU FIFVATIOri WTi^'V K.Pi'FMTS Oni-fn-177/
/MI'ITWIIU Pt?(NrliMI ST^TSS/MSI UM I T S/T I ^FSTF (' NUMfiFK A??/
SOLIO FLFMFMT Crt'TPOIr^AL ^.T^-'FSSfS
-31
-?0
-IS
-13
-1?
-IP
-1?
-10
-7
_r>
-?r
-I*^
-If.
-pfN
-P'i
-?3
-!'->
-1-4
-7
-2
-??
-?1
-?I
-?5
-34
-?8
-?1
-14
-7
-1
-2Q
-Pf-
-PU
-?«
-3V
-Tfl
-?1
-12
-4
1
-3^
-3"
-?ft
-pQ
-a4
-3S
-?s
-l-^
-7
-9
-p
-4?
-3 3
-?7
-30
-i,Q
-39
-30
-24
-2H
-23
-7
-S1
-<4 0
-31
-33
-S5
-4f.
-37
-33
-20
T
-32
-13
-IS
-ftq
-r,o
-4 3
--{Q
-t^h
-•^1
-39
-2?
-2
-fl
0
\?.}
-1)Q
-P^
-^;q
-70
-S^
-32
-n
0
1
-6
^l'^^
-?10
-l'^3
-ijf,
-7 4
-■^J
-3(1
-14
-1
-1
-4
-U
-4
?A7
-?17
-1»^3
-11-1
-79
--^7
-37
-23
-IP
-26
-3S
-R
-2
?7H
-^M
-1 7/.
-1?1
-M T
-S9
-42
-33
-32
-1ft
-33
-?n
-s
31?
-P^P
-Ifl?
-IP',
-■*'^
-S9
-au
-3 7
- <4
-T3
-26
-9
s
3^1
-?^\
-1«I
-IP'S
- J3
-Sh
-u ">
-Jli
-n
--•7
-17
- 4
-s
loa
-?'^1
-17.J
-1P3
-7'y
-SI
-3'>
-2>'
-24
-pri
-9
3
7
TABLE 11.11
MINIMUM PRINCIPAL STRESSES IN THE PIER
AT TIME 8.46 SECONDS
341
TJMF CTFP ri'lMPF"
srii"^ Ff.rKip
TTMF rr niiTPUT
riPovTLLf I'AM '■.PTM '/AY/ MAi.F "F Ty^ir/vL nav/ iimf history ftMAUrsis/
pjfrp HFv/\TTO'l Wf-w/ ritfiFt'TS 0" I -Tl)-1 77/
/MrXT^MM ppT'Nirl'^/M ^T'HS^/P';! HMITS/TIMFST!- P MDMnFM '*?^/
SOI in FLFMFNT CF^'TP'^ln''L ST^Ji^SSFS
(/MAXIMUM
in^irjriP
( a rM )
( II
( .1
^not*r»^)
( '1
-Mlf ♦01 )
irjrlP/M. ST^FSS/PSI ljr<jns/TIMFSTFP NUMHF« ^?3/
n
1 1
9
?n
?4
?b
P.l
?h
Pf>
19
13
37
'.^
47
bX
(^n
?5
47
S3
M
fi9
R^
9S
PB
'-.f^
'^'7
7V)
P9
ICfS
14R
TO
t~ S
7ii
H9
10 4
1?4
1P4
75
T^
7 3
R';
101
1^2
140
14B
170
ri
79
nit
n^
139
lf<6
193
-S
f.
?.
3'i
"?
ion
1^3
14H
18H
a'-.i
9
11
P?
ino
1?J
153
192
a's'^
Q
?■(
7 0
93
117
147
IBO
?n?
ISO
IR
?4
!<=>
Ut~:
HP
in?
1 If-.
lh>4
17fl
ISS
fl6
?n
1 1
->.'^
hi
9 9
W'*
ISS
KQ
lh2
133
79
'.
?(-
S9
9<'
Ic--^
147
l*^!
1^4
l'-3
19?
?
?1
■^3
nr.
1 1 1
140
l'-4
lf>l
173
1"7
23f>
_p
1h
'4 9
M ■(
I 1 I
1 10
K-n
1^0
17S
1R9
177
TABLE 11.12
MAXIMUM PRINCIPAL STRESSES IN THE PIER
AT TIME 8.46 SECONDS
3A2
43
HEADING LlNf THR^E = (/VERTICAL STRESS IN P lER/V-OIRECT lON/PSI UNITS/TIME STEP NUMBER 388/
TIME STEP NIIMHLP = ' 388)
ELEMENT DISPLAY SET NUMBER = I
SCALE EACTOP = ' .IOOOE'04.
OUTPUT STRESS COMPONENT = ( 2)
TIME OF OUTPUT = < .7760E»on
OROVILLE DAM SPILL»*AY/ HALF OF TYPICAL BAY/ TIME HISTORY ANALYSIS/
PIFR FIFVATION VIEW/ ELEMENTS OOl-TO-177/
/iERTICAL STRESS IN P lER/Y-D IRECT lON/PSI UNITS/TIME STEP NUMBER 388/
SOLID ELEMENT CLNTROIDAL STRESSES
17 K 1? 10 7 'i 2 -1 -5 -13
15 u )3 15 1ft 10 2 -8 -20 -36
20 18 18 \'i 21 11 -2 -'8 -38 -«>1
2b 23 21 22 25 11 "7 -28 -52 -91
3? 27 23 23 28 9 -U -39 -71 -71 -'.2
-20 -52 -T* -96 -163
-27 -57 -95 -159 1* "6 9
30 35 0 -34 -73 -127 -191 -3
42 28 -10 -51 -99 -U'. -197 -<•
77 20 -17 -64 -107 -150 -154 -80 -4 -24
□7 32 -19 -63 -106 -141 -148 -113 -68 -36
39 31 25 24
48 39 3U 26
67 58 42
120 120 H4
221 223 159
266 235 171
31, 255 181 108 41 -16 -63 -103 -132 -140 -131 -125 -98
362 277 189 113 46 -13 -6l -98 -124 -136 -140 -156 -230
,15 ^9 -,0 -57 -94 -119 -133 -145 -179 -221 -244
416 290 190
464
280 191 117 51 -7 -54 -90 -115 -133 -152 -185 -209 -188
TABLE 11.13 VERTICAL (Y) STRESSES IN THE PIER
AT TIME 7.76 SECONDS
343
III. TWO DIMENSIONAL ANALYSIS WITH HYDRODYNAMIC INTERACTION
A. three dimensional dynamic analysis which includes hydrodynamic
interaction is beyond present research development for a structure of
this type. It is possible to estimate the magnitude of this effect
from the analysis of a two dimensional model with similar dynamic
properties.
A. Analysis Without Interaction
A two dimensional finite element model was selected with the same
mesh idealization as used in three dimensional model of the pier (Figure
II. 5). Normal concrete properties were used except the weight density
was scaled so that the fundamental period of the two dimensional model
was the same as the fundamental period of the three dimensional model
without hydrodynamic interaction. From Table III.l one notes that the
maximum stresses obtained from this two dimensional model are in
excellent agreement with the three dimensional analysis. This confirms
the results from the three dimensional analysis which indicated \iery low
stresses in the breast wall.
B. Analysis With Interaction
The analysis of the two dimensional model with hydrodynamic inter-
actions was accomplished using the following program:
*EADHI - "A Computer Program for Earthquake Analysis of Gravity
Dams Including Hydrodynamic Interaction," by P. Chakradarti and
A. K. Chopra, May 1968, College of Engineering, U.C. Berkeley,
California.
From Table III.l the results indicate an increase in critical
stresses at the toe and heel of approximately 20 percent due to hydro-
dynamic interaction.
344
45
2/D ANALYSIS
W/ HYDRODYNAMIC
INTERACTION
B
■H
+J
PI
-H
e
vo
00
o
LD
r--
00
0)
e
■H
4->
\
X
e
1J3
\
in
00
\
vo
ro
2/D ANALYSIS
W/0 HYDRODYNAMIC
INTERACTION
e
•H
-P
-H
00
H
\
o
n
e
•H
+J
\
\
en
vo
'I'
00
•\
VD
3/D ANALYSIS
W/0 HYDRODYNAMIC
INTERACTION
g
•H
+J
•H
00
ro.
\
in
o
n
e
•H
-P
e
r-
o
00
1^
»*
00
VD
n
o
H
u
o
EH
in
rH
EH
W
S
M W
O J
Eh W
345
46
C. Extension to Three Dimensional Analysis
A reasonable engineering approximate solution to the three dimensional
hydrodynamic interaction is to apply the + 20 percent correction to the
results obtained from the three-dimensional analysis without interaction.
This is a suggested approach for a horizontal earthquake. The effects of
hydrodynamic interaction due to a vertical earthquake have not been
considered.
346
47
IV. TRANSVERSE EARTHQUAKE ANALYSIS
The monoliths of the flood control outlet structure are separated
by contraction joints. The actual size of these joints must be measured
in the field. The monoliths which do not contain gates are solid and
are short relation to the two monoliths with gates. Therefore, it is
reasonable to evaluate the stresses in the gate monoliths only due to
a transverse earthquake. Because of the special geometry of these
structures the maximum possible transverse displacement would be equal
to the size of two contraction joints regardless of the magnitude of
the earthquake.
Furthermore, transverse displacement of the gate monoliths will
cause bending in the piers between the foundation and the roof of the
intake which is a distance of approximately 34 ft. A good estimate of
bending developed in the pier can be calculated by assuming the pier
to act as a fixed end beam subjected to a support displacement equal
to the size of two construction joints. For a 5 ft. pier, the extreme
fiber strain will be 0.0012A where A is the contraction joint displace-
ment. Since these piers are reinforced a damage evaluation can be made
from normal reinforced concrete theory.
347
V. VERTICAL EARTHQUAKE
For a structure of this type the modes of vibration which have
significant vertical components have a very high frequency—greater
than 50 cycles per second. For this high frequency the structure moves
as a rigid body at the earthquake acceleration. Therefore, a very good
approximation of the maximum stresses due to vertical earthquakes can
be calculated by multipling the gravity stresses by the maximum accelera-
tion (given as a fraction of gravity).
The vertical stresses due to gravity are given in Table II. 1. If
the maximum acceleration due to a vertical earthquake was 30% of gravity
the vertical stress at the heel will vary +90 psi or from -210 psi to
-390 psi.
348
49
VI. FINAL REMARKS
This report summarizes the results of a three dimensional finite
element analysis of the Oroville Dam Flood Control Outlet Structure.
Hydrostatic, prestress, gravity and horizontal earthquake results are
presented separately. In addition, approximate methods of analysis are
given for hydrodynamic interaction and for transverse and vertical
earthquake behavior.
349
CHAPTER VII
SEISMIC ANALYSIS OF THE
THERMALITO DIVERSION DAM
Commentary
As a result of the August 1, 1975 Oroville earthquake, of
magnitude 5.7, the Department found it appropriate to reanalyze the
Thermalito Diversion Dam (Figures 187 and 188) using a stronger earth-
quake (see Chapter V) , and the latest techniques in seismic investigation.
An earthquake study, monitored by the Department, was conducted
under a consulting agreement with Dr. Anil K. Chopra. Dr. Chopra's
results and conclusions were presented in his report, "Earthquake Response
Analysis of Thermalito Diversion Dam". That report is presented in
this chapter (beginning on page 355 ) .
Dr. Chopra performed a dynamic two-dimensional response analysis
of the dam using the finite-element method. The Department agrees with
the methods used and conclusions presented in his report.
The Department investigated the Dam for sliding, utilizing the
shear-friction equation
CA + N tan 0
Q = . A cohesion value, C = 3447
kPa (500 psi) , produced a shear-friction factor of approximately 5. This
is considered a safe value against sliding.
351
Figure I87. Plan and Elevati
352
Figure 188. Typical Sections
353
EARTHQUAKE RESPONSE ANALYSIS OF THERMALITO DIVERSION DAM
by
Anil K. Chopra
355
EARTHQUAKE RESPONSE ANALYSIS OF THERMALITO DIVERSION DAM
by
Anil K, Chopra
Introduction
The Department of Water Resources, State of California, entered
into an agreement with Dr. A. K, Chopra to "perform structural analy-
sis using finite element techniques of Thermalito Diversion Dam".
The agreement stipulated that "the analysis will employ the most
suitable dynamic methods applicable to the specific structures".
Results of this analysis for the groujid motion specified by
the Department of Water Resources, State of California, are presented
in this report.
The scope of the work necessary for structural analysis of
Thermalito Diversion Dam was first discussed and outlined in a
preliminary meeting between Dr. Chopra and Denzil Carr of the
State Department of \\later Resources. Subsequently, results from
preliminary analyses were discussed at a meeting on September 7^
1976 between Dr. Chopra and Messrs. Sam Linn, Edgar Najera, and
Vernon Persson of the State Department of Water Resources. The
series of analyses and results required by the State Department of
Water Resources were defined. In accordance with these requirements,
a draft report was submitted on November 4, 1976.
Messrs. Linn, Najera and Don Steinwert, State Department of Wate
356
Resources, coiiunented on the draft report at a meeting on February 25, 1977 with
Dr. Chopra. The draft report has been revised and expanded to
account for these comments, resulting in this final report.
The draft report of November 4, 1976 was based on analyses of the dam for
the ground motion originally recommended by the Special Consulting Board for the
August 1, 1975 Oroville Earthquake (Fig. 1). The Board made supplementary
recommendations regarding ground motions to be considered in their report of
November 23, 1976. After a study of this supplementary recommendation, it was
concluded in a report of March 4, 1977 (see Appendix) that, for analysis of
Thermalito Diversion Dam and Oroville Dam Flood Control Outlet Structure, there is
no need to supplement the ground motion originally recommended by the Board, for
which the structures had already been analyzed. All results presented in the main
body of this report are therefore based on analyses for the original ground motion.
Finite Element Models
The dynamic response analysis of gravity dams is done by the finite element
method, assuming that monoliths act independently of each other and in a condition
of plane stress; in practice a one-foot thick slice of the dam is analyzed. If
the foundation material is significantly softer than the dam concrete, then it
may have a significant effect on the dynamic behavior of the dam and must be
included in the finite element idealization. In the case of Thermalito Diversion
Dam, however, the properties of the foundation rock are such that it should
have only insignificant influence on the dynamic response of the dam. Furthermore the
degree to which the response is affected depends strongly on the depth of rock
included in the finite element model, and where rock essentially similar to the
rock under the dam and near the ground surface may be asumed to extend to great
depths -- as in the present case — there is no rational basis for defining the
limits of the finite element model. Consequently, in this investigation the
357
I
concrete monoliths were assiamed to be supported on a rigid base, and the specified
earthquake ground motion was applied at the base. It was concluded that no greater -;
reliability in the dynamic response results could have been achieved by including '
an arbitrary layer of rock under the monoliths in the finite element model, even
though it is common practice to include such a layer in performing purely static
analysis.
The finite element models defined for the analysis of monoliths 10, 12 and
18 are shown in Figs. 2-5. They all employ the isoparametric quadrilateral
element used in the SAP program developed by Professor E. L. Wilson at the
University of California, Berkeley. They have graded meshes, with slender elements
near the monolith faces to better define the stresses in those regions. In each
case, the number of elements through the upstream-downstream direction and the
number of rows of elements through the height, are considered to be sufficient
to provide good definition of the stress, especially in the critical zones.
Two different finite element models were used to represent monolith 12:
The one shown in Fig. 2 which includes only the monolith itself was defined for
purposes of preliminary analysis. The other shown in Fig. 3 includes an
approximate two-dimensional model of the appurtenances: pier, bridge and radial
gate. This model, although not appropriate for determining the details of
dynamic response of the appurtenances themselves, is believed to be adequate
to represent effects of the appurtenances on the dynamic response of the
monolith, which is the main concern of this investigation. P
The modulus of elasticity of the finite elements included in the model of
Fig. 3 to represent the piers was set at 5/45 (=width of pier/width of monolith)
of the value for concrete. The density of these elements was set in a slightly
different ratio to include the weight of the radial gate and other equipment.
For the top-most row of elements, the density was increased to include the
weight of the bridge, but the modulus of elasticity was taken as that of the concrete
358
The static and dynamic analysis of all finite element models were performed
by the computer program EADHI developed at the University of California, Berkeley.
This program includes the effects of interaction between the dam and water, and
of water compressibility.
The properties of concrete were taken as those provided by the Department of
Water Resources, State of California, for the 2-1/2 sack mix, which is used
throughout the monoliths except for a small thickness near the exposed surfaces
and galleries:
6
• Modulus of Elasticity = 5.1 x 10 psi
• Poisson's Ratio = 0.17
• Unit Weight = 155 pcf
Earthquake Response Analysis
Before proceeding with analysis of the dam, the computer program EADHI was
extended to handle water level above the crest of a monolith. This capability
is necessary to analyze overflow monoliths 10 and 12.
Several preliminary results were generated to obtain an overall impression
of the dynamic response of the dam. For this purpose the finite element model of
Fig. 2 for monolith 12, excluding the appurtenances, was analyzed.
The frequencies of the first three natural modes of vibration are shown
in Table 1. It is apparent that the dam has rather high vibration frequencies.
Stress analyses were performed considering the static loads assumed to be
acting prior to occurrence of an earthquake. These include the dead weight of
the monolith, and the hydrostatic pressure of the water when the reservoir is at
the normal level (El. 225).
The dynamic response of the finite element model of Fig. 2 to the specified
ground motion (Fig. 1) assxamed to act in the upstream-downstream direction was
determined. Only those modes with frequencies less than 30 Hz were considered
359
Table 1: Natural Frequencies of Vibration of
Monolith 12 without Appurtenances
Mode No.
Natural Frequencies , cps
Dam Only
Dam with Water
at EL. 225.0
1
2
3
14.5
30.4
34.8
8.5
29.1*
28.9*
The natural vibration modes of the dam without water are numbered
according to standard convention: The natural mode having the lowest
vibration frequency is called the first mode, that having the next
higher frequency is the second mode, etc. Because hydrodynamic
interaction effects depend on the frequency and shape of the vibration
mode2, the vibration frequencies of the three modes of the dam are not
in increasing order when effects of water are considered. However,
this is of no consequence in the analysis, because all the modes which
have significant contributions to the total response are included.
360
in the dynamic response analysis, because the earthquake motions are not defined
accurately for higher frequencies. Analysis by the computer program EADHI leads
to the time history of horizontal and vertical displacements at all nodal points
of the finite element system and the time history of the three components of total
stress — static plus dynamic — in all finite elements. Only a small portion of
these results which is most pertinent to evaluating safety of the dam is included
here.
Fig. 6 shows the contours of "envelope" values of the maximum principal
stress. These are peak values of maximimi principal stress — the most tensile
stress — developed in each element at any time during the earthquake; they are
not all concurrent values. The static stresses have been combined with the
dynamic stresses (taking proper account of the tensorial nature of the stress
components) so that these contours indicate the absolute magnitude of the tensile
stresses that must be resisted by the monolith during the earthquake. Of major
significance are the zones of tensile stress at the downstream face just above
the bucket and at the upstream edge of the base. The latter zone is in part a
consequence of the discontinuity between the concrete and the assumed rigid base.
It is in part the result of a singularity in the mathematical model under study
and that part could be removed by changing the mathematical model. However, this
singularity is of little concern in this case because the maximum tensile stress
is about 310 psi, which, as will be discussed later, is considerably below the
tensile strength of concrete.
The final results of critical stresses in Monoliths 10, 12 and 18 which are
obtained from dynamic analysis of the response of finite element models of
Figures 3-5 produced by the specified ground motion (Fig. 1) are presented next.
Fig. 7 shows the contours of "envelope" values of the maximum principal
stresses in Monolith 12. These are total stresses including those due to static
loads. As mentioned earlier, the two-dimensional finite element model for the
361
appurtenances above the monolith is suitable for including their effects on
stresses in the monolith, but is too crude for determining the response of the
appurtenances themselves. Consequently stresses in the appurtenances are not
presented. Of major significance in Fig. 7 are the zones of tensile stress on ■
the downstream face just above the bucket and the upstream edge of the base. It
is of interest to note that these envelope values of stresses do not differ
significantly from those computed without including the effects of appurtenances
(Fig. 6) .
In order to further examine the response, contours of the instantaneous
maximum tensile stresses are presented in Figs. 8 and 9 at two instants of time:
when the tensile stresses on the downstream face attain their peak value (7.35
sees after beginning of the earthquake motion) and when the tensile stresses at
the upstream edge of the base reach their peak value (t = 8.47 sees). It is
apparent that at each of these time instants, stresses in a significant portion
of the dam are compressive.
Fig. 10 shows the contours of "envelope" values of the minimxam principal
stresses — the most compressive stresses — developed in each element at any time
during the earthquake, including both static and earthquake effects.
The corresponding contours of "envelope" values of the maximum and minimum '
principal stresses for Monolith 10 are shown in Figs. 11 and 12 and those for
Monolith 18 in Figs. 13 and 14. These are similar in general form to the results
obtained for Monolith 12 but are significantly smaller in magnitude. These
shorter monoliths, which have very high natural vibration frequencies, do not
respond dynamically to any great extent.
Summary of Results
The principal features of these dynamic analysis results may be summarized
as follows: I
362
1. The maximum compressive stresses (Figs. 10, 12 and 14) due to both static
and dynamic effects were about 200, 425 and 350 psi respectively in Monoliths
10, 12 and 18. These are well within the capacity of this concrete and
constitute no cause for further consideration.
2. The maximum tensile stresses due to both static and dynamic effects were about
200, 310 and 225 psi respectively in Monoliths 10, 12 and 18. Later, these will
be compared with the tensile strength of concrete.
Tensile Strength of Concrete
Although standard criteria for design of concrete dams do not allow tensile
stresses of these magnitudes , evidence is available to support the conclusion that
significant dynamic stresses in tension can be supported by sound concrete.
3,4
Experiments conducted in Japan showed that static tensile strength of concrete
is about 8 to 9 percent of the static compressive strength, which is similar to
the usual assumption of a 10 percent ratio. Moreover, under dynamic conditions,
at loading rates to be expected in concrete gravity dams subjected to intense
earthquake motions, these experiments showed that the concrete strengths are
significantly -- up to 50 percent -- higher (both in tension and compression) than
under static loading. Similarly, recent tests in the United States on mass concrete
cores from three dams showed, on the average, a corresponding increase in tensile
strength of 67 percent .
Further evidence of the dynamic tensile strength of concrete was provided
by the performance of Pacoima Dam during the San Fernando Earthquake of 1971.
The ground motion experienced by this structure must have been very intense;
accelerations exceeding Ig were recorded near the dam. Analyses carried out at
University of California, Berkeley, of dynamic response to that motion indicated
that the dam must have developed maximum tensile stresses in the order of 750 psi.
Yet no evidence of cracking could be found on either face of the dam.
363
On the basis of both the laboratory test data and the experience at Pacoima
Dam, it is reasonable to assume that the concrete in Thermalito Diversion Dam can
resist tensile stresses of at least 10 percent of the static compressive strength,
increased by 50 percent to account for the faster loading rates during vibration
of the dam.
Comparison of Analytical Results and Tensile Strength
As mentioned eariler, the maximum compressive stresses predicted by
analyses are well within the capacity of concrete and are therefore of no
concern.
The corresponding maxim\im tensile stresses in various parts of Monoliths
10, 12 and 18 are summarized in Table 2. Also included are the static compressive
strength values, provided by the State Department of Water Resources, and
estimates for dynamic tensile strength, based on the preceeding section of this
report, for the four concrete mixes employed in the dam (Fig. 15) .
It is apparent that the tensile stresses predicted by analyses are less than
one-half of the tensile strength of the concrete. The concrete is therefore
capable of safely resisting these tensile stresses.
The earthquake ground motion specified by the State Department of Water
Resources, for which only a single horizontal component of motion was provided,
is the excitation for which all the analyses presented above were carried out.
2
However, research studies have shown that the contributions of the vertical
component of ground motion to the response of concrete gravity dams are
significant. Even for vertical ground motion, hydrodynamic pressiires act in
nearly the horizontal direction on a nearly vertical upstream face, thus causing
lateral response. Although this additional lateral response can be quite
significant for short dams, the available margin in tensile strength (see Table 2)
should be sufficiently large to keep the total (due to horizontal
364
10
^
+J
•r<
rH 00
o
in
o
+-
0 --1
in
O)
r-~
<C
c
rH
CN
r-t
Z
w
Q
m
SI
0)
u
4J
CO
0)
5
i-H
■iH
-rH
iH (N
o
o
o
o
w
0 •-{
in
rH
o
^
c
c
CN
n
CN
OJ
(1)
0
EH
g
s
■ri
£
X
+J
•H
o
O
in
+-
H O
in
o
r-
<
0 >H
rH
CN
s
c
0
s
-H
U)
a
O <U -
■•^i •-* jq
in
in
o
o
CM
r-
in
r-
S CO CTi
in
vD
r-~
00
c c c
>i 0) 0)
Q EH V<
+J
w
•rH
Q) (0
> a,
•H -
o m xi
-rH U) -P
o
o
o
o
o
o
o
o
4-1 0) en
in
in
o
00
(TS k C
n
»*
in
in
+J ft Q)
w g n
0 -P
u w
X
•H
s
o
u
0)
(0
M
(tJ
X
■p
w
o
Ul
o
0)
(0
m
M
rH| <N
tn
rH|CV)
en
u
c
(N
n
ro
-*
0
u
0)
fO
u
Q
Q)
lO
4J
o
fo
<u
0)
ifl
X
5
fa
§
o
3
V4
g
0)
CQ
H-l
0
Jo
^4
o
-H
<u
4J
i«
!h
u
m
4J
0)
4-1
c
(U
>4
+J
Ul
3
0)
Ifl
C
ft
0
CP
eu
H
D
Q
O
365
and vertical ground motion) tensile stresses within the available tensile strength.
Conclusion
Based on results of dynamic analyses and available data for concrete strength
it is concluded that Thermalito Diversion Dam should be able to resist the stresses
expected during the earthquake ground motion specified by the State Department of
Water Resources.
References
1. Chakrabarti, P., and Chopra, A.K., "A Computer Program for Earthquake Analysis
of Gravity Dams Including Hydrodynamic Interaction," Report No. EERC 73-7,
Earthquake Engineering Research Center, University of California, Berkeley,
May 1973.
2. Chakrabarti, P., and Chopra, A.K. , "Earthquake Response of Gravity Dams Includii
Reservoir Interaction Effects," Report No. EERC 72-6, Earthquake Engineering
Research Center, University of California, Berkeley, December 1972.
3. Hatano, T. , and Tsutsumi, H., "Dynamical Compressive Deformation and Failure of
Concrete Under Earthquake Load," Report No. C-5904, Central Research Institute
of Electric Power Industry, Tokyo, September 30, 1959.
4. Hatano, T. , "Dynamical Behavior of Concrete Under Impulsive Tensile Load,"
Report No. C-6002, Central Research Institute of Electric Power Industry,
Tokyo, November 5, 1960.
5. Raphael, J.M., "The Nature of Mass Concrete in Dams," Douglas McHenry
Symposium Volume, American Concrete Institute, Detroit, Michigan, 1977.
366
IZ
O
LU
LU
o
00
O
CD
O
o
CVJ
o
o
o
o
o
GO
o
O
o
o
o
1
o
o
o
(0 o
U <4-l
0) -H
(9) N0llVd3n30DV
367
UJ
LlJllJ
UJ
UJ
368
14
TOTAL NUMBER OF
NODAL POINTS =164
FINITE ELEMENTS = 145
)0'. 0
Fig. 3 Finite Element Mesh: Monolith 12 with AppurteneUices
369
EL. 233.0
EL. 225.0^
TOTAL NUMBER OF
NODAL POINTS = 114
FINITE ELEMENTS =
EL. 205.0
EL. 145'. 0
100
EL. 130.0
Fig. 4 Finite Element Mesh: Monolith 10
370
16
EL. 233.0
EL.225.0^4r
EL. 214.0
TOTAL NUMBER OF
NODAL POINTS = 162
FINITE ELEMENTS = 136
EL. 140'. 0
Fig. 5 Finite Element Mesh: Monolith 18
371
372
18
(0 3
2 ft
O -H
rH 1-1
0) O
> c
C 0
373
374
20
375
376
22
MAXIMUM TENSION
Fig. 11 Envelope Values of Maximum Principal Stress (Static + Dynamic) ;
Monolith 10
377
MAXIMUM COMPRESSION
Fig. 12 Envelope Values of Minimum Principal Stress (Static + Dynamic) ;
^^onolith 10
378
1
24
MAXIMUM TENSION
Fig. 13 Envelope Values of Maximum Principal Stress (Static + Dynamic)
Monolith 18
379
25
MAXIMUM COMPRESSION
Fig. 14 Envelope Values of Minimum Principal Stress (Static + E)ynamic)
Monolith 18
380
26
CO
X
_l
o
z
o
o
UJ
>
o
tj
<
m
^
^
^
Li
o
<
<
Ui
en
CO
X
o
z
o
<
CL
CO
381
27
APPENDIX
383
28
RE: Report (dated November 23, 1976) of the Special Consulting Board for the
August 1, 1975 Oroville Earthquake to Mr. R. B. Robie, Director, Department
of Water Resources, State of California.
Board Recommendation:
"The Board recommends that for critical structures with high fundamental
frequencies, the previously recommended time-history of earthquake be supplemented
by a time history meeting the high frequency (10 Hz or greater) requirements
specified by the Nuclear Regulatory Commission in its Regulatory Guide No. 1.60,
with the spectrum scaled to 0.4g at zero period."
Response (Prepared by Anil K. Chopra)
Two pseudo-acceleration response spectra, both for damping ratio of 5 percent,
are presented in the attached figure: one for the earthquake motion previously
recommended by the Board; and the other is the spectrum specified in the AEC (now
NRC) Regulatory Guide No. 1.60, scaled to 0.4g at zero period. The natural periods
of vibration of Thermalito Diversion Dam and Oroville Dam Flood Control Outlet
Structure lie within the period range 0 to 0.15 sec shown in the attached figure.
It is apparent that in the range of vibration periods of interest there is
little need to supplement the ground motion previously recommended by the Board,
for which the structures have already been analyzed.
If each spectrum was normalized with respect to its ordinate at zero period,
in the range of periods of interest, ordinates of the normalized AEC Regulatory
Guide No. 1.60 spectrum would be significantly larger than ordinates of the
normalized spectrum for the ground motion previously recommended by the Board.
However, the actual (without normalizing) spectra do not have the same
relationship because the ordinates at zero period are different by a factor of
50 percent :0.5g for tlie ground motion previously recommended by the Board, and
0.4g for the AEC Regulatory Guide No. 1.60 spectrum.
March 4, 1977
385
o
n
CJ
(/)
c u
0 -P
o
-H u
liJ
4J (U
0 a
(O
^ w
to
1
-O 0)
Q
c W
3 c
O
0 0
U ft
o to
iij
0
Q.
l4-( O
ySD
O
U 0
Q) 2
0) -H
0) 3
C O
0
in
tfl cr
o
>
0) 0)
O T3
m C
•H (0
ft v^
o
6-r NOiiva3n3oov nvdi03ds
386
30
April 13, 1977
Professor George W. Itousner
Ittvlslon of Civil Ensineering
and Applied Mathematics
California Institute of Technology
1201 East California Boiilevard
Pasadena « CA 91109
Dear Professor Houaneri
In the November 23, 1976 report of the Special
Consulting Board for the August 1, 1975 Oroville
Earthqviaice, the Board recommended that the adopted
time history of earthquake motion be supplemented
by a time history of higher frequencies.
Dr. Anil Chopra of UCB investigated the effect
of this recommendation. His findings are enclosed.
Please give us your comments at your earliest
eonvenlence .
Sincerely,
ISonald C. Stelnwei^, Chief
Structural Unit
Sesign Branch
Civlsion of Design and
Construe ti on
Eno.
ENaJerarmrs
bfb: H, H. Eastin w/attach
R, B, Jansen w/attach
K. 0, Barrett w/attach
E, C. James w/attach
387
GEORGE W. HOUSNER
I20t EAST CALIFORNIA BLVD.
FASAOENA. CALIFORNIA 9II2S
April 26, 1977
Mr. Donald C. Steinwert
Division of Design and Construction
Department of Water Resources
P. O. Box 338
Sacramento, California 95802
Dear Mr. Steinwert:
This is in reply to your letter of April 13th, concerning
Dr. Chopra's investigation on the OroviUe facilities. I am
satisfied from Dr. Chopra's statement and the spectrum
curves that he shows that further analysis need not be made
with the ground motion specified by the Nuclear Regulatory
Commission in its Regulatory Guide No. 1.60, with a spectrxim
scaled to 0.4 g at 0. The ground motion originally recommended
by the consiolting board is adequate.
GWH:bb
lEORGEW. HOUSNER
j;^^-^;^--^
388
CHAPTER VIII
REAPPRAISAL OF SECONDARY STRUCTURES
I Introduction
As a result of the August 1, 1975 Oro-
ville earthquake, the Department of
Water Resources found it appropriate to
reanalyze the major structures of the
Oroville complex using both the "latest
state-of-the-art" dynamic analysis and
the Reanalysis Earthquake described in
Chapter V. It was determined that non-
critical structures could be reassessed
using a lesser seismic force if a reanal-
ysis was necessary. The Board would
defer its recommendation as to the need
for reappraisal of these secondary struc-
tures until the evaluation of the
critical structures is complete.
After evaluating how a structural failure
would affect project operation, possible
loss of life and property, and the possi-
bility of failure, the Department recom-
mended what further seismic analysis
is needed for the facilities in this
report. The locations of these facil-
ities are shown in Figures 189 and 193.
Fish Barrier Dam
Description
The Fish Barrier Dam is a concrete
gravity structure (Figures 190 through
192) founded on generally fresh and hard
rock consisting of meta-andesite and
meta-conglomerate rocks. The dam con-
sists of a central low-overpour section
250 feet long, a high-overpour section
on either side of the lower section with
a total length of 54 metres (176 feet) ,
and a non-overpour section on the right
abutment 53 metres (174 feet) long. The
low-overpour section consists of a
gravity section with a cantilevered
reinforced-concrete crest apron extending
2.7 metres (9 feet) downstream of the
dam face, and two aeration piers. The
other two sections are gravity concrete
sections. The maximum structural height
of the dam is 28 metres (91 feet) . A
thorough inspection of the dam after the
August 1, 1975 earthquake revealed no
damage to this facility.
Original Seismic Analysis
The original seismic analysis consisted
of a pseudostatic analysis; an accelera-
tion coefficient of O.lg acting either
downstream or upstream was used. The
hydrodynamic force was determined using
the Westergaard formula and an assumed
natural period of 1 second for the
structure. In addition to the earth-
quake force, the pseudostatic analysis
included all normal forces including
river flows up to 50,000 cfs. Utilizing
these loading conditions, the structure
was analyzed at several levels for maxi-
mum and minimum principal stresses,
safety against sliding (f ) , and the
shear friction factor of safety
(s
sf
f V + r A
H
•) . In addition.
the overturning safety factor was
checked for the Federal Power Commission
review in 1972.
On the basis of the preceding analysis,
the maximum principal compressive stress
was approximately 120 psi, and maximum
tensile stress was about 10 psi. Both
are considerably lower than the allow-
able stress established for this structure.
The analysis for sliding on the founda-
tion indicated that the allowable sliding
factor (ratio of total horizontal forces
to total vertical forces) of 0.7 is
exceeded by as much as 57 percent. This
is offset by the high values of the shear
friction factor of safety for this struc-
ture, in excess of 17 compared to minimum
allowable for seismic loading of 3.25.
389
GENERAL
LOCATION
EDWARD HYATT
POWERPLANT
(UNDERGROUND)
Fi gure II
Location Map, Edward Hyatt Powerplant Facilities
390
Figure 190. Fish Barrier Dam
391
392
393
-i! SUTT&R-BUTTE^ ; ILARKIN Vi
oil CAMAL OUTLET I ^ROAD j j
':^
Figure 193. Location Map, Thermal ito Powerplant, Forebay, and Afterbay
394
Recommendation for Seismic Reanalysis
The Department recommended using a pseu-
dostatic analysis and a seismic coeffi-
cient of 0,25 to reanalyze the secondary
structures, in lieu of the rigorous
dynamic analysis used for the critical
structures. The chairman of the Earth-
quake Consulting Board concurred with
this recommendation.
A quick check using the pseudostatic
analysis and a seismic coefficient of
0.25 and 0.6 indicated a minimum shear
friction factor of safety in excess of 9.
A brief study of the consequences of
failure of this structure indicates the
following:
1. Possible loss of life would be
limited to fishermen along the river
_ at the time of the event. This
f' would be further limited to those
fishermen to close to the dam to be
warned.
2. Property damage would be minor and
would be less than that caused by
the Standard Project Flood.
3. Loss of the dam would have little
effect on operation of the project
until repaired or replaced. Complete
loss of the dam would have an effect
on the operation of the fish
facilities.
On the basis of the preceding analysis ,
the Department has determined that no
additional seismic analysis is recommended
for the Fish Barrier Dam.
Power and Pumping Plant Facilities
Edward Hyatt Powerplant
The Edward Hyatt Powerplant is an under-
ground, hydroelectric, pumping-generating
facility located on the Feather River
approximately 5 miles northeast of the
City of Oroville, Butte County.
The powerhouse chamber, located in the
left abutment near the axis of Oroville
Dam (Figure 189) , was excavated in a
metavolcanic rock formation that is pre-
dominately amphibolite. The rock was
fresh and three prominent joint sets
imparted a certain blockiness to it, but
the individual joints were generally
tight .
Since much of the powerhouse is placed
against the rock, (Figure 194) , it can
be assumed that it will experience peak
ground acceleration (PGA) with negligible
magnification. The powerhouse substruc-
ture is a rigid, massive, reinforced
concrete structure which should exper-
ience little or no distress from the
designated load factor.
As a result of the DWR Earthquake Hazard
Committee inspection of the facility,
minor modifications consisting princi-
pally of installations of additional
holddown bolt anchorages and bracing
were made to increase earthquake resis-
tance of unit control centers, emergency
equipment, spare parts storage shelves,
CO2 cylinder racks , and numerous other
items. Items in the power plant still
to be investigated are the anchorages
that fasten the precast wall panels to
the columns; and the columns themselves,
which rest on the generator floor, Ele-
vation 252.0 (Figure 195) . The panels
will most likely experience a higher
response acceleration factor since their
mode of vibration will be considerably
different from that of the main struc-
ture. A pseudostatic analysis using a
peak ground acceleration of 0.25g will
be used to investigate the powerhouse
components . This work is scheduled to
be completed during the 1978-79 fiscal
year.
It was determined that the intake struc-
ture to the powerhouse (Figure 196) was
structurally stable; however, additional
anchorages were installed for a number
of items, the most important of which
are the crane trolleys on the shutter
gantry crane. Holddowns are required
for the trolleys when the crane is not
in operation to keep them on the track
during seismic events.
395
Hi:
4F
Is
1r
396
Figure 196. Overall View of Edward Hyatt Powerplant Intake Structure
398
Conclusion
The powerhouse substructure has been
reviewed using a comparative pseudo-
static analysis of previously designed
powerhouse substructures. Based on
this comparison, it has been determined
that this substructure would be capable
of resisting the forces induced by a
0.25g peak ground acceleration, therefore
no modifications are required.
Modifications will be made to improve
the seismic resistance of powerhouse
superstructure components as necessary.
Thermalito Powerplant
Thermalito Powerplant is a pumping-
generating facility located approximately
4 miles west of the City of Oroville,
Butte County (Figure 193) . The power
plant substructure (Figure 197) is
keyed into a basalt formation, and its
foundation lies on an interflow mater-
ial consisting of basalt breccia in a
matrix of amorphous material. The
plant substructure is a rigid, massive,
reinforced concrete structure which
should move with the basaltic rock
formation and thus experience peak
ground acceleration (0.25g) with little
or no magnification.
This facility was also inspected for
earthquake hazards, and modifications
similar to those at the Edward Hyatt
Powerplant were made.
Items still to be investigated are the
rigid steel frames that form the super-
structure, and the precast concrete
panels and the anchorages that fasten
them to the superstructure (Figure 198) .
This work is scheduled to be completed
during the 1978-79 fiscal year. Above
elevation 165.0, the superstructure
will vibrate in a lower mode of vibration
than the substructure and therefore
experience a somewhat higher response
acceleration factor than the 0.25g
assigned to the substructure.
Conclusion
The powerhouse substructure has been
reviewed using a comparative pseudo-
static analysis of previously designed
powerhouse substructures. Based on
this comparison, it has been determined
that this substructure would be capable
of resisting the forces induced by a
0.25g peak ground acceleration, there-
fore no modifications are required.
Modifications will be made to improve
the Sjeismic resistance of powerhouse
superstructure components as necessary.
399
400
ap i
n
HO i
^M^JL? IHi
Q
I*
401
Miscellaneous Structures
The miscellaneous structures inspected by the DWR Earthquake
Hazard Committee include those listed below:
Oroville Operations and Maintenance Center
Miscellaneous Structures
1. Administration and Maintenance Center
2. General Maintenance Headquarters Building
3. Plant Maintenance Shops
4. Mobile Equipment Repair Building
5. General Maintenance Warehouse
6. Vehicle Storage Building
Oroville Dam Miscellaneous Structures
1. Palermo Outlet Works Control House
2. Instrument Vault
3. Reservoir Gage Station
Thermalito Forebay and Afterbay Miscellaneous Structures
1. Heavy Equipment Building
2. Western Canal and Richvale Canal Outlet Control Building
3. PG&E Lateral Outlet Control Building
4. Sutter Buttes Canal Outlet Control Building
5. Feather River Outlet Control Building
6. Feather River Outlet Control Station
Feather River Fish Hatchery Miscellaneous Structure
1. Maintenance Office Building
2. Hatchery-Spawning Building
3. Ultraviolet Treatment Building
As a result of the earthquake hazard inspection, additional anchor-
ages have been installed for much of the operational equipment in these
facilities.
402
I Conclusion
Damage that may occur to the miscellan-
eous structures is not considered to be
a threat to public safety and property.
For the purpose of the seismic reevalua-
tion, these structures are classified
as noncritical.
i Bridges
Public bridges in the Oroville area were
inspected by the Department of Transpor-
tation following the August 1, 1975,
Oroville earthquake. Fourteen bridges
in the general area showed evidence of
movement, minor damage, or both.
If these bridges were to experience a
peak ground acceleration of 0.25g, some
of them may sustain greater damage .
Therefore, all project- related bridges
will be analyzed for such a loading
during the 1978-79 fiscal year.
Conclusion
Bridge components that will not sustain
the forces generated by a 0.25g peak
ground acceleration will be modified to
strengthen their seismic resistance.
Switchyard Structures and Apparatus
Switchyards play an important dual role
in hydroelectric power systems . They
collect and distribute generated or
incoming power and protect power and
pumping plants. Unlike many power plant
features, switchyard electrical equip-
ment exhibit only light damping charac-
teristics, are fragile, and have very
little ductility because much of the
supporting systems are porcelain. In
addition, many of the physical structures
take on a "lollipop" type of mass dis-
tribution which is conducive to high
amplification factors during severe
earthquake-induced ground movements.
The two switchyards under investigation
are at the Edward Hyatt and Thermal i to
Powerplants .
The Edward Hyatt Powerplant Switchyard
is located at the downstream toe of the
Oroville Dam on the south bank of the
Feather River, approximately five miles
northeast of the City of Oroville
(Figure 189) .
Thermalito Powerplant Switchyard "W" is
located several hundred feet west of
the power plant, approximately four
miles west of Oroville (Figure 193) .
Both switchyard facilities contain
similar electrical apparatus; therefore,
it will suffice to discuss weaknesses
common to both of them.
The types of equipment in the switch-
yards are:
1. Current transformers
2. Potential transformers
3. Disconnect switches
4. Lightning arresters
5. Line traps
6 . Bus supports
7.
230 kV ATB-6 power circuit
breakers
Since no loss of life is expected due
to failure of equipment within the yard,
the switchyards have been classified as
noncritical facilities. Accordingly,
a peak ground acceleration of 0.25g has
been assigned for this seismic
evaluation .
To determine dynamic characteristics of
switchyard equipment, a testing program
had previously been conducted at other
Department switchyards containing similar
power circuit breakers and structural
support systems. Those tests had
revealed critical frequencies and damping
characteristics .
However, since a loss of certain switch-
yard equipment would create only
403
operational inconveniences and minor
outages, investigation efforts were
directed to the most earthquake prone
and critical equipment in the switch-
yards; the 230 kV ATB-6 power circuit
breakers (Figure 199) .
The fundamental frequency for the circuit
breakers ranged from 2.8 to 3.5 hertz,
depending on the direction of excitation
applied, and damping values ranged from
3.6 percent to 6.4 percent of critical.
Dynamic magnification of about 7 was
observed during the testing, which
means at an acceleration input of 0.25g,
the maximum response acceleration would
be about 1.75g. Further studies indi-
cated that the porcelain supports for
the breaker heads cannot withstand
loads of this magnitude without addi-
tional damping or isolation. M
For the proposed study a newly developed
seismic shock-isolation system will be
tested under one of the power circuit
breakers to determine its capability to
protect the breakers during severe
ground movements. The testing program
is scheduled to be conducted during the
1978-79 fiscal year.
Conclusion
Based on the consideration that failure
of electrical equipment in the Edward
Hyatt or Thermalito Powerplant switch-
yards does not pose a threat to public
safety or property, the switchyards are
classified as noncritical elements of
the Oroville Complex.
Figure 199. 230-KV Power Circuit Breakers
404
CHAPTER IX
CONTINGENCY PLAN FOR SEISMIC EMERGENCIES
rhe purpose of this chapter is to specify
procedures to be followed by the Division
of Operations and Maintenance in reacting
to seismic events, and the process for
returning equipment to pre-earthquake
operating levels.
The discussion outlines (1) organization
and responsibilities for both Headquarters
and Field Division; (2) procedures for
reacting to seismic events, including
notification and response; and (3) proce-
dures returning equipment and facilities
to full operational status, which estab-
lishes the criteria for qualifying opera-
tional readiness.
Organization and Responsibilities
Division Policy
The policy of the Division of Operations
and Maintenance during emergencies will
be as follows:
1. Management and operation of the State
Water Project during emergencies will
be in accordance with the contingency
plan.
2. The primary emphasis will be to pro-
vide all possible support to line
activities.
3. The project facilities and control
centers will continue to be operated
in accordance with the Plan of
Operation.
4. Operation will be on as nearly a
normal basis as possible.
5. The Division Command Post in Sacra-
mento, together with a Command Post
in each of the five field divisions,
if required, will be set up to coordi-
nate activities.
6. A declaration of emergency will be
made by the Director upon recommenda-
tion by the Division Engineer, if
required for the Division to expe-
dite contracts, service agreements,
and purchasing processes.
7. Instructions to cease operation of
facilities, to operate additional
facilities, or to change the plan
of operation shall be made only by
the Division Engineer or by the per-
son in charge of the Division Com-
mand Post, after consultation with
the Director, except in emergencies
where immediate action is required.
Division Plan of Operation
Should an emergency occur, the Operations
Control Branch will prepare, distribute,
and implement a Plan of Operation appro-
priate to the situation. The Oroville
power facilities will be kept in opera-
tion by all feasible means .
Where possible, the pumping and genera-
ting units will be operated on a contin-
uous basis to minimize manpower require-
ments on start-up and shutdown, to
lessen chances of shutdown.
Priority will be given to continuing the
operation at the Hyatt Powerplant should
circumstances require discontinuing opera-
tion of the Thermalito facilities.
Oroville Field Division Command Post
On determination of a seismic emergency,
the Field Division Chief, upon direction
or at this discretion, will establish a
Command Post to be manned 24 hours per
day to assure continuous communication
with the Division Command Post.
The chain of command will not change
because of emergency conditions. While
the urgency of the moment may necessi-
tate shortcuts in lines of communications
and activities, every effort will be
made, as time permits, to backtrack and
reestablish that chain.
405
Every effort shall be made to maintain
the normal channel of communication
between the field and headquarters for
the dissemination of operating orders,
condition reports, and forecasts.
The Oroville Field Division has estab-
lished two command posts; one is desig-
nated "Operational", which is the
Master Command Post, and the other is
designated as the "Security Command
Post".
Operational Command Post. The Opera-
tional Command Post will be the respon-
sibility of the Operations Superinten-
dent under the authority of the Field
Division Chief. He will have the
responsibility to meet the Plan of
Operation for water and power deliveries.
1. Operational Facilities. To the
extent possible, the following
facilities in the Oroville Field
Division will remain operational
for the duration of any emergency:
Area Control Center
Command Post - Operational
Edward Hyatt Powerplant
Thermalito Powerplant
All Hydraulic Structures
2. Operational Plan. The above facil-
ities will be operated and main-
tained on as nearly a normal basis
as possible and in accordance with
existing power and water delivery
schedules. The Operations Super-
intendent or his designee shall
keep the Project Operations Con-
trol Center advised of all conditions
relative to the operation of the
Project.
If for any reason, communication links
between the Oroville Operations Command
Post and Project Operations Command
Center are severed, the Operations
Command Post shall maintain the same
operating status that prevailed prior
to the loss of communications. Any
deviations from this procedure must be
authorized by the Operations Superin-
tendent or his designee.
Security Command Post. The Security
Command Post will be the responsibility
of the Chief of the Civil Maintenance
Section under the authority of the Field
Division Chief.
1. The Security Plan. The Security
Command Post Manager will:
(a) direct and monitor Project
facility inspections of civil
features;
(b) recommend to the Field Divi-
sion Chief operational devia-
tions when warranted due to
detectable threats to the
integrity of Project structures;
and
(c) maintain a log of damage and
establish priorities for repair
work.
The Security Plan involves two actions:
Surveillance and Corrective Response.
Surveillance is defined as efforts
expanded toward knowing what is happen-
ing project wide. Corrective response
is defined as efforts expended toward
maintaining integrity or restoration of
facilities.
Procedures for Reacting
To Seismic Events
Oroville Field Division
Detection
Seismic events are detected either by
personal senses in the Field or by instn
mentation response in the Earthquake
Engineering Section in Sacramento.
Earthquake Magnitude and Epicenters
Accurate earthquake magnitude and hypo-
center are determined and reported by
406
the Earthquake Engineering Section in
Sacramento, normally well beyond the
time required to help determine the need
for Project inspections. Preliminary
estimates of magnitudes above 4 . 0 are
made by the Project Operations Control
Center and generally reported to the ACC
within 30 minutes after the event.
This information is helpful but not
complete enough to determine the need
for inspection.
Criteria for Notification
When an earthquake exceeding an estimated
magnitude of 3.0 Richter Scale is felt or
reported with 25 kilometres (15.5 miles)
of the Oroville Seismic Reporting Sta-
tion, the Area Control Center shall
notify the Surveillance Unit Chief, the
State Police Mobile Unit on duty, and
the Project Operations Control Center.
When an earthquake is felt or reported
in excess of an estimated magnitude 4.0
Richter Scale, within 50 kilometres
(31 miles) of the reporting station, the
Area Control Center shall additionally
notify the Civil Maintenance Section
Chief.
Within the near future, peak accelera-
tion values measured in the foundation
and crest of Oroville Dam will be dis-
played in the Area Control Center on
the Data Acquisition Panel. At that
time, O.lOg recorded at the base of
Oroville Dam will replace the* 3.0 Richter
Scale criteria for notification, and
0.15g will replace the 4.0 Richter Scale
criteria.
Response
1. When an earthquake estimated in
excess of magnitude 3.0 Richter
Scale occurs, or the acceleration
values are in excess of O.lOg:
(a) Water and Power Operations
shall continue to operate
under routine constraints.
(b) The Surveillance Unit Chief
shall determine that seismic
instrumentation is functioning
and ready to record a subse-
quent event, and gather and
record certain data in accor-
dance with prescribed standing
instructions.
(c) The State Police mobile unit on
duty will perform a general
inspection of the Project in
accordance with prescribed
standing instructions.
When an earthquake exceeding an
estimated magnitude 4.5 Richter
Scale occurs, or with the determina-
tion that peak accelerations exceed-
ing 0.15g have occurred at the base
of Oroville Dam:
(a) Water and Power Operations
shall continue at the operating
level resulting from a seismic
event. For instance, if four
units are on line when the event
occurs and only two units remain
on line , water and power oper-
ations shall remain in that
configuration until either:
(1) standard operating proce-
dures dictate a change, or (2)
an inspection reveals that it
is safe to continue or to
increase/decrease operations.
(b) The Security Command Post shall
be activated by the Civil Main-
tenance Section Chief at his
discretion to an estimated mag-
nitude 5.0, he may call the
necessary personnel for an
inspection. At an estimated
magnitude 5.0, the complete
Rapid Response inspection is
mandatory. The ACC shall be
advised when the Security Command
Post is activated and when a
Rapid Response Inspection has
been initiated.
407
Inspection of Project Facilities
Following an Earthquake
Significant seismic events are presumed
to precede additional seismic events.
Until enough time has elapsed to perceive
a decay in the frequency and magnitude
of shocks, inspection and investigations
will continue in order to assure that
structures have not been weakened to a
point approaching failure.
Inspections are categorized two ways:
Rapid Response and Follow-up or Final.
1. The Rapid Response Inspection Plan
is a method to immediately determine
that problems may or may not be
developing projectwide. It is a
means for the Field Division Chief
to determine whether corrective
action should be initiated and to
what degree follow-up inspections
are required.
(a) Operational Command Post. The
Operations Section is obligated
to comply with Operational Pro-
cedures (OP series of instruc-
tions) that specifically outline
the inspection and safe operation
of plant equipment. In addition,
the Area Control Center has on
its Status Display boards, indi-
cators of water and power condi-
tions of the overall Project
Features. Rapid inspection and
response therefore are well
outlined.
(b) Security Command Post. The area
of responsibility of the Security
Command Post is divided geograph-
ically and assigned to three
inspection teams. (See Schematic
Diagram of Oroville Complex
Figure 200) .
(1) Oroville Dam and vicinity
(2) Thermalito Forebay and
vicinity
(3) Thermalito Afterbay and
vicinity
Detailed instructions of routes to fol-
low and items to inspect are provided
for each team. In addition a training
film has been prepared that defines the
plan of inspection, shows the order of
inspection, the types of damage to look
for in each geographical area, and
specifies the procedure to be used in
reporting damage and conditions.
The surveillance crew, within all these
geographical areas, attends seismic and
performance instrximentation.
2. The follow-up Inspection Plan is
developed as information becomes
available. In some cases visual
inspections may be adequate. Gen-
erally, when accelerations of less
than 0.15g are experienced in Oro-
ville Dam, follow-up inspections
will not be required. Damage reports
will be filled out for all abnormal-
ities to civil features discovered
during inspections. Damage reports
will serve to identify large or
small problems and to initiate Job
Requests or Job Orders as may be
determined by review and verifica-
tion of the Security Command Post
Manager .
Returning Facilities and Equipment
To Full Operation Status
The following pages are lists of all
operational facilities and features in
the Oroville Complex, starting with Lake
Oroville, moving downstream, and ending
with the Thermalito Afterbay ground water
pumping system.
The primary features of concern in the
Lists of Operating Criteria are the four
bodies of water that can be regulated in
the Oroville Complex which are :
Lake Oroville (Page 414) See Figure 201
Thermalito Diversion
(Page 417) see Figure 202
Thermalito Forebay
Reservoir (Page 418) See Figure 202
Thermalito Afterbay
Reservoir (Page 420) See Figure 203.
408
Regulating Feature
The features that can be regulated have
a normal operating criteria, and cui
emergency operating condition. The
emergency condition is dictated by the
degree, or potential degree, of loss of
structural integrity. The listed cri-
teria is mandatory and must be met,
either on an interim basis while investi-
gations continue, or as assurances of
integrity come in from either field or
plant investigations . Many of the
criteria conditions can be determined
quickly, whereas others take time and
testing for full assurance that they
are validly met.
Nonregulating Features
Nonregulating features are those struc-
tures that cannot be operated, such as
Oroville Dam or the Thermalito power
canal. Certain conditions as are
described after each nonregulating
feature constitute a declaration of true
emergency for that feature. Water and
power operations or both then become
secondary to whatever response is
required to protect lives or reduce
further damage.
409
OROVILLE DAM S VICINITY
SUTTER BUTTE OUTLET
THERMALITO
AFTERBAY
Figure '200. Schematic Diagram of Oroville Complex
410
OROVILLE DAM AND VICINITY
LAKE OROVILLE
WATER FLOW
PATH 1
A
^ L
^
^
REGULATING
FEATURES
NONREGULATING
FEATURES
^
1
^
1
1
r
i
i
y
1
PALERMO
OUTLET
FLOOD
CONTROL
SPILLWAY
RIVER OUTLET
SPHERE VALVES
HYATT INTAKE
SHUTTERS
OROVILLE
DAM
u
1
PARISH CAMP
SADDLE DAM
1
r
^r
1
1
1
EXPORT
HOWELL
BUNGER
VALVES
INTAKE
GATES
BIDWELL
CANYON
SADDLE DAM
-L
EMERGENCY
SPILLWAY
/
/
^
HYATT
POWER PLANT
¥■
r
^
r
y
TAP GUARD
VALVES
TURBINE
SHUT-OFF
VALVES
^
r
WICKET
GATES
iV
w
UNITS
■
1
f
1
f
1
CONDENSING
GENERATING
PUMP BACK
^
A
\.
k
THERMALITO DIVERSION
POOL
▼
i
L
L EG END
Figure 201. Schematic Diagram of Oroville Dam and Vicinity
411
THERMALITO FOREBAY AND VICINITY
RADIAL GATES
BYPASS GATE
CONDENSING
THERMALITO DIVERSION
POOL
WATER FLOW PATH
REGULATING
FEATURES
DIVERSION DAM
RELEASE
FEATURES
HOWELL
BUNGER
VALVE
FEATHER
RIVER
REGULATING
FEATURES
THERMALITO
INTAKE
THERMALITO
POWER PLANT
WICKET GATES
GENERATING
FISH
HATCHERY
NONREGULATING
FEATURES
THERMALITO
DIVERSION
DAM
POWER CANAL
RADIAL GATES
I A
POWER
CANAL
THERMALITO FOREBAY
RESERVOIR
NONREGULATING
FEATURES
THERMALITO
INTAKE
STRUCTURE
POWER
CANAL
TL.
THERMALITO
FOREBAY
DAM
PUMP BACK
*~
L EG END
WATER FLOW PATH
TAIL
CHANNEL
THERMALITO AFTERBAY
RESERVOIR
Figure 202. Schematic Diagram of Thermal i to Forebay and Vicinity
412
THERMALITO AFTERBAY AND VICINITY
THERMALITO AFTERBAY
RESERVOIR
:*n
WATER FLOW PATH
REGULATING
FEATURES
RIVER
OUTLET
GATES
SUTTER
BUTTE
GATES
PGSE
GATES
FEATHER
RIVER
NONREGULATING
FEATURES
GROUND WATER
PUMP SYSTEM
WESTERN
RICHVALE
GATES
THERMALITO
AFTERBAY
DAM
LEGEND
^ WATER FLOW PATH
Figure 203- Schematic Diagram of Thermal ito Afterbay and Vicinity
413
LIST OF OPERATING CRITERIA FOR REGULATING LAKE OROVILLE
DECISION MAKING CRITERIA FOR OPERATING FEATURES WHICH CAN BE REGULATED
A. PALERMO OUTLET
1. 30-inch butterfly valve {1 valve)
a. Must be closed when fixed dispersion cone valve
integrity is questionable.
b. Must be closed when Palermo intake works integrity is
questionable.
c. Must be open to meet water delivery demand by Oroville
Wyandotte Irrigation District.
2. 12-inch fixed dispersion cone valve (1 valve)
a. Must be closed when 30-inch butterfly valve integrity
is questionable.
b. Must be closed for Palermo Canal failure.
c. Must be open to meet water delivery demand by
Oroville Wyandotte Irrigation District.
B. OROVILLE DAM SPILLWAY
1. Radial gates (8 gates)
a. Must be available for maintenance of the flood
control reservation.
b. Must be available for Lake Oroville regulation.
C. RIVER OUTLET VALVES
1. Spherical valves (2 valves)
a. Must be closed when Howell Bunger valves integrity
questionable.
b. Must be closed when intake integrity is questionable.
c. Must be open when Howell Bunger valves will be
operated .
d. Should be closed when Howell Bunger valves are not
needed.
2. Howell Bunger valves (2 valves)
a. Must be closed when diversion tunnel No. 2 has
severe blockage.
b. Must be closed when spherical valve integrity is
questionable.
c. Must be opened when water delivery is unavailable
thru Hyatt Powerplant.
414
D. EDWARD HYATT INTAKE
1. Intake gates (2 gates)
a. Must be closed during a powerhouse disaster.
b. Must be closed for Penstock, turbine shutoff valve
or tap guard valve damage.
c. Must be open to meet Edward Hyatt Powerplant water
demand .
2. Shutters (26 shutters)
a. Enough must be removed in order to comply with
Shutter Submergence Criteria.
b. Enough must be in place in order to control the
temperature of water releases.
c. Enough should be in place to provide protection
from debris at lower levels.
E. EDWARD HYATT POWERPLANT
1. Turbine shutoff valves (6 valves)
a. Must be closed if powerplant is flooded.
b. Must be closed if penstock integrity is questionable.
c. Must be open for unit operational demand.
d. Should be open to control auto oscillation,
e. Should be closed if tailrace tunnel is blocked.
f . May be open if intake gates are closed.
2. Tap guard valves (6 valves)
a. Must be open for raw and cooling water supply to Edward
Hyatt Powerplant units .
b. Must be closed for failure of cooling water line
below the valves.
c. Should be closed in the event of powerplant flooding.
3. Wicket gates (6 gate sets)
a. Must be open if units are generating or pxomping.
b. Must be closed for synchronous condensing.
c. May be closed for unit shut down.
d. May be closed for testing purposes of sediment bearing
water appearing in the tailrace tunnel.
4. Unit operation- synchronous condensing (6 units)
a. Cannot be done if units are generating or pumping.
b. May be done for power system stability (as requested
by the power company.)
415
5. Unit operation-generating (6 units)
a. Cannot be done if intake gates are closed.
b. Cannot be done if powerplant disaster exists.
c. Must not be done if unit integrity is questionable.
d. Must not be done if an incompatible stage differential
exists between Lake Oroville and Thermalito Diversion
Pool.
e. Cannot be done if units are pumping or synchronous con-
densing.
f. May be done to provide station service. (units 1 or 4).
g. Must not be done if tailrace tunnels are blocked.
h. Should not be done if switchyard or transmission line integrity
are not OK.
i. Should not be done if no power or water demands exist,
j . Should be done if regulation of Lake Oroville is
required.
6. Unit operation-pump back (3 units)
a. Cannot be done if intake gates are closed.
b. Cannot be done if powerplant disaster exists.
c. Must not be done if unit integrity is questionable.
d. Must not be done if an incompatible stage differential
exists between the Thermalito Diversion Pool and Lake
Oroville.
e. Cannot be done if units are synchronous condensing or
generating.
f. Must not be done if switchyard or transmission lines
are not OK.
g. Should not be done if tailrace tunnel is blocked,
h. Should be done at the power company request.
i. Should be done for water conservation.
j. May be done for Diversion Pool regulation.
II. CRITICAL CONDITIONS FOR FEATURES WHICH CANNOT BE REGULATED
A. OROVILLE DAM
1. Uncontrollable water born sediment passing thru embankment,
groins, foxindation, grout gallery or tailrace tunnel.
2. Significant slips or cracks in embankment.
3. Crest settlement which could lead to overtopping.
4. Significant vertical or horizontal displacement.
5. Excessive increases in pore pressure.
B. BIDWELL CANYON SADDLE DAM
1. Uncontrollable water born sediment thru embankment, groins
or foundation.
2. Significant slips or cracks in embankment.
3. Crest settlement which could lead to overtopping.
4. Significant vertical or horizontal displacement.
416
C. PARISH CAMP SADDLE DAM
1. Uncontrollable water born sediment thru embankment, groins
or foundation.
2. Significant slips or cracks in embankment.
3. Crest settlement which could lead to overtopping.
4. Significant vertical or horizontal displacement.
D. OROVILLE DAM SPILLWAY
1. Extraordinary damage to concrete monoliths or groins.
2. Inoperable radial gates limit ability to maintain flood
control reservation.
E. EDWARD HYATT INTAKE AND PENSTOCK
1. Extraordinary damage to structure, trash racks, emergency
gates, or penstocks.
F. PALERMO INTAKE AND OUTLET
1. Loss of control of water thru outlet.
G. RIVER OUTLET VALVE CHAMBER
1. Loss of control of water thru outlet.
2 . Extraordinary damage to tunnel plugs .
LIST OF OPERATING CRITERIA FOR REGULATING
THERMALITO DIVERSION POOL
DECISION MAKING CRITERIA FOR OPERATING REGULATING FEATURES
A. THERMALITO DIVERSION DAM
1. Radial gates (14 gates)
a. Must be open to pass flood control waters to
Feather River.
b. Should be operable to regulate waters in Thermalito
Diversion Pool and Thermalito Forebay.
c. Should be closed for Thermalito Powerplant operations.
d. May be used to meet water delivery commitments in the
Feather River.
2. Howell Bunger valve (1 valve)
a. Should be open to maintain minimum water release
for stream flow maintenance in the Feather River.
3. Fish hatchery valve (1 valve)
a. Should be open to meet water demand from the
Feather River Fish Hatchery.
417
4, Radial gates to power canal (3 gates)
a. Must be closed to protect the Thermalito Power Canal
and Thermalito Forebay during extreme flood control
conditions in Thermalito Diversion Pool.
b. Must be open to keep Thermalito Powerplant operational.
c. May be closed if Thermalito Power Canal or Thermalito
Forebay Dam integrity is questionable.
II. CRITICAL CONDITIONS FOR FEATURES WHICH CANNOT BE REGULATED
A. THERMALITO DIVERSION DAM
1. If uncontrollable water born sediments are passing thru
the groins or foundation.
B. THERMALITO POWER CANAL HEADWORKS
1. Extraordinary damage to radial gates.
LIST OF OPERATING CRITERIA FOR REGULATING THERMALITO FOREBAY
RESERVOIR AND POWER CANAL
I. DECISION MAKING CRITERIA FOR OPERATING REGULATING FEATURES
A. THERMALITO INTAKE STRUCTURE
1. Bypass gate (1 gate)
a. May be open when Thermalito Powerplant is not
operational .
b. May be used for Thermalito Afterbay regulation.
c. May be used for Thermalito Forebay regulation.
2. Fixed wheel gates (2 gates)
a. Must be used for uncontrollable water thru units.
b. Should be used for penstock rupture.
B. THERMALITO POWERPLANT
1. Wicket gates (4 gate sets)
a. Must be open if units are generating or pumping.
b. Must be closed for synchronous condensing.
c. May be closed for unit shut down.
2- Unit operation-synchronous condensing (4 units)
a. Cannot be done if units are generating or pximping.
b. May be done for power system stability (as requested
by the power company) .
418
Unit operation-generating (4 units)
Cannot be done if fixed wheel gates are closed.
Cannot be done if a powerplant disaster exists.
Must not be done if unit integrity is questionable.
Must not be done if an incompatible stage differential
exists between the Thermalito Forebay and the
Thermalito Tail Channel.
Cannot be done if units are pumping or synchronous
condensing.
Must not be done if tail channel is blocked.
Should not be done if switchyard or transmission
line integrity are not OK.
Should not be done if there are no power or water
demands .
May be done for regulation of Thermalito Forebay or
Thermalito Afterbay.
May be done to provide station service.
4. Unit operation-pumpback (3 units)
b.
Cannot be done if fixed wheel gates are closed.
Cannot be done if powerplant disaster exists.
Must not be done if unit integrity is questionable.
Must not be done if an incompatible stage differential
exists between the Thermalito Forebay and the
Thermalito Tail Channel.
Cannot be done if units are synchronous condensing
or generating.
Must not be done if switchyard or transmission
lines are not OK.
Should not be done if tail channel is blocked.
Should be done at the power company request.
Should be done for water conservation.
May be done for Thermalito Afterbay or Thermalito
Forebay regulation.
II. CRITICAL CONDITIONS FOR FEATURES WHICH CANNOT BE REGULATED
A. THERMALITO FOREBAY DAM
1. If uncontrollable water born sediments are passing thru
the embankment, groins or fovindation.
2. Significant slips or cracks in embankment.
3. Crest settlement which could lead to overtopping.
4. Significant vertical or horizontal displacement.
B. THERMALITO INTAKE STRUCTURE
1. Uncontrollable water passing thru or under intake structure.
2. Extraordinary damage to structure, trash racks or bypass
gate.
3. Extraordinary damage to end wall gravity dam.
419
C. THERMALITO POWER CANAL (Cut Section)
1. Extraordinary damage to canal cut or lining.
D. THERMALITO POWER CANAL (Fill Section)
1. If uncontrollable water born sediments are passing thru
the embankment, groins, or founiation
2. Significant slips or cracks in embankment.
3. Crest settlement which could lead to overtopping.
4. Significant vertical or horizontal displacement.
LIST OF OPERATING CRITERIA FOR REGULATING
THERMALITO AFTERBAY RESERVOIR
DECISION MAKING CRITERIA FOR OPERATING REGULATING FEATURES
A. THERMALITO AFTERBAY RIVER OUTLET
1. Radial gates (5 gates)
a. Should be open to meet Feather River stream flow
maintenance commitments.
b. May be open to regulate Thermalito Afterbay
Reservoir.
B. SUTTER- BUTTE OUTLET
1. Slide gates (4 gates)
a. Must be open to meet Sutter-Butte Irrigation
District water demands .
C. PG&E OUTLET
1. Slide gates (1 gate)
a. Must be open to meet PG&E water demands.
D. WESTERN CANAL AND RICHVALE OUTLETS
1. Slide gates (8 gates)
a. Must be open to meet Western Canal (PG&E) or
Richvale Irrigation District water demands.
E. THERMALITO AFTERBAY DAM GROUND WATER PUMPING SYSTEM
1. Ground water pumps (15 pumps)
a. Must be on to maintain ground water aquifer level.
b. Must be off to prevent overdraft of ground water
aquifer.
420
II. CRITICAL CONDITIONS FOR FEATURES WHICH CANNOT BE REGULATED
A. THERMALITO AFTERBAY DAM
1. If uncontrollable water born sediments are passing
thru the embankment^ groins^ or foundation.
2. Significant slips or cracks in embankment.
3. Crest settlement which could lead to overtopping.
4. Significant vertical or horizontal displacement.
B. THERMALITO POWERHOUSE STRUCTURE
1. Uncontrollable inflow into Thermalito Tail Channel.
2. Extraordinary damage to Thermalito Powerhouse.
C. THERMALITO AFTERBAY RIVER OUTLET
1. Extraordinary damage to structure or radial gates.
D. SUTTER- BUTTE OUTLET
1. Extraordinary damage to structure.
E. PG&E OUTLET
1, Extraordinary damage to structure.
F. WESTERN-RICHVALE OUTLETS
1. Extraordinary damage to structure.
Commentary
Seismic emergencies at the Oroville Field
Division are addressed through the pre-
ceding contingency plan.
Priorities for inspection and work are
established on the following basis:
1. Attention to those structures whose
failure can lead to loss of life
and significant property damage.
2. Attention to those facilities whose
operation can lead to further damage
or failure to Project structures.
3. Attention to those structures whose
condition may lead to limiting the
ability to meet power and water
delivery commitments .
4. Attention to those structures and
facilities that are supportive to
efficient operation but are not in
themselves, critical to priorities
1, 2, and 3.
Conclusion
The contingency plan is attentive to
established Division Policy; it provides
for detection, notification, and response
to seismic events. The plan also
includes a list of operational facilities
and features along with criteria that
must be met before returning to pre-
earthquake operating status.
421
APPENDIX A
REPORTS PREPARED BY THE SPECIAL CONSULTING BOARD
AND RESPONSES BY THE DEPARTMENT OF WATER RESOURCES
1. Reports of the Consulting Board for Earthquake
Analysis, 11 August 1975 424
2. Report of the Special Consulting Board for the
Oroville Earthquake to Mr. R. B. Robie,
12 September 1975 429
3. Memorandum, "Proposed Department Activities
in Response to Consulting Boards." from
Robert W. James to Mr. Ronald B. Robie,
October 30, 1975 436
4. Report of the Special Consulting Board for the
August 1, 1975 Earthquake to Mr. R. B. Robie,
23 November 1976 444
5. Memorandum, "Proposed Department Activities
in Response to the Special Consulting Board
Meeting of November 22 and 23, 1976," from
Robert B. James to Ronald B. Robie, March 4, 1977 . . 452
423
11 August 1975
REPORT OF THE CONSULTING BOARD FOR
EARTHQUAKE ANALYSIS
Messrs: Robert Jansen
H. G. Dewey, Jr.
Gentlemen :
At a meeting on 8 August 1975 with the Consulting Board for
Earthquake Analysis, staff members of the Department of Water
Resources review^ed the instrumental and other data obtained in the
vicinity of Oroville Dam as a result of the series of moderate
earthquakes which have occurred in that region, and presented
evaluations of the performance of the SWP facilities in response to
the earthquake effects. At the conclusion of the briefing the Board
was asked to respond to questions relating to the earthquakes and
possible future events. Our responses are presented below.
Question 1
The designs of the SWP facilities in the Oroville area were predicated
upon certain appraisals of probable future regional seismicity in the
site vicinities. In view of the recent earthquake activity in the
Oroville area are the original appraisals still valid? What adjustments,
if any, should be made in those appraisals?
la. Although the original appraisal by DWR staff that "the
Oroville dam site is in an area of relatively light seismic activity"
may have been justified by the data available at the time of design
(1958), it should now be modified in the light of the recent earthquake
activity in the Oroville area and of knowledge gained since 1958. In
view of the developments, it is appropriate to consider that earthquakes
ranging up to magnitude 6. 5 may occur within a few miles of the dam
site.
424
Page 2
Question 2
What factors should be examined in determining if recent appearance
of extended seismic activity is related to the 10-year existence of
Oroville Reservoir in the area of activity?
2a. If studies along these lines in other parts of the world
are any indication, investigations of this relationship are likely to be
quite difficult, and even inconclusive. Nevertheless, a number of
sets of observations may throw some light on the matter and it is
essential that they be made soon and as precisely as possible.
a) The DWR should arrange to have repeat geodetic surveys
made of past triangulation nets and, particularly, level lines in the
region of the reservoir and recent earthquake activity. These surveys
should be made as quickly as practicable and perhaps repeated after
a few months.
b) DWR should undertake a timed chemical explosion in a
borehole near the epicenter of the main shock (August 1) while the
majority of field seismographs are still operating in the earthquake
area. Such an explosion is a proven way of calibrating the location
of earthquake foci in the region against a seismic source with known
position. In addition, the calibration explosion will calibrate the
polarity of the seismograph responses thereby enabling more reliable
fault-plane solutions to be computed.
c) It is essential that surface fractures possibly associated
with faulting at depth be carefully delineated and documented without
delay. Low-altitude, low-sun-angle aerial photography may be of
assistance in this effort. It is also critical that the local surficial
geology be more completely mapped and better understood, if surface
faulting has indeed occurred. Two critical questions are: (1) Have
the earthquakes occurred along a pre-existing fault, particularly one
with Quaternary displacement and (2) can the causative fault be traced
425
Page 3
beyond the area of recent earthquakes into areas of future hazard?
In all geological efforts, DWR personnel should coordinate their work
with those of other groups studying the earthquake.
d) Another line of investigation of any connection between the
reservoir and recent earthquake activity depends upon computation
of stresses in crustal models loaded by appropriate surface forces.
Theoretical work along these lines should be supported and evaluated
against the Oroville data.
Question 3
What does the board recommend in the way of immediate and future
seismic data collection? Seismic data evaluation?
a) All instrumental data recorded by DWR in connection with
the Oroville earthquakes should promptly be put into usable form
and published. The significance to the Department and to scientific
and engineering communities cannot be overestimated, and care must
be taken not only to adequately preserve the original records, but
also to reproduce the data in suitably annotated graphic form; and
when appropriate, records should also be digitized. As soon as the
recorded data are in an easily understood form, it is requested that
copies be provided to each Board member.
b) DWR should establish a permanent telemetered seismic
station near the epicenter of the August 1st main shock, and temporary
stations should continue to be operated tn the area as long as significant
aftershock activity lasts. The Department should continue to make
sure that it has portable seismographic units available to move into
critical areas of suspicious seismic activity in California, as it did
several weeks prior to the main Oroville event.
c) DWR should install additional strong -motion accelerographs
in the vicinity of Oroville Dam. There should be two permanent
accelerographs on the crest of the dam and one permanent accelerograph
426
Page 4
on each abutment; and three temporary accelerographs should be
installed in a triangular array in the epicentral region of the August 1975
earthquakes, replacing the Caltech instruments. All these instruments
should be equipped with radio time recording. The two AR 240 accelero-
graphs presently located on the dam and abutment should be removed from
their present locations, renovated and used elsewhere.
d) DWR should review its procedures for reacting to the occurrence
of an earthquake near a dam or other major facility, i. e. , to plan appro-
priate actions for getting additional strong -motion accelerographs, and
other instruments, in the field, checking operability of instruments, etc.
e) The static and dynamic data from instruments in and about the
dam should be processed and put into completely usable form, and then
be used together with current, accepted analysis procedures to evaluate
the dynamic properties of the dam and its materials.
f) The experience gained frona the Oroville earthquakes in sensing
and recording significant physical behavior should now be applied to all
major DWR dams and facilities with a view to improving the collection of
data. This should include installation of new instruments, improving
existing instrumentation, and increasing the reliability of the instrument
systems.
g) DWR should specially review the seismic instrumentation program
at Oroville with experts in instrumentation, in recording and processing
data, making use of the latest knowledge and expertise to improve the system.
h) A survey program of leveling and triangulation of the dann and
adjacent area should be completed as soon as possible, consistent with
accuracy control, etc. In addition, arrangements should be made in colla-
boration with other appropriate agencies to resurvey a more general area and
to tie the surveys together. Comparisons should be made with prior data to
determine if there have been any changes of a differential or of an absolute
nature in the region or the dam. The survey data from the dam and adjacent
points should also be correlated with the measurements from movement
devices in the dam.
427
Page 5
C.R. ALLEN ^^ ^,1^/y^
3jk. BLUME
B.A. BOLT
/ G.W. HOUSj^ER
/
H.B. SEEDf ^
428
12 September 1975
Report of the Special Consulting Board for the Oroville Earthquake to:
Mr. R. B. Robie, Director
Department of Water Resources
At a meeting on September 11 and 12, 1975 with the Special Consulting
Board for the Oroville Earthquake, staff members reviewed information
relevant to the Oroville earthquake and the performance of Oroville dam
and its facilities, and described the proposed seismic reevaluation of the
dams, structures and equipment. At the conclusion of the meeting the
Board was asked to respond to seven questions. Our responses are pre-
sented below.
Question 1
At its meeting on August 8, 1975, the Consulting Board for
Earthquake Analysis advised that the appraisals of the regional
seismicity in the Oroville area be modified and recommended several
specific actions as a part of that reappraisal. What comments and
further suggestions does the Special Consulting Board on the Oroville
Earthquake have with regard to the progress of the Department's im-
plementation of those recommendations?
The Department has responded commendably to the actions recom-
mended on August 8, 1975. A few projects are not yet complete and
these should be carried forward as quickly as feasible. These include
particularly the calibration explosion and the detailed geological
mapping.
As well as the additional strong-motion instrumentation to be in-
stalled at the dam and the improved recording capability there, the
Department should establish water gage stations at several suitable
positions around the reservoir. The purpose of the gages woiild be to
determine if regional tilting of the crust \inder the reservoir, perhaps
related to an impending earthquake, is occurring.
429
Report of the Special Consulting Board for the Oroville Earthquake
page 2
During the presentations it became apparent that some additional
administrative attention needs to be given to the line of responsibility
for continuous maintenance, for emergency operation during earthquakes!
and modernization of monitoring equipment. In particular, it would
seem best if the earthquake engineering group had the responsibility
for ensuring the satisfactory performance of all seismographic instru-
mentation and analysis.
Question 2
What comments does the Board have regarding the performance
of the dams and other structures?
The Board ^was presented v/ith extensive oral and written reports
covering observations of various structures of the Oroville— Thermalito
complex immediately following the Oroville earthquake, and for many of
these structures during the interim since that earthquake. All data
submitted indicate that the related structures performed satisfactorily
without distress or damage, and as anticipated in the design.
The Board commends the Department for its prompt inspection of
project structures following the earthquake.
Question 3
What are the Board's views on the identification of the causative
fault? Is it possible to identify the fatilt beyond the recent epicentral
area?
The Board feels that the causative fault zone has already been
identified with reasonable confidence, although the zone does not neces-
sarily comprise a single fracture surface. Both the seismological and
geological studies strongly suggest failure by normal (extensional)
430
Report of the Special Consulting Board for the Oroville Earthquake
page 3
faulting on a zone trending roughly north, and dipping steeply west.
In all liklihood, the causative fault zone extends farther to the north
and south than the segment broken at depth during this series of
earthquakes, but these extensions have not as yet been positively identi-
fied. It is important that further work to identify these extensions be
vigorously pursued- -by detailed geologic mapping, by continued seis-
mic monitoring, by repeated geodetic surveys across the suspected area,
and by further trenching of suspicious features. Particular attention
should be given to understanding the lineaments identified from aerial
imagery and to searching thoroughly for all possible exposures of faulted
Quaternary strata.
Question 4
What are the Board's recommendations concerning the design
earthquakes proposed for use in the seismic reanalyses of the Oroville-
Thermalito structures?
The Board considers that an appropriate earthquake motion for re-
evaluation of structures critical to public safety in the Oroville—
Thermalito complex would be one producing a peak acceleration of
0.6 g and having characteristics similar to those developed near Pacoima
dam during the San Fernando earthquake of February 9, 1971. The
time-history of such a motion should be obtained from a modified form
of the Pacoima dam record, as discussed in the Report of the Consulting
Board for Earthquake Analysis dated May 22, 1973. The actual time-
history could be the same as that forwarded to Mr. Jansen by Clarence
R. Allen with his letter of January 16, 1974, except that the duration of
shaking should be limited to the first 20 seconds of the record provided,
and all ordinates of the record should be multiplied by a suitable scal-
ing factor to give a peak acceleration of 0.6 g .
431
Report of the Special Consulting Board for the Oroville Earthquake
page 4
In addition the structures should be checked for the motions pro-
duced by the following earthquakes:
(a) a Magnitude 8.5 earthquake occurring at a distance of 100
miles
(b) a Magnitude 7.25 earthquake occurring at a distance of 35
miles
It is tinlikely that these latter two earthquakes will produce conditions
more critical than the motion discussed in detail above, but the check]
should be made to verify that this is so. Design earthquakes for non-
critical structures can be less severe in intensity than those discussec
above and the Board w^ill defer this recommendation until the evaluation
of critical structures is completed.
Question 5
What are the Board's comments concerning the proposed progrcim
for the seismic reanalyses of the Oroville-Thermalito structures?
The Board concurs with the Department's concept of establishing
criteria for the relative priority of reassessing the seismic safety of
the various Oroville-Thermalito structures. It also concurs that those
structures most critical in terms of public safety should be analysed by
the best available dynamic methods. Among these structures the
Board includes both Oroville dam and its Spillway.
In regard to the Thermalito embankment dams, it is suggested
that those two or three sections of the Forebay and Afterbay dams
which appear to be least stable from fo\indation and/or dynamic response
points of view be selected for detailed reevaluation using dynamic analy-
ses procedures. "When these studies have been completed other embank-
ment dams in the Oroville-Thermalito complex might well be reassessed
by judgment without detailed analysis.
432
Report of the Special Consulting Board for the Oroville Earthquake
page 5
In regard to the many reinforced concrete structures in the complex,
only those that can be shown to be critical to public safety would seem
to justify the use of sophisticated dynamic analysis procedures, but all
structures evaluated in the original design of the project should be
checked for adequacy either by judgment procedures or by testing their
adequacy under increased assximed earthquake loading.
Question 6
The Board is requested to provide further explanation and gui-
dance concerning the Earthquake Analysis Board's recommendation {2d)
to evaluate stresses in crustal models.
The Board has no further recommendations at this time. Upon
completion of the crustal stress analyses no^v being made by others,
the Departanent may wish to review the question again.
Question 7
Does the Board have any other comments or recommendations?
The Board offers the following suggestions, some of v/hich con-
stitute reinforcement of procedures discussed previously or in-process,
(a) The Department should take full advantage of data collected or
developed by all other agencies, both public and private, con-
cerned with the Oroville area seismicity. Cooperation with
such agencies and exchange of data would ensure that all
reliable data are made available toward the solution of the
problem.
(b) The Department should develop a detailed procedure for the
proposed seismic stability evaluation of Oroville dam embank-
ment, with particular definition of the steps planned for
433
Report of the Special Consulting Board for the Oroville Earthquake
page 6
determining the dynamic strength properties of the various
embankment materials under eonfi-ning pressures of up to 500
psi.
(c) The Department should review procedures and contingency plans
at all dams and major installations for returning equipment and
facilities to full service after a shutdown due to an earthquake.
Directives for return of eqmpment to preearthquake operating
levels should be based upon full knowledge of project conditions
in order to avoid premature start-up and potential extension
damage.
(d) In vie'w of recent press reports concerning the alleged likelihood
of future large earthquakes near Oroville, the Special Board empha-
sizes that the hypothetical maximum earthquake of Magnitude 6.5
mentioned in the Earthquake Board's report of 1 1 August 1975 is
considered to be a very \mlikely event and is intended to be used
for safety review. Furthermore, it is our judgment that any
earthquake significantly stronger than the Magnitude 5«i7 event
of 1 August 1975 is improbable in the near future.
434
Respectfully Submitted,
J.AA y
C. R. Allen
JohA A. Blume
c pr.< >< ><^t/a?.
Bruce A. Bolt
Wallace L. Chadwick
eorge W. Housner
T. M. Lejfe
Alan L. O'Neill
lilip (3/ Rutledge /
H. Bolton See'd'
435
£tate of California
Memorandum
The Resources Agenl|
To : Mr. Ronald B. Robie
Robert W. James
From Department of Water Resources
Date : OCT 3 0 1975
File No.:
Subject: Oroville Earthquakj
of August 1975, Proposed
Department Activities in
Response to Consulting
Boards
As requested by your August 22, 1975 memorandum, presented below
is a description of our program to implement the recommendations
made by the Consulting Board for Earthquake Analysis in their
August 8, 1975 report and by the Special Board for the Oroville
Earthquake in their September 12, 1975 report. An estimate of
cost for carrying out these activities is also included. This
memorandum will also satisfy the requirements of Water Resources
Eiigineering Memoreindum No. 23 by accounting for the actions taken
to the Boards' conclusions and recommendations.
The items below are listed by number as they appear in the Board
reports. Copies of the reports are attached for easy reference.
Consulting Board for Earthquake Analysis
la.
The level of seismic activity in the Oroville area will be
reappraised. Accelerograms will be developed for earthquakes
that are considered to be credible. Included will be a
local earthquake with Magnitude 6.5 as recommended by the
Board and a Magnitude 8+ on the San Andreas fault. Finite
element analyses will be conducted on Oroville Dam using
one or more of the strongest accelerograms. These analyses
will be carried out by personnel of the Division of Safety
of Dams who presently have the expertise. Dr. H. B. Seed
will be retained throughout the study to provide guidance.
Additional soils testing, under the direction of Dr. Seed,
will be conducted at the Richmond Laboratory. The Division
of Design and Construction will fund the entire study and
will have overall responsibility for its completion and
final report. Dr. Seed has been contacted, and he generally
agrees to this approach.
The accelerograms will be examined to determine if the seismic
factors used for the design of other major structures in the
Oroville-Thermalito Complex are still considered adequate.
Structures will be reanalyzed as necessary. The manpower
shown is tentative as it will depend upon early staff findings,
Staff time 2.5 man years
Laboratory soil testing
$ 82,000
20, 000
$102,000
A36
Mr. Ronald B. Robie -2- OCT 30 1975
Five survey parties, two from the Division of Operations
and Maintenance, two from the Division of Land and Right
of Way, and one crew from the U. S. Geological Survey
were involved in the work in the Oroville area. Coordination
was provided by Division of O&M, Chief of Precise Surveys.
Principal objectives .that have been achieved include: (a)
vertical suid horizontal surveys of Oroville Dam, (b) level
rtins over previously established lines to attempt to deter-
mine location of major faults, (c) a survey of the horizontal
and vertical control network about Lake Oroville, (d) a survey
of the epicentral area of the earthquake with a tie to
established bench marks outside the affected area, (this
work was done by U.S.G.S.), and (e) surveys of the smaller
structures in the Oroville-Thermalito Complex.
The U.S.G.S. survey party operated at its own expense.
Department survey cost (including
travel expenses) $ 55,000
The calibration explosion is being coordinated with U.S.G.S.
Because CWR equipment could be made available before U.S.G.S.
equipment, the recommended shot was undertaken by this
Department. The plan involves one drill hole with the
explosion at a depth of about 300 feet. Drilling is now
under way, and is expected to be completed before October 17.
The hole will be loaded and shot as soon thereafter as
possible.
Aside from the shot recommended by the Consulting Board,
the U.S.G.S. has proposed to cooperate in staging two
additional shots - one in the Yuba River near Marysville
and another in one of the northern arms of Lake Oroville.
These shots would supplement the Department shot and would
more precisely define the crustal structure in the Oroville
region.
Cost of DWR shot: drilling, materials
staff time $ 40,000
A search for the fault that caused the earthquake revealed
a cracked zone along an old fault south of Wyandotte. It
is believed this is the fault, or one of the faults, related
to the recent seismic activity. Remote sensing imagery
consisting of U-2 infrared color, ERTS satellite and side-
looking airborne Radar (SLAR) imagery were obtained and
used for a study of lineaments in the epicentral region.
437
Mr. Ronald B. Robie -3- OCT 3 0 1975
Both vertical and low sun angle aerial photographs were
obtained in the epicentral area and will be used both for
geologic mapping of the epicentral region and for detection
of features that might be faults .
Geologic mapping is now progressing northward from the zone
of surface cracking toward project facilities . Discussions
have been held with Division of Mines and Geology to have
them do some of the geologic mapping in the epicentral area
at their cost. Discussions also have been held with PG&E,
Woodward-Clyde Associates and U.S. Corps of Engineers on
the problem of obtaining a better understanding of the
regional tectonic framework of the western Sierra Nevada.
Objectives of all these activities are:
1. Identify the causative fault and determine its relation
to project facilities.
2. Obtain better knowledge of geology in epicentral area
in order to decide if Oroville Lake was a contributing
factor to the earthquake.
3. Get a better understanding of the regional tectonics
to better evaluate potential for future seismic activity.
Cost: Aerial photos, imagery, etc. $ 7,000
Trenching and other exploration 15,000
Staff time 1.5 man years 6o,000
$ 82,000
2d. Further contact with Board members revealed that computation
of stresses in crustal models had been undertaken at Cal Tech.
and U. C. Berkeley. Only preliminary results were available.
The Board members indicated they had no further recommenda-
tions pending completion of these analyses. Upon their
completion your staff will review the results with the Board
to determine whether or not additional work is desirable.
Cost: None at this time
3a. Graphical presentations of various recorded seismic data were
developed. Noteworthy accelerograms are being digitized.
Some of this digitized data was ready by the time of the
Special Board meeting.
Cost of data preparation $ 3,000
438
Mr. Ronald B. Robie -4-
3b. A permanent seismic station near the epicenter of the
August 1st shoctc will be established. A site has been
selected and right of entry acquired.
Cost: Staff time, planning & design $ 4,000
Equipment, materials & construction 4,000
$ 8,000
Three DWR portable sensitive seismographic units are presently
installed and operating near Oroville, including one about
3 miles from the main shock: epicenter. Two portable visual
recorders are needed for portable units to aid in fast and
precise determination of epicenters for calibrating a par-
ticular area for accurate epicenter determination.
Equipment cost: $ 8,000
3c. Five SMA-1 strong-motion accelerographs have been ordered
to replace and augment Oroville Dam strong-motion instru-
mentation. The instruments will be installed one on each
abutment, two on the crest and one in the core block.
Six SMA-1 strong-motion instruments have been ordered to
provide for emergency situations, such as the Oroville
earthquake, to augment existing instrumentation on SWP
structures. Three of these will be installed temporarily
in a triangular array around the Oroville epi central area.
In addition to the equipment cost below, there will be some
additional cost associated with maintenance of the equipment.
Equipment cost: $21,000
3d. The Division of Operations and Maintenance's procedure for
responding to significant or unusual seismic activity
affecting SWP structures entails augmentation of existing
instrumentation where needed. A check list of possible
additional courses of action will be compiled for use in
future earthquakes including review of instrument maintenance
practices.
Cost for augmentation of instrumentation
at Oroville is covered under Item 3c.
Cost for additional instruments for
the remainder of the project $48,000
439
Mr. Ronald B. Robie -5- OCT 30 1975
3e. Processing of the dynamic data is covered under Item 3a.
Nondynamic data are being plotted on expanded scales for
clarity and increased functionality.
The properties of the materials in Oroville Dam that can
be derived from acceleration and stress data recorded
during the earthquakes will be evaluated. This work will
be accomplished in similar manner to that covered under la.
with funding by D&C, the work accomplished by Division of
Safety of Dams' personnel, and Dr. Seed utilized in a
consulting capacity.
Cost: Staff time, nondynamic data
processing $ 8,000
Staff time, stress analyses 40,000
Contract work. 10, 000
$58,000
3f. Improving seismic data collection at other SWP facilities
is now in progress. New insights gained as a result of
the Oroville earthquakes will be incorporated in a total
system reevaluation.
The costs involved with this item are included under
Item 3d. or are presently otherwise budgeted for.
3g. Department personnel will review Oroville instrumentation
program auid modify to strengthen elements where deficiencies
may exist. Of particular need is a real time base (WVTVB)
and a noninterruptable power supply. Replacement of the
four existing recorders for the dam dynamic instrumentation
is under review.
Estimated cost (including recorders) $25,000
3h. Surveys discussed under this item are included with Item 2a.
Special Consulting Board for the Oroville Earthquake
1. The preceding comments on the report of the Consulting Board
for Earthquake Analysis have generally outlined the program
and progress on the calibration explosion, geologic mapping,
and dynamic instrumentation supplementation.
Additional lake stage recorders in the upper arms are planned
for other operational purposes. It is believed that these
recorders will serve the Board's intended purposes; however,
a thorough evaluation will be made.
440
Mr. Ronald B. Robie
_6- OCT 3 0 1975
The Department will review its programs for both the
maintenance of the instrumentation and for the processes
for handling and evaluation of records. At the present,
responsibility for these activities is vested in the
Project Surveillance program with participation by both
the Division of Design and Construction and the Division
of Operations and Maintenance's Earthqualce Engineering
Section.
Estimated cost: Included under ongoing programs.
2. Your staff agrees with the Board's conclusion and thanks
them for their commendation.
3. See response to Item 2c of the Consulting Board for Earthquake
Analysis Report.
4. The design earthqualce motion suggested by the Board, modified
February 1971 Pacoima recording, will be used for analyzing
structures in the Oroville-Thermalito Complex. In addition,
safety of the structures will be evaluated for the other
suggested events: Magnitude 8.5 at 100 miles and Magnitude
7.25 at 35 miles.
Due consideration will be given to the criticalness of each
structure within the complex when evaluating the intensity
of loading to be applied.
Cost: (Included under other items)
5. As stated under Question 4, evaluation of the criticalness
of each structure will be made and appropriate loading
criteria applied in the resmalyses for seismic safety.
Oroville Dam and the spillway will, of course, be given
maximum treatment. Suggested analyses for Thermalito
Forebay and Afterbay Dams will be accomplished.
Analyses of Oroville Dam (previously listed)
Analyses of spillway & other
structures (previously listed)
Analyses of Thermalito Dams :
Staff time $30,000
Soils testing 40, OOP
$70,000
6. This subject is commented upon imder Item 2d of the report
of Consulting Board for Earthquake Analysis,
441
Mr. Ronald B. Robie -7- OCT 3 0 19/5
7a. It is our intent to utilize all data developed by others in
the evaluation of seismic safety of the Oroville-Thermalito
Complex. Similarly all data developed by the Department will
be shared with those cooperating in the studies, in preliminary
form as the studies develop, and in report form upon their
completion.
7b. Detailed procedures for analyses of Oroville Dam and the
necessary soils testing are being developed.
7c. The emergency plans for dams and the procedures for continuing
operations of plants, or for return to full operations in
event of shutdowns due to earthquakes, will be thoroughly
suialyzed relative to completeness or adequacy of assessments
of potential damages .
7d. Your staff agrees with the Board's conclusion. No other
comments are necessary.
Estimated cost: Included under ongoing programs or
under other items above.
The total estimated cost, as listed above, for implementation
of the Boards' recommendations is $520,000. For clarity the
costs are summarized in the table below.
Item
Earthquake Analysis Board
la. Reevaluate seismicity & design criteria
2a. Surveys
2b. Calibration explosion
2c. Mapping
2d. Crustal models
3a. Seismic record processing
3b. Seismic station
Portable sensitive seismograph units
3c. Strong motion accelerographs
3d. Augmentation of instrumentation:
Oroville
Remainder of project
3e. Evaluate properties of dam
3f. Improve data collection
3g. Review Oroville instrumentation program
3h . Surveys
442
Cost
Budgetin
($1,000)
Organizat
102
D&C
55
O&M
40
O&M
82
D&C
-
D&C
3
O&M
8
O&M
8
O&M
21
O&M
O&M
48
O&M
58
D&C
25
O&M
-
O&M
Mr. Ronald B. Robie
OCT 3 0 1975
Item
Special Board
Cost
($1,000)
Budgeting
Organizatioi
1. Implementation of Earthquake Board recommendations
2. Structure performance
3. Fault identification
4. Design earthquake
5. Seismic reanalyses 70
6. Crustal models
7. Other recommendations
D&C
D&C
Cost: O&M Budget
Cost: DSsC Budget
Total Cost
$208*
312
$520
With your approval the program described above, responding to the
recommendations of the Consulting Board for Earthquake Analysis
and the Special Board for the Oroville Earthquake, will be
implemented.
APPROVED:
/Director
K />/7r
Date
Attachments
♦Implementation of 04M related items will require a budget
augmentation of $187,000.
443
23 November 1976
Report of the Special Consulting Board
for the August 1, 1975 Oroville Earthquake to:
Mr. R. B. Robie, Director
Department of Water Resources
At a meeting on November 2Z and 23, 1976 with the Special Consulting
Board for the Oroville Earthquake, DWR staff members reviewed the work
being done by the Department on the seismic reevaluation of the Oroville
and Thermalito dams, structures and equipment, as supported by the
related geological, seismological and surveillance observations accumu-
lated by DWR and associated agencies. At the conclusion of the meeting
the Board was asked to respond to six questions. Our responses are
presented belo'w:
Question No. 1. A considerable amount of work has been done along the
western Sierra Nevada by various groups since the last Board meeting.
Much of this work has been directed at trying to evaluate future seismicity.
Has anything developed that would make the Board want to change the
recommended earthquake motion for reevaluation of Oroville structures
(report on September 12, 1975 meeting)?
Response. Since the last naeeting of the Board, substantial investigations
of past and potential future seismic activity along the western Sierra
Nevada have been made by the Department of Water Resources, by
Woodward Clyde Consultants, and by the U. S. Army Corps of Engineers.
We are not aware that these investigations have produced any information
to date which would cause the Board to change the earthquake motion it
recommended in its response to Question No. 4 in the report of
444
IZ September, 1975 for seismic re-evaluation of the Oroville-Thermalito
structures. However, a special supplementary motion, applicable only to
high frequency structures and facilities, is discussed in answer to Question
2 below.
Question 2. Does the Board have any comments or recommendations con-
cerning the results or methods used in the seismic re-analysis of the
critical structures completed to date?
Response. The Board considers the methods being used thus far in seismic
re -analysis of critical structures to be appropriate and, in general to
represent the current state of the art. It is obvious that care is being taken
to model the structures in a realistic manner and to consider the dynamic
aspects of the problems at hand. In most cases, final results have not yet
been obtained in the sense that calculated stresses and strains have not
been compared with allowable values. This aspect of the work should be
pursued with vigor.
The matter of allowable tension in concrete should be resolved to the
extent practicable at this time, with specific quotations from authoritative
reference material. The appropriate extent of dynamic water loading of
the 3D models needs to be resolved for the spillw^ay system.
The Board recommends that, for critical structures with high funda-
mental frequencies, the previously recommended time history of earthquake
motion be supplemented by a time history meeting the high frequency
(10 Hz or greater) requirements specified by the Nuclear Regulatory
Commission in its Regulatory Guide No. 1. 60, with the spectrum scaled
to 0. 4 g at zero period.
445
Care should be taken in analyses, and in evaluating the results of
analyses, not to compound safety factors by using only the most critical
results or conditions in a sequential fashion.
Question 3. Does the Board have any conclusions regarding the possible
relation between Lake Oroville and the Oroville Earthquake sequence?
If not, does the Board have any recommendations or comments concerning
gathering of additional data or making further analytical studies to enable
reaching a conclusion in the future?
Response. At its meeting on 1 1 August 1975, the Consulting Board for
Earthquake Analysis Indicated that conclusions regarding any causal
relation between Lake Oroville and the 1975 Oroville earthquake sequence
would be difficult to reach. It was suggested that certain observations be
made that might throw light on the matter. Even with more definitive
seismological and geological information related to the sequence now
available, however, it still appears that it is not possible to draw any
firm inference on whether the earthquakes w^ere, or were not, triggered
by the reservoir.
It should be noted that the problem of association between large
reservoirs and nearby earthquakes is now receiving considerable attention
w^orldv/ide, and much research on the problem is now under-way in the
United States and abroad. We recommend that the DWR take steps to
keep informed of the results of this research, with a view to possible
application to the Oroville situation and other DWR facilities.
Question 4. Does the Board have any recommendations or comments
concerning the draft copy of Bulletin 203 before it is published?
446
Response. Bulletin 203 will be useful as a documentation of the performance
of the dam and related facilities during the August 1, 1975 earthquake and
aftershock sequence, and as a vehicle for distributing the wealth of seis-
mological and geological data gathered before and after the earthquake. In
this regard, the Board believes Bulletin 203 should be limited to include
only data describing the seismic events, related geological studies, and
performance of the structures. Although there are numerous minor
editorial comments which could be made, at this time the Board offers
only the following specific recommendations:
(a) A more appropriate title would be "Performance of the Oroville
Dam and Related Facilities during the August 1, 1975 Earthquake. "
(b) The purpose should be clearly defined in the beginning of the
report.
(c) The final draft deserves further editing to achieve uniform presen-
tation of the findings and conclusions.
(d) In reporting the factual observations and events, care should be
taken to avoid the inference that the Department has made a
definite conclusion regarding the relationship or lack of relationship
of the reservoir to the earthquakes.
(e) It is requested that the listing of the Board members on an
introductory page of Bulletin 203 be deleted, inasmuch as the
Board has not participated in preparing the report. It Is similarly
recommended that the reports of the Board included in Appendix D
be deleted.
(f) The re-evaluation earthquake studies, recommended previously
by the Board, apparently will not be completed before mid-1977.
Hence, any conclusions and recommendations relating to such
447
studies would be premature at this time. It therefore would appear
appropriate to issue a separate bulletin or report on this phase
of the work in late 1977, as a follow-up to Bulletin 203.
K the foregoing concept is adopted, it would seem desirable
that Bulletin 203 include a specific list of all damages to the
Oroville complex resulting from the Oroville Earthquake, together
with a notation of the type and cost of repair work completed.
Question 5. Does the Board have any recommendations for future geologic
work?
Response. The Board emphasizes the value of determining and attempting
to understand the growth of surface faulting following the Oroville Earth-
quake, and it urges that this work continue to be pursued vigorously. On a
broader scale, it is important, to the long-term safety of the Oroville
Project, that the geologic environment associated with the Oroville earth-
quake be understood as well as is realistically possible. Two important
questions are (1) what is the relationship of the surface faulting associated
with the 1975 earthquake to the mapped surface geology, and (2) what can be
said about possible future northw^ard extensions of the 1975 fault break?
Answers to these questions will undoubtedly require additional trenching
and additional detailed geologic mapping. Including areas north of the lake.
Continuing efforts should be miade to relate local geology to geodetically
observed deformation patterns. To do this effectively, the area must be
re-surveyed for elevation changes at regular intervals, preferably semi-
annually, for the next several years.
448
Question 6. Does the Board have any other comments or recommendations
to make at this time?
Response. The Board offers the foUowing comments and recommendations:
(a) The Board would like to draw DWR's attention to the small but
finite, likelihood of a future recurrence of an earthquake sequence
similar to that of 1975 near to Oroville Dam and its associated
facilities. Somewhat analogous seismological and geological con-
ditions in other parts of the world make it not implausible that
a possible repetition of the sequence may occur northward from the
1975 events. Indications, if any, of the above development should
be sought in future seismological, geological and geodetic
monitoring,
(b) The Board believes that there is urgency to complete the re-analyses
of all of the dam elements in the Oroville- The rmalito complex at an
early date, in order to determine whether any reinforcement may
be required to assure ability of those structures to resist the effects
of a 6. 5 magnitude local earthquake,
(c) The surveillance attention being given to the project is commendable.
The surveillance provides early detection of damage but time in
which to mobilize effectively for major emergency repairs required
by seismic damage to embankments would probably not be available.
Therefore, inherent structural integrity must be the alternative.
In particular, the most critical portions appear, at this time, to be
some locations along the Thermalito Forebay and Afterbay Dams.
Accordingly, it is recommended that locations of critical sections
of these dams be determined on the basis of the existance of
449
low-density soils, particularly loose sands, in the foundations.
Field sub- surface explorations, followed by analyses of these
sections under the effects of the "re -evaluation earthquake, "
should be carried out on an urgent basis and, where potential
instability may be indicated, corrective designs should be
developed and the construction accomplished as soon as possible.
450
J
Respectfully Submitted,
C. R. Allen
John .W. Blume
Bruce A. Bolt
ffh-i£0u^yX\ y
Wallace L. Chadwick
eorg'e W. Housner
T. M. Leps T
Alan L. O'Neill
'hi lip dj Rut:
X^JuUjj-i^X.
b
Philip (\J Rut ledge
H. Bolton Seed
451
Memorandum
The Resources Agel
To : Ronald B. Robie
Dote : MAR 4 1977
Robert W. James
From Department of Water Resources
File No.:
Subject: Oroville Earthquat
of August 1975, Proposed
Department Activities in
Response to the Special
Consulting Board Meeting
November 22 and 23, I976
Presented below is a description of our program to implement the
recommendations made by the Special Board for the Oroville Earthquake]
of August 1975, in their report transmitted to us by letter dated '
December I5, 1976, for the meeting held November 22 and 23, I976.
The recommendations generally concern completing analyses and work,
initiated as a result of their recommendations in reports dated
August 8, 1975 and September 12, 1975^ and outlined in my memorandum
to you dated October 30, 1975. Our response to each item in the
Board's latest report is listed below by number as they appear in
their report. A copy of their report is attached for reference:
1. No changes are required in the earthquake motions that are
being used in our reevaluation of Oroville critical Structures
except for high frequency structures and facilities. Our
action concerning these structures is covered under Question 2.
2. The staff agrees with the Board's comments that final results
of the dynamic analysis be pursued with vigor and the final
results be compared with allowable values. It is intended to
proceed as rapidly as possible with the analysis. A funding
augmentation of $300, 000 has been approved for the remainder
of this fiscal year and it is now estimated that we will need
$166,000 for 1977-78 fiscal year. The additional funds were
needed because the scope of the investigation was expanded.
The problem of allowable tension in concrete for dynamic or
transient loads has been given considerable study in recent
years as recent dynamic analyses of concrete dams have
indicated larger tensile stresses than earlier design
procedures. It is intended that we will determine what
allowable tensile stresses can be used by a search of
authoritative reference material to support our contention
that dynamic tensile stresses indicated by the analysis
are satisfactory. We will be investigating the extent
of the dynamic water loading of the 3D models for the spillway
system.
452
Ronald B. Robie
Page 2
Both the diversion dam and the spillway have fairly high
fundamental frequencies, therefore we will investigate the
structures for the higher frequency ground motions as
recommended by the Board.
We have attempted to evaluate the performance of the
structures realistically and not compound safety factors.
We have initially evaluated the structures conservatively
and refined the analysis if the performaxice appeared to be
questionable. We will continue to examine our results with
this in mind.
3. We plan to Iceep informed of the results of research in the
association between large reservoirs and nearby earthquakes
by studying written material as it is published and by
observing performance of structures in California. Of
particular interest will be New Melones Dam on its initial
filling. At the present time no additional funds are needed.
4. The report will be rewritten to include only data describing
the seismic events, related geological studies, and performance
of the structures. Conclusions from these studies will be in
the final report after all studies are complete.
(a) The title has been changed as suggested to "Performance
of the Oroville Dam and Related Facilities during the
August 1, 1975 Earthquake."
(b) A statement on the purpose has been added to the foreword.
(c) The Report Administration Section in the Division of
Planning has edited the bulletin to achieve uniform
presentation of the findings and conclusions.
(d) The section discussing the relationship of the reservoir
to the earthquake has been rewritten to avoid the inference,
The conclusion on this subject will be in the final report.
(e) The listing of the Board members has been deleted from the
introductory page. The Board members are still listed in
the text where it is discussing that a Special Board had
been established. The Board's reports have been deleted
from Bulletin 203.
(f) The final report will be a "follow-up bulletin" and
include the conclusions from the many studies now in
progress, and the Board's reports.
A section is being prepared to list the damages to the Oroville
Project Facilities including the type and cost of repair work.
453
Ronald B. Robie
Page 3
5. We concur with the Board's recommendation that an understanding
of the growth of surface faulting should be pursued vigorously
and that it is important to the long-term safety of the Oroville
project to understand the geologic environment associated with
the Oroville earthqualce. The Project Geology Section has
developed the following program for geologic investigation to
comply with the recommendations of the Special Consulting Board
for the Oroville earthquake:
(a) Determine the extent of the fault thought to be responsible
for the Oroville earthquake. It is particularly important
to determine where the northern extension of the fault is
in relation to the Oroville facilities.
(b) Verify the nature, age of last movement, euid extent of the
two faults previously mapped by others just west of Orovill
Dam.
(c) Do geologic mapping in the Palermo and Bangor quadrangles.
Also do geologic mapping north of Lake Oroville. Do
geologic mapping of Tertiary formations in the vicinity
of the O&M Headquarters .
(d) Investigate the Palermo Crack Zone-Prairie Creek lineament 1
to see if it is a fault system that could pose a hazard !
to project facilities. Continue investigation "of the
Paynes Peak, Swain Ravine, and Prairie Creek lineaments,
and other suspicious lineaments, both north and south of
Lake Oroville. This will involve extensive field studies
including both geologic mapping and trenching.
(e) Continue study of ground water levels in the epicentral
area to determine interrelationship of local ground water
systems with Lake Oroville.
Target date for completion of the above program is July, 1978. In
order to meet that target date, we anticipate that four DWR geologits
will work full time on the program. Additional temporary assistance
may be required to do some geologic mapping. We anticipate the
additional assistance required for geologic mapping possibly might
be done by graduate students during the summer of 1977 and possibly
the summer of 1978, but this kind of arrangement has not been exploit
yet with the universities .
Estimated cost of the geological program is $l43,000 for 1976-77 anc
$334,000 for 1977-78 fiscal years. It will be necessary to hire twc
additional Junior Engineering Geologists to carry out the program.
454
Ronald B. Robie
Page 4
The Division of Operations and Maintenance plans to resurvey
this area again during the summer of 1977 with its precise survey-
crews plus a maps and survey crew if one is available to determine
deformation patterns. Estimated cost for the resurvey is $8o,000.
6. (a) We concur that we should be prepared for additional
seismic events in this area. Monitoring of seismic
activity in the Oroville area will continue under the
Division of Operations and Maintenance Earthquake
Engineering Program. Our current plans for geological
and geodetic monitoring are covered under our response
to Question 5.
(b) We plan to have the re-analyses of all the dam elements
in the Oroville-Thermalito complex completed next fiscal
year, 1977-78.
(c) We concur that the structural integrity of Thermalito
Forebay ajid Afterbay Dams under severe earthqualce loading
is uncertain. We are in the process of evaluating the
stability under the recommended loading and expect to
have these completed next fiscal year 1977-78.
Attachment
cc: H. H. Eastin
G. W. Dulcleth
J. W. Marlette
455
APPENDIX B
ACCELERATION TIME HISTORIES AND RESPONSE
SPECTRA FOR THE AUGUST 1, 1975 AND
SEPTEMBER 27, 1975 RECORDED MOTIONS
ON DAM CREST AND BEDROCK, IN UPSTREAM-DOWNSTREAM DIRECTION
(FIGS. B-1 THROUGH B-8)
457
458
fldCEliERflTIbN iRe^P 5PEt-
:LLE ^DRM JCREST N4BE 8-1-15 USGS !
:ng + zL B^i.ioxUozi I : \
Figure B-2. Computed Acceleration Response Spectra for USGS August 1, 1975
Crest Motion
459
Figure B-3. USGS August 1, 1975 Recorded Rock Motion
460
1 V- --i-^sf 1k^^^-(^i^^^^1=t;tTx4fi^&TVd^^--0=ip
H|.J?!f!^!:.r Pv^M^HtiiN il!li4_li||:::,:3
im 1 1 I 1 ! .1 1 1 ___ ,
1 1 1 1 1 1 1 M i M 1 1 i LP
1 1 ; ! 1 1 III 1 III 1 " J^" " vi^'i
■ 1 M ^ ' ' 1 ' 1 ' ' 1
1 A. _L J . - .. .... L_i_ _^ .. 4 . . _j_ .i
1 ^- j 1 1 -^ -Tji rr r -^i [—
'^ . . \ ^ 1 " ' T T "" " " ' T
- - - - - - - - — - - ^- .-- J-. . - - . ---- X- - ^
t.3
T^ - ■- - -- -'- '- -" " _p
i:S-____„_:i:_:::_:___:::_::_:::_:„___::::_::_ ___::::::::.:::::
Ej:- - - -[T - T --- -^- - - ---T -- --
^: :.„:.;;:: .;- :::i-:,:: ::/ _.:::::-.::: ::_::::ir_:__:i: '^-■'----=----"^-T--- ------
c ^ -. - - - - - -. - .- . --. - - .- - - -
^i^ : :::_::::_;: ^ :_ _ _/ __ _ ._" ^ ' " ._
I^^pc
^'"".. .:: : i'^: i _/ : .... ^ ._ .. " " _ "" " . " ._
i -T
^; T ■ - -.
,:_^-.__|_L._„::_::::::=::::::::_:::::::::::=:::=::::::=:::::_.__::
::::":? V ::::::::::=:i:i:Ji:::i:::i:=::::r:::iii::iii::i=:::::::
., -~~ -W'^ \, * -.. -.-" "" ^ . : "
'"''''T'\\\\""'""'""'" """""""""""""""'""'
,::::: J____\H:^-^____----_:_:_:::-:::::::_.-:::--_-___-_-_-_:_-._:::
.._::::::.::- :::^sN^V^/^-'~-:^.- ^ \ '-""- =-' - ----- -= =
- --^ - ---Sr- ^ ''--::-s==- ..>^5;--- — - - - - -
- ^ -- - - -- — "2 """^^ = = =■--= = >,_ .^^__^ _-__., -
1 frHtt-Hi riTl- pemOTl imoNoii [ITlHi-[frihF[TH'HB;hHfH:n
Figure B-k. Computed Acceleration Response Spectra for USGS August I, 1975
Pock Motion
461
462
Figure B-6. Computed Acceleration Response Spectra for DWR September 27, 1975
Crest Motion
463
464
Figure B-8. Computed Acceleration Response Spectra for DWR September 27, 1975
Base Motion
465
APPENDIX C
STATIC STRESSES FROM STATIC FINITE ELEMENT ANALYSIS
(FIGS. C-1 THROUGH C-8)
467
s 5 J : c s = 2
^-
B?«S55 = EltSM
IS S» ; S 5 E 15 2
ii es z e 9 i § 91
Vi
^>-
469
0;ROVILLE DAM -MAXIMUM SECTION
470
Figure C-3. Major Principal Stresses, O] (tsf)
471
4
OROVILLE DAM - MAXIMUM SECTION
472
Figure C-4. Minor Principal Stresses, o^ (tsf)
473
oroviiIle dam -maximum SECTIOK
I
I
F^r SI,.*,. £ .-^T, ^^'B
I
474
r<...^.'v.f
/».= ■• »'ra
Sfe*.
'■» h"^
L -t-^^J.
' / =.3 V
!.«
'•+-
.0 1 s., '
S.5
V-\
s/ .. y
6-0
^1
/^.3 Z
'.s
s.o /;
^.^
s 1 A,
«9
3., V^
>|.,
J^/n.e
U..
1 9.0
'
.3
«.0 -^
- / -
■.J.7
1
.5
4.4
V]^
' 31.3
U.5
13.^
>
0.5
i ' '
I..2 \
/1 ,S.S
.
2.5
1 5.7 /
^■^5^^^
,2.3
19.6
1 ,
5.2
i" w
p.3
2.. 4
1 '
7.0
14..
1 10.3
IM.S
^--^
21..
22..
'
..»
12 6
' " /it>-
?l.l
S.7
3.4
1^
.2
18.4
.5,0
.1.2
1"
I 3.3 "■--
.^
26.8
2S.;
3.3
20.6
1 ,7.2
13.5
9.B
j SJ /fs^-,.
V.B
26.9
27.4
2
5.5
22.7
.6.0
12-1
8,4
" ^
- iX£
23^
XLa
U,
3t.^
21J _
.a^
lk.7
U).S
1 8.6
'•ij^^--^
33.3
S.9
9.3
27.0
20.5
j .6 3
.29
! - /la-..
3,.B
3E.S
33.9
3
-3
29.3
26.2
22. a
.3
2
1 "'
79
3,3 V
*+-
1 37,5
37.4
36.2
4..
31,5
2B5
25.,
6
1 14.0
1.0 .^^
1 39.5
1 38.4
6.3
1 33.7
1 30.7
27.4
1 23
8
1 20.1
j .6.3
i B,6
1 "'
;^.
42.3
1 40.7
B.9
33.,
,
23.B
26
3
22.6
1 iB.a
15.0
■ 10.3
47 \,
43.6
43.,
0.6
1 38.2
35.2
28
4
2V.B
i 21 ,
.7,4
13.3
1 3,5
; - /^\
. 4£.4
4^.9
1 "
3.0
M.4
!t7.,
1^.2
■ 30
7
1 "■'
, 23.5
.9,7
.6.1
I ...7
1 ''
r ^-^
1 SO. '
L-^ L
1 49.0
J *■'
1 "
42.5
1 ==■'
L^Jll^
*— 1—
°
1
1 26. 9
L^ 1
22.1
4^^^^
1^4^^
!- \^^
Figure C-5. Vertical Normal Stresses, a (tsf)
475
OROVILLE DAM - MAXIMUM SECTION
476
Figure C-6. Horizontal Normal Stresses, a^ (tsf)
477
I
OROVILLE DAM - MAXIMUM SECTION
I
478
^n
n2«J''V^:
■-..
fr~-
^
v^
^>>
/■' jl \
^\
^>^
f't/'A '-'i
^ J f
I.1{
"V
1-7'
1 • t-J --s
i^ ■' y
e.>
.;!>
« ^A.t
"■-«i ^-
^,-ir-"-.
'\ \
• ^.^t^"''
SX;
,J
1
">
/,,J\*
S-^
"1
H
^:^,
'-4 --
>.7
5*
,.3^X
^
■^
1 '■'
^3,
1.3
,..'
" 7.^:?-^
/ '■'
"1^:
1.1,
A\
i.i
3J
,., V
A s-"
«.<
••'
■■<
. ^A
1.3
3.1
^
t^
(«'
.^'
*
s-*
1.T
3*!
34
t^<
•«
1.1
»
9^
C-3:
^A
3.e
J^
e.7:
»■«>
A
ejii
'•1
(J>
1.0
>.i >;
>^
^
6J
e.«
<
T*
.^1
IS
1.7,
'I \
-1
"1
■*
•■5
4.3,
»J
«!
>*
ti^-'-V.^
^^.
(4)i
A \
1
t-r,
, '"'j
.Jl
(X.
■"l
H J
--t -
- 11.^ -
-M- -'. ■
D.-f
■ '4 ■
■ ■ r.* -
' --4 ■
" •«
"^-r-TT
I*
-3=4-^
..r^
u.fl
■'•^
XX.i 1
1.1
10.1
9«
:i
1«l
•■»l
'■'"^\
le.t
ir.) «
C.ll
1..J
Ul.«
f.fi
• Jl
7.t!
1-0
3J1
tX'
T>--^
13.1
13.1
»•• I
3.J
1C.1
u-l
lO.J
3.e
1.1
tJ
».7
K
3.1
..3\
13.1
IH.l
«.3 I
13.(
If. I
11. 1
10.»
8.9
.7
...
..3
1/1
" /rx.
IB..
It.t
S.l 1
H.»
13.1
...J
11.1
10.1
3.7
■ .«
7J.
..c
1J1
i^
">-
"•1
■••'
lS.d 1
'•1
W.*
13.«
"1
11.11
10..
• .<
..3
7J>
...
V3
- 1 -^
Figure C-7. Maximum Shear Stresses, T^ax (*^sf)
479
OROVILLE DAM -MAXIMUM SECTION
480
i.,fc,oU^».
,
■'-^
( \
* -Oil \
--
^
I.
/ ~^'^ V
-l.» H
i^
i.
1 ^» \
-1.7
^>
s
/ -1 1> ,/
-1.7'
-s.sT--^
^
/
-S-2
''' (
/-a-H
.e /-o..
-s.s
-'V-
^
fi.
=r^-Q.i -
- -iJ.
-3.0, -
-iJi —
-;.g^
^
/ 0.3
-2.»
-J.9.
-3.3
-J.J
r
-;:^,
3
/ ^\^
-1.9
-J-9:
-3,5
-9 51
/
-2.0
-3.0
-3.6
-3.6
"■• '
' -2.1 ^.^
/
-0.7
-1-3
-3.S
-3.5'
-t.O
-2.3 ^
Is.^
\
^H
-S.I
-3.0:
-3.9!
■^.1:
-<.2,
-9.4
~2!2>-^
-0.9,
-E.31
''1
-..0|
-..31
-■4.«l
-9..,
^•1 /
^^1
--
^T.r
- --!rB|- --
" --^fTt —-
— T.if
-"Jl.tf —
Jl.T
-TI.J'
n.T^'^
.J
-2.3!
-2.9
^.0,
-«.2I
-<.»
-,.7'
^.5
■«.o,
-3.1
-2.
>.^
-2.2l
-3.5!
-«.4|
-H.7'
-,.9!
J..7:
-H.4l
-H.l
-2.5, \
•^
-« B
-3.^
-• U|
-•1^
dl-S
ia
^.JUL ,.
J1.7|
. .^i-lf-. ..
A \
-2-
~>.^^^
^.s!
-,.5
-».3|
5.0!
-E..'
-E.2
-E.l
-«.*
-3.» 1
-^^^-v.
-».9
-».8'
E.r
-E,3l
-E.J
-E.3
-E.l
-..9,
-«
31
-3
9"
^^N>.
-t.2:
-E.O
-E.3I
E.3i
-E.S
-S.61
-B.5
-E..
-s-i
-H
61
-«
2
^Tr^-^
-6.3
-E.sl
E.6,
-5.7
-s.e'
-E.e
-5.7
-E.l
-E
0
-.
5
-3.7,
-2.7
^
-ta,
-E.5
"'•'1
E.e.
-e.oi
-6.0
-6.1
-E.S
-E.7
-5
9
-«
6
-..1
-3.»
-2.2 ^\^
-6,,'
-E.9'
-5.7'
6..
-6,2
-6.31
-6.3
1 -6.2
-6.0
-5
6
2
-<*.5
-3.8
-- /f^N
" -TTf
—^5^
'~^S?T-~-
"
-E.7
-c.a --
" ---E.? ■
-6,E
' -6.? '
-6.3
-s
0
-5
6-
-5.0
-u.f
-3.T
-""^^
-S.*
-6.41
-E.9|
-6.S| 1
"'1
-6.9:
-6.9.
-6.0
-6.7
1 ■*
■.
9
-5..
-^.7
-3.6
-2.7 1 -,.>-^
'
Figure C-8. Horizontal Shear Stresses, x^^y (tsf)
481
APPENDIX D
TIME HISTORIES AND RESPONSE SPECTRA
FOR REANALYSIS EARTHQUAKE
(FIGS. D-1 THROUGH D-6)
483
Figure D-1 Accelerogram
for Reanalysis Earthquake
Figure D-2. Computed Velocity Time Histor
for Reanalysis Earthquake
Figure D-3. Computed Displacement Time
History for Reanalysis Earthquake
484
Figure D-^. Computed Acceleration Response Spectra for Reanalysis Earthquake
485
i
Figure D-5. Computed Velocity Response Spectra for Reanalysis Earthquake
486
Figure D-6. Computed Displacement Response Spectra for Reanalysis Earthquake
487
APPENDIX E
RESULTS OF DYNAMIC FINITE ELEMENT ANALYSES
FOR RE ANALYSIS EARTHQUAKE
MAXIMUM SECTION ~ SHELL K- , = 350, 200, 130
2 max
ELEMENT STRESSES AND STRAINS CFIGS. E-1 THROUGH E-18)
SHEAR STRESS TIME HISTORIES (FIGS. E-19 THROUGH E-39)
SECTION 2 ~ SHELL K- = 130 - LUSH AND QUAD-4
2 max
ELEMENT SHEAR STRESSES AND STRAINS (FIGS. E-40
THROUGH E-45)
ACCELERATION TIME HISTORIES (FIG. E-46)
SECTION 3 — SHELL K„ = 130 - LUSH AND QUAD-4
2 max
ELEMENT SHEAR STRESSES AND STRAINS (FIGS. E-4 7
THROUGH E-52)
ACCELERATION TIME HISTORIES (FIG. E-5 3)
MODEL EMBANKMENT — SHELL K„ =130
2 max
EFFECT OF POISSON'S RATIO ON STRESSES (FIGS. E-54
THROUGH E-55)
489
m
i^.i'llii
1
/jjR9BaBB«
i 5 6 r « 8 K J B = 11
/
/£CSSBSI9i:E9 8 9CU:
/
(;8!»CSP=tl!i!J66«S = BlJBC9 = «
?!^tr!i|^! = ; ! 5 2 ; ! 5 ; ; ; !i ! ^ ;
l|g|4|ii|
^..Bl-U*-^^S^^«''^-S^-
V;5 3;S:;;;|lf 5»;|S'
^''°52'i«SIS"'°''
1.5|hl^5^^ = J.
^|;;5:«;-!:55::5
^sii'5!??^5J
i ?;5s ; 5;3;;
*■ ^61. a «« am
ill ^;i;;!.
J
4-> H-
C 1/1
1- C
o o
■JL —
4-)
E O
3 0)
E 00
">< E
3: E
490
491
i£?25S^?
A
{jfSSS'S:
• RSS8JISS
/
m^sltdqi^ltlSI
/
A J « « c
SIRCK1B~C
ii":::
eisafacas
i;!--?-:
»PHI«C6B59
ZuiicnBPSiiis
P«i«t«5(l*
;f<'"'°"""
IS ; a a 19 s e e Si
aie9sn888£
s^aKEtiiai
p?pS:|JJJ5==5;=
= :«;555B
:::iii^^;%^^
%V-llnl)t]
\:8^:'5^?l
?5«;^I-|
^:!:i:;^
fJintiteRBPai
^M^?^
; = <;4B28CJ
SE!-«3B;I!i
1 1:
!^^"!";fe^^
s ^
a a ^ K » 9 e 119,
1
<=> ^ rt (^51
-^ " "^ .
> Z X J tu
*Jq jj 1 » ? a =
2 '
V-
c
</)
f>
4->
N
~— '
u
r
O
0
I
•~
4J
F
0
3
0)
E
to
X
F
m
3
2:
b
492
:B8f:gC29B«« (/)
I « i I = a i 0 e « I
,3tB;e«i>. S8:
Lucssiaie^i
iS -Sijltoiiti
\:
; s S ^ t « flf f
i^tSt»i»Sf*il
I S'6 as ,
c
in
o
i->
N
^-^
l_
c
o
o
I
4_l
F
o
3
(U
E
to
X
F
nj
3
X
E
'< s 3 i: e 9 e 4
I.
4-1
(TJ
c
4)
a)
r.
o
<.n
\-
<u
tr
Q.
-1
^~^
f-
•—
r.
X
o
(D
—
• to
oo
I E
LLl 3
E
(U —
I- X
en 2:
493
(jsdl SS3a±S aV3HS
CD
to
ro
o Q
- O
o
UJ
UJ
en
S
a> LU
UJ
S
_l
usd) sssais av3HS
494
v\
A
^«?M
J??^5;!
i^fe'"'!
>^?5^s4:S;!;J
i!55i55||^S:»«^
£iuu^iAv.n'Ai*^
i^^^"^^l^^3''i''"l
|S§|f '^l----i
'-?5|^5!;|"s;'%:Qi
^555'5^i5!o=?M^^:^f3
^S;5535:!5'|^^J|F:J
\°-"'^"lJffll
^?55???|j!.5r.5^^
\ ^i,^,^.
1 « = S -1
S 5 s g 1
E *->
3 O
E 0)
•— (/)
X
(D E
z: 3
E
/5
i:::r:"
/.« = ..« = . J
/', J«p;s»sjjiisas
^=JbiJ9=osb;=s»e
/(8 8i«(!8!;P«8SH«« = 8»
4i '■"■'•■'''"■"'"""■" ij
^ i:-! = ! = JS555 = !;;:; = ';jJ
I /alll ll^llllll-il^llllimi
^i|i;sft*^l' ?j? = = ; f ! 5 « ; ; s ^ ? ? « !
/\^ig|^
^J«^«^^?;^^"^^;«:^;E:!'
- ~~~~^„— _^^_;^__J
^!!=;5?;;?!^|^nj=^
^;i!5!?!|^;!5:?^J:|
^SSliSSIiSSssts^;
S ^JJJlS'i??!
" 3 <^? » 5 « « i i:
;|£o - \!b^5.
1 I S i " "^
F
j-i
3
o
fc
(U
. —
(/I
X
m
H
z
3
E
X
■ —
(D
495
u
J
I'.r-t
i;s3 = |
/p 5 « B = 8 P » :
^;;s;sn|
i=ssn;!5 = |
/ ^ J C I J J 0 J B J S C L
ijS!!!:3»J5!S5 = ;lf?J
/
^;5355:;5555;?5555|
i5'5i = 555 = S;il?!;^5;|
jlBJS = « = S«SP« = S«aj»50»8 = S
y;if:^2;;-'E;;-= ==5*'^
fe^h>p^n«:^^;''"^"'l
^"-ssHi^^^.^n^:^^
^| = ;;j??K;?^'s^|:^'
^j;5;55^4jJH;Ji^iS
1^!!*5;>5; 5; SicJKgffi
^:I!?''"'5!''j« ssU^?
^HSBC^bS'SHUBBSJEJ
Isji^s^sM^II
hh'^iir.v.t^
I iB i
i ^ ^'--2Jj;5^
lis ° \:j_
°SS ' 1-6...=.
O t/1
N -M
E
'
r ,
- ■' "
^
! S
1
1
f
! = n
1
«
5
^
lii^
• jssi
<i
t:
s
<-
1
IS
i
= 1 7~
»-
f ^
Si 5 1
i ^
;ss«
' '^°
SSsi
p^
2 »!••
25 = 2
ro
4->
(U
c
^
(U
to
o
I-
F
(U
3
a.
E
"-'
X
c
OJ
o
ro lO
T E
LLl 3
E
jj ._
»- X
3 ID
496
1 1
A 1
|\
/ "'
L i
/ ,
/S -1
/f
A
'1 -1
|::>>;r--T:::;4
^-; — \/\, \,~-~._.^
\ \-"\ H ^
v:::::::::=:|=::
\ r--
\ /
\7r"'\
\ 7
V
\...J..
\
V--
V-
\
497
g!§:32?l»!!!5!i5i~
taseiti;:
^m S s 6 I I ;
;aS5i9<sc(
498
K'i
L
i\
A^aigsiiesi!:
/
/tl-»81!a!:li;«8«
t'jvtvjji
/..8... . = . = .,?
i^ ' ■ "■'
kv-AlMlMlM^A
/
/>'. >:;:£8:«f28Bli8Ba
i.-,-. -,,,,. ,,»^,.-
Z S « • « 8 8 « S » C I J 5 t 9 0 a 8
i------'----M
r; /iE8|ec60j(;tS«BBSIK9!)t8f9l8^
S , - -^ ; -^ ^ "■ ^ ^ -■ "^ -^ - •< "^ -< •< - -
1 /
l^s:rS = ««! = »B8Ssi:I!0ICB8i»B
'E is*--! s * 5 ' 5 5 « = ;;;;;-.; J 5 ;.; J J
^M;;K^J^ = !j*'i:;:5;:;;^
• %:i ?i?;'5!0;!^j*^
\vx^mm^
f-'-sisjiifKiiiN
^!;;!!;:!l;5i'{' «;;•;.;
\S « 8 e e 8 ; 1^ (1 E 8 » S 8 sc
%S^?5:5!5!:55:
i 5 • 2 a »; =• f E « 1 S 8 R R
,^ _
< D V 5 - J ;r K 5 SB
Sin = »-~~~----
1 S * ■■ ~ ?
^ 3 i ; .. 1??!
° s i : 51 V-
<
ID
C 4-
O i/>
N ■U
E -M
E 0)
•— (/>
ro
/
/« ! i !- 1 !■
,g II 1 M 1 1 1
SSii i 8 Bi III
/N° = = o o - •= ° - °
jig 8 S 1 ! 8 § 8 i 8 8 §
^o oooooooooo
A 5 11 II 8 1 8 1 § 1 S §
/[8E8!B9 = 8S9«aBSB§8E
,8 i 5 3 5 5 5 : ; 5 § S 8 5 8 5 i ? §
^|«!S?S£?;5SE = 88EE888B
-<''°°°°°°°°°°°°°°°°°°°
L 4I8SM5!S? 5555? - 5 = ??- ; s » 588
tepf|5ii!^!!^!! = ! = !!i$
\;-^i! 1 J ! s H i J T^i^i; "■ "■ "■ ^ cl
li!i!;!|j;5a.i|t!j{i!l
S\m\\\^\^>Ji^^Xi'f\
\A\\\\\l\l\iM,Wi
lBy8IB||¥55SS?=5
a£!8'|!;:!§?!iSi£
W?SB. = .,,«?,5
S ;||5i85S=S
^ 3 5?5?5?5-.
si 2 s %mii
s 2 ^ ; ,. • ' ^. "
" ^ ^ '~ iL° "1"
> 1 s =: " °k;
499
1 !
1
1
1 1 1
1 j 1 1 1
j .......... , 1 J
1 1 1 '
: 1
1
1 '
i 1
j
'
1
'
^ i
1
1
1
, 1
!
1
1
1
^ 1
1
1
1
, . 1
1 j 1,
^ ! !
ir-^
]
1
! I
"^ 1 I
^
1' ■
; 1 i
~^
1 1 ,
1 i
1
-h ■■ " 1
1 1 1
1
1 1
! 1
1
i 1 '
]
i ' ' 1 ' 1
! I
, 1 M ' 1 1
!
* 1 '
1 1 : , 1 1 { u i ; ' 1
I 1 '
DAM - MAXIMUM SECTION PROGRAM := QUAD 4
WAX - 130 LOWER CORE MODULUS
1 1
i '
1 M i
M 1 1 L 1 '
1 J
1 1 1 I
,
M
I'll
1 ]
' 1
1 '
1 , 1 1
1
I i 1 '
IlJ I !
' 1
' '
' 1
O : 1
,
I ■ ' '
j ' III'
1 !
"^7^
'
.11
1 ' ■ ' ■ ' ! M
, , ! ■
-t ' .
1 1 1
1 ■ .
1 1 1 1
, M
iq
I M 1
' ' ' II 1
I'M
'Ml
II 1 ;
'Ill
1 M '
1 1
! : , ! Ml Ml 1
1 . . [
' , i
■ 1 ' :
1
1
' 1 M M
' ' '
1 ' , 1
' I
K
' ' M 1 < M
1 ' ' ' 1
1
1 : j 1
5^
I'll
M K II 1 Ml M
1 M 1
■ 1 1 fl 1 1 1 J
^— ' Ml
,A '
n~
' '
■ 1 ' ■ ' 1 1
' M .
13 '
1 :
'' ■
; ! ■ i 1 1 1 M !
' ' ' 1
1
ill I'M Ml M
i ' 1 '
' ■
' 1
re U-J
M '
1 1
■ 1 1 1 1 1 1
!
j 1
O) 1
1 ' 1
'
1 1 ' 1
1 M ' MM M ' ' M 1
1 1 1 M ' ! ' :
; ■
1 j
0 '■
■ t ■
1 '
'
II 'Mil
1 ■ 1 1 1 1 ;
! 1 i '
, 1
-i i
: ! ;
i i '
M ' ' 1
' '
1 1 1 1
1 M 1
y ' '
,
!
1 Mm
Ml ' ' 1 ' V i !
M 1 ' III
_j
z —
■ ' ' i
1 1
■^
■ ■ ,
^' : ; ' M 1 ) M [ ;
1 1 ' ' 1 '
\ ; '
; I
■ , ■ '
1 1 i 1 < '
'
J -^
1
J i
M j i 1 Mr M M 1
. 1
■ j
1 1 ; 1 :
: '
!
~ 1
,
' '
1
' ' 1 M 1 ^ i I ! 1 ' 1
I ' 1 ■ '
1
(,
; 1 1
1 ' ' ' ' '
■ 1
i 1 !
. , 1 ! I ); 1 M j ; 1 1
1 1 i ' ' ' i ' ■
'Mi 1 ! I ! M
Q (
y 1 r
' ' ; ' '
y\\
7i
' 1 1
■ ' ' !
11'! Ill MM 1
I'M 1 M M 1 ' ' '
1 '
• 1 1
■ 1 . 1
M ' M 1 ' 1 ' '
' . ' '
i
J :iii.
' 1 1
, ■ '
i 1 i ' i 1 ' '
1 ' 1 1 ! j ; 1 1 ■ '
■ . ,
1 1
1 ,
1 ■ ■
1 . ' ' ' ' 1 1 ' 1 '
M ' ! 1 1 ' .
■ 1
1 1 : ■ ' 1 I'll
Mi M '
* ' 1
ill 1 ! ' M
M ' 1
' ■ ■ ' ■ 1 ' ■ : i ' ' 1 i
1 1 1 1 1 ' : ' .1
' — • !
?
1 ' ' t 1 : ' ' '
■gllD !
1 ' 1
1 ! M 1 M :
.y
3
' '
Q^
E
' ■ ' ■ 1 ■ ■ 1 ' 1 1 1 1 I 1
1 M ' M ' '
2t» ■
c
■ ' ' ■ 1 ' 1 ■ ' ' ' 1
1 1 Mm
'•'/;[ M 1 !
1 1 1 'Ml 1 ,
<
... If 1 ! 1 , : i
' M Ml Ml
' ■ M ' . 1 ' ■ 1 1 1
1 1 M ' 1 M ' ; ■
Wl 1
c
; .
i ' ■ ' ' \ ' 1 i
. 1 1 1 Ml' 1 ■ ,
: . ■
■
' ' ' ' 1 i ' 1 i ' 1 1 '
1 1 1 i 1 j ■
1 ■ ■
<-^ hi
• "^
' — -
|—
^ : ' i : M M ^
- M i i -1 — r-t~ 1 M 1 -r"
-^^
*■
■ ; ■ , /' ■ 1 ■ 1 1 ' ; i '
1 M 1 1 1 ' 1 ' '
«l>^
i CN
1— '
3
' 1 ,'/■■; 1 ' . I 1 ; 1
i M 1 M • M 1 '
IZH
3 ri -^
■
__!_: 1_
■: . . • , ■ 1 i M , 1 1 ; 1 M I
-Mil MM ' ! 1 '■ — 1-
E a -
:_
—
. _j„ ■
— ^ — ' M ! ' i ! ^1-
i
^ LU
< 5 -^
": :."r._i:i:
.7::: 11
~:z../":lz:z::'j.
-::i--£::r-!^±ny
- M ! I'M- — — -' — ' — 1
-o 1
^ " i
u < _
0 = r
_ „_ ___,
-llTZ
i
!- ~A- - M , ' —
.iA _j
"'-"""■"!
- ^— — M : i
:zi~
0
^1-
:I~i
1 ^ '
--ll--f^ 'l^j^
— ' \ \ ■ ^ — < !
1
i—zniiiiz—
E:;iHz^l^^d^-
_ ■ 1 ■ - .
'« !
; i —
--^^f"—
z:
—- ^^ rr—
-- — -^ — H"" '
^-^
LIJ /S r: .
— ^-
1
N^
— J ^ QC iU
/
j
—
-; ^_
:^3E^-
' ; ' 1
>
o
i , ;
- - ' , - — ~ 1
-s •
t-£" ;i::z;p^EF:E
_| : ,
f\J
^
1
o
1
i "■" i
-^ ._..L ._.:["" ' T- "_ ! 1 _ _
. 1
___.:+--—:!
-■ ■
-| L .
1
!
1 1
Q^
. DQ'Oin nn-r
]( T ■ nn-r
1 —
ig nn-nh
O
1
i 2
OIX)
ms is-mM bU3Hs"
500
i
< ■ ■ ■ 1 ■ ■ ■ : ■ ■ t ■ 1
" ■ . ! ! ■-
T"
. -..| .... ._!_ _ i
1 1 LU-
1 1 1
I — 1
-W
^ . 1 1 1
^_a_^_ :
OROVILLE DAM - MAXIMUM SECTION PROGRAM = QUAD 4
K2MAX = 130 LOWER CORE MODULUS
1 ^
_ _ _j . 1 :
^ . .- _„ : _„ ^
-o
ibH r 1 ' -+' -^ — -
_oa
, !
2--±^^ — _^^ — J-...
iTzir
1 ! ' ; 1 '' ■ '
' ■ 1
-o 1
-1- — ' r 1 — —
^^^r-—— i ' . 1 ' : ■ ! i 1 1 i ; ! — — — 1
-s
__.^ -r : ' ' ' ' , . ' ■ ' '
tzzt
- — -r — -t^,~~\i±
•^ -— — ^^ ! i i j ' i ' 1 , i i 1 —^ ^—
^i: :l:! MiThl'i IM i::i -
=1:=-^
O 1 ' ■ i 1 ! : : ^
^ III' M 1 ' ^ ' 1 ! ' 1 ' ' . ; 1
'^^ ' ' ■ ' 'i 1 ! ' 1 i M ' 1 ' 1 1
■ 1 1 . ' ■ ■ , ■ '
' '
D
' '
M *"
-T ! M ! i i ' ■ ■ ■ ' 1 ■ , ^ !
! ( 1 *^ M i ' 1 ! ' ' ■ i 1 I 1 ; ' i 1 '
3 ■
^ 1 1 ' ' ' 1 ■ ^ ' 1 ■ i ' ' ' . , 1 ,
Jj -H- 1 1 ' i i 1 1 i . i ' 1 ■
! ' . ■
' i 1
■
' ' ' ' ! t 1 I ' 1 I 1 ' 1 ' \ \ \
■ ■
cr i i ! I ' ' ■ • i ' ' ' ■^~— _x
; ; : 1 : : ; ■ , i ; i | | 1 ■ 1 i i | ; , i i
*Z ! i ' i i ' ; ■ ■ ■ ' 1 ' i ■ ^^-i-
1 :
-> 1 . i-]-r^ i ; -■ ' \ ^— 1 ^ ' ■ : 1 —
T^ 1 ' ■■ ; ; 1 ; : 1 i 1 , ' ■ i ■
n^. — t"^ — ' — ' ^ — ^ ' ■ : — 11'! — ; ' : — ! i 1 ,
^—
-Q
Zj 1 1 1 1 ' ■ ' ; ' — ' > '' ' 1 • 1 ' \ '■ , ' 1
i/l ' 1 ] 1 ' '. \ ■ ' 1 ' 1 i ' ' 1 ' '
i-»*i
J ■■ ' 1 ' 1 ! ' ' 1 ' 1 ' ' ' 1
I If !
•f ' ■ ' ' '■ 1 1 ' ' 1 ' 1 1 ■ ' ■ ' ! ' i
.
^ 1 i ' ■ ■ ' ' • .■:':.
■f^ ' ■ ■ ' 1 ' ' ' ' ' " 1 ' i
u ' ' ' ' ' i i ' ' ■ i i 1 1 1 * ' ' ■ i
Cj , ; 1 i ' ' ' 1 ' '
1 ' '
j< '■ \ ' ■ ' 1 ! 1 ' ' 1 ' ' ' : ' '■ I
s. 1 ■ 1 i 1 1 1 i 1 ■ 1 '
1 1 : ■
'
■^ 11 1 1 i 1 ' 1 , 1 , ■ \ . • , \ ', ^
J ! ' ! 1 ' ! 1 1 ' I ■ '
_, I i 1 Mill: M ' 1 ' t 1 : i i M 1 1
X 1 1 i ! 1 1 ' 1 1
'•~*
y\\ 1 ' ' ' ' ' i ' ' '
< \' i i 1 1 t ■ : : ; 1 , '■ , 1 1 f : I
1 ,
C3 ( 1
-* i i ' 1 ■ ' : ■ i , ' ■ ' : !
' ■ ■ . 1 1 " 1 ! ! 1 M ■ . : .
' . ■
'r~< l^
^ 1 1 1 ; 1 1 : . 1 ■ ' . !■ • '
I'll M 1 ■ ■ i ' 1 i : ■ :
•^ t)
3 ^^-t"- ^^^^^ ■'!■ ' 1 "7^
-^ --^ — - -: ; ^-| — M-^ ^— 1 — rk— ; i ■ j
ClJ
5 ^-f-+ -h-44-r- ! ' ' ^ ' i -rL-H-U^
1 1 ! ■
-t-pi —
1 j ; !
— ^
UJ -t -T- ' M : -H'tr^fi ^, ; ; •
•^ r-ti hH-^ — 1— i 1 : ' • M --p^
-^^i^isi^^^
' 1 ' '
.CD ""^
_...ir--
O II — 1+ ' 1 1 1 1 1 1 n 1 111 ^1 — ^
; : : : : ! ! , 1 1 1 i ; : : 1 ' i ! 1 1 ' ! ; ;
■ ■ 1
S J_ 1 ' ' ' ' I ' ' i i ' 1 1 1 '
fr OS ' 1 M [ 1 ! ' i j 1 ' i ,
' , ~^''"^-- 1.^ ! 1 1 i ■ ' 1 ' 1 ' 1 1 ! 1
1 ■
a UJ : III': 1 ! ! ' . ■
1 ! ; "^ ' ' ; 'i i i i i ■' ! i i ! 1 ; ' ' i
2
■*-£■ 1 !', '!l,>
-+' ■ ' ' \ ' ' 1 ' j ' ! , ■ ■ '
o
UJ •<• 1 i y
! ' ' ' I ' 1 ' 1 ' ' ' ' I
' ' 1
D . Ci
' ' ' 1 1 ! i ' 1 1 1 M ' ' ' '
to ^ ...... '■>
■ 1 ' 1 ■ 1 ' 1 1 ■
S- L! ! M 1 i 1 1
1 I ; ;
^1- ' 1 ' '
' ' M ~-H--u^ 1 M 1 1 '
'
-! z— Li-4^i---li-^-^^
-:4:^^^-^^-^---j± 1 ' V
< !^-_^V^--^--^-^-4^^ —
M-^
<r m 1 r ' "^ — —^-'. !_i
-f--u~r ' ! ' " — — r^^ ' 1 '"
1 i '
TuT'i,~'^ ■ "^ '
M
; , ■
OC UJ -"iji H^i; -+-
; M
! , ■ ■
1 >— -^ ' ' 1 '
' 1
1 ' ' i
](■ \ ^ ' 1 i ' ! ■
,
1 1
! , ■ 1 ' •
j
i ' ■ ' ■
i
1 1 M 1
g
-------------^----t'-^.x^—
■^ —^--4- -+ 1 ' ' i ! ^+
^
:: +- +■■ 1 1 ' i r* ^
- -±±t-------±^^\i^-4^lU-
; ' i '
1 M
1 i ^Tt~t^
1 1 '
1 1 1 1
1 ; ■
It it [ ^ji
' 1 '
: 1
1 ■ '
R ' ,
^^ 1 j
! !
M , '
4-
-htr
rr
1 1 i 1
T it "1 i;'"it2it i^M
^^Ltll: Jl3=r*' it it
1
' '
L
_U-U 1 1 1 1 T \
, I
502
503
-^' .',
-rj_j:t:
±~t~
'szr~z:z-
---4"---
___^
; i ' :
_^_..
_J-L-^.
1 1 i '
' ' 1
-^^
' ' ! '
4^^
-n^
! M '
^--r-
' ' ■ 1
__I-Z_
::_::::i
■ 1 , : ~
ZC^Z-'t^-IZ.
-.-^^
Vr'l-
■ 1 ■ ;
-! 1 i
• 1 1 1
1 1 ' '
i 1 i
Mm
— —
-^
rS
"1
bi' —
, .^
->' ;
-^J
-^^1_
OROVILLE DAM - MAXIMUM SECTION PROGRAM = QUAD 4
K2MAX = 130 LOWER CORE MODULUS
REANALYSIS EARTHQUAKE-AAAXIMUM ACCELERATION = 0.6g
1 j__
— — -7-
-^^^
--^-
— —
, , ,l^
1
~H — ' ; : '
-. — -
__
f—
4_ — ,
R^ 1
— ^ —
-T^-^
'
0 1
-~-.-
-'—
- —
;^^
■12 — 1
—^-
1 : ' r
^-^^^
~r^
--i—
- — — 1
1 ' i ' ■
' LL^-
1 ' ■ I
' ! • 1
■ 1 T r
MM
1 —
-j^n
j
"ii ' 1 i
1 1
' 1 '
I
-I- XV '
, '
' 1 '
Ml
-^ '
I 1 i 1
i
; 1
0
1 ; 1 r^
■ j
' M '
,1
'
0
^^^
! 1
"1 ; ]
::=i=i=^
J' ' '
1 i 1 '
! i i !
■ 1
•^ — 1
— — ^-^t—
1 , 1
, ■ j
=^—
;
.1 1 1
'
'
III'
■ 1 1
3 '
>-+^'
' ; ' '
' ' 1 '
S '
' 1 ' 1 ■
\ 1 '
' 1 1 :
' ' '
' ' ■ M [
' 1 ' '
-'"'-h^
; ' i ' ' 1
' ■;
"■
1
•■' '
' • ' .
'Z'
1
1 , ' 1 ' 1 '
i ' .
-r>': :
j
^^
; ; ;-
tr^
■
: , , : ,
Mil
. , , ,1
\^'
>—
M — [
^^
' 1 ,
'
X
J
/
i
,
—A
^— ^-
— h^
^— H
-^ —
— s^
^
■
-
^^-
— -~
— -t^
^
13-
tlj-
__^
"^
{'
, 1
J
Sty '
.^
r^
_^_>
mr; i
.^"^
f— 1
1
■'~^.,^
— ^
^ ! .
' ■
^^
(
'X
1
— ^ i ' '
1 ' 1 :
^^..^
r^
-0 —
-e
D
— —— <
" — ■
la
r . .
1 ' (
— —[-
^~*—-
K-..^^' ■
— — ^
" '
; i ' •
'^•^
1
! ■ ,
' . '
1 : 1
1 j
I'll
1 1 ■
'
J ~__4
I '
■ '
' 1 ' '
' !j
_2,^
— .— =
^^^ti:^
!
—
-Q
. . .
-^
III
' ' '
11
rf
J ^— ^
— j
—
III
1 ' '
1 ; : 1
~T^'
1
1
_—- — j-"^
!
1 11'
■
- ■ r<;
' 1
!
'
1 '
! 1 1
S
ii
1 1
.
'
■ '
'
f\i
1
' ■
' 1 ■
■ ■
' 1
< 1 1 1
[
i I'M
' 1 '
1 ' '
\
1 1 1
1 1 '
'
1 ' 1
;
'
■ ■ ■ A
' 1 1
1 1
' 1 1
! '
!
' 1 1 ■
i 1
; 1 ' !
1 '
1 ; . 1
' 1 ■
35(5
J-U
1
1
-t-L.. , 1
i-^
^^^
r^.
no'i
l±Xt
iiin
^{T^m
ijij'ai
4Hty-
JlllTll
- : :
[iirij,*:
'-—
OTj-ng
-0
d
504
505
506
507
508
509
00-091
510
:j:::m^4a----]=:DC-V
iQD'osi:--
511
512
513
514
515
o
<
^
O
II
</)
O)
:S
3
>o
<
3
fV
O
o
u
UJ
Z
g
Ul
0£.
^
Q-
o
U
IJU
0£
UJ
UJ
U
z
^
<
o
o
^
516
517
Q
<
3
o
II
«/j o>
^^-^
<Sm
OG
E MC
TION
Q. O 0^
U ^
C^ lU
lu U
^.^.<
O^ :?
h= i
U ^
LU X
to <
^
^ ^
i 1
II
< fc
UJ
^ <
, O
~)
CO to
z
1-
-< ^ CO
< II >
< X <
z
Q < Z
-?
,. . ^ <
UJ
LU CN UJ
—1
1 ^^ Oi
UJ
>
o
o^
O
oo'ogi
00'02I
518
iDtniEir
519
520
521
522
o <
IS |(/5
liJ V Q ^
O (T O W
O CE O OT
523
^
N_
A ' '-
1
____
[ ^^
\
V-
\
\
\
— D
o o
— Q)
3: >-
o
0) u
E
— 3
I- o
_l
524
NODE 4
0.50
4.0 8.0 12 0 16.0
TIME IN SECOND
LUSH RESPONSE ANALYSIS
20.0
-0.50
4.0 8.0 12.0 16.0
TIME IN SECOND
QUAD 4 RESPONSE ANALYSIS
20.0
Figure E-'tS. Comparisons of Acceleration Responses between LUSH and (iLIAD4
Analyses of Section 2 Using K„ =130 and Low Core Modulus
^ 2 max
525
OROVILLE DAM - SECTION 3
REANALYSIS EARTHQUAKE - MAXIMUM ACCELERATION
LUSH DYNAMIC RESPONSE ANALYSIS
SHELL K o = 130
0.6 g
CORE
2 max
G max -2200 (LOW CORE MODULUS)
Figure E-^?. Maximum Horizontal Shear Stresses, x , from LUSH Analysis of
Section 3 (tsf) ^^
OROVILLE DAM -SECTION 3
REANALYSIS EARTHQUAKE - MAXIMUM ACCELERATION = 0.6 g
LUSH DYNAMIC RESPONSE ANALYSIS
SHELL K « = 130
CORE
2 mox
G max
2200 (LOW CORE MODULUS)
Figure E-48. Maximum Shear Strains, Ymax, from LUSH Analysis of Section 3
Using K„ =130 and Low Core Modulus (percent)
i- max "^
526
rf-
T
0) 3
— -a
«- o
o 2:
— L.
DC O
E 3
— O
*J
0
10
c*\
S-
OJ
II
(U
Q. cn
>- c
I- —
527
OROVILLE DAM- SECTION 3
REANALYSIS E ARTH OU AK E - M AX I MU M ACC ELER ATION = 0.6g
QUAD 4 DYNAMIC RESPONSE ANALYSIS
SHELL K2 mox = '30
CORE
2200 (LOW CORE MODULUS)
St^.^M%^
"^
^^.19i^65i.95\1.08\.
^^1.35 /1.55ib.90\ 1.91 "~~v^
j,^r,k 1.77 11.97/1.12 \ i.ee i|.>,..
..-^1.85
1.62 12.51 J 1.21 2.07
2.13--^
^-^.B&
1.87
2.14 ^.Hl/l. 103; 1 2.21
2.51 "^
-<rT5
1.37
2.66
2.73 *i5)/ 1.11 l/l 2.90
J-58 /."SJ^
.^
1.16
2.39
2.80
1.27/ 1.S5 /s8
3.19
3.21
••96 ^^
^O;,i^0.98 1
1.*
2.10
li-Vi yi.zx / i.ei^^fj^.n
3.98
3.11
2.60 [ 1.39^^
Maximum Horizontal Shear Stresses, x , from QUAD^ Analysis of
Section 3 Using K^ ^3^ = '30 and Low Core Modulus^
Figure E-50.
OROVILLE DAM - SECTION 3
REANALYSIS E ARTHQU AK E - M AXI MUM ACC ELE R AT ION = 0.6 g
QUAD 4 DYNAMIC RESPONSE ANALYSIS
SHELL K2 ^Q, =130
G max
CORE
-- 2200 (LOW CORE MODULUS)
Figure E-5I . Maximum Strains, y . from QUAD^ Analysis of Section 3
Usinq K., =130 and Low Core Modulus
^ 2 max
528
529
NODE 4
0.50
-0.50
O50
0.50
-0.50
0.50
-0.50
tililiiiiliyiliiiiJil
4.0 8.0 12.0 16.0 20.0
TIME IN SECOND
LUSH RESPONSE ANALYSIS
4.0 8.0 12.0 16.0 20
TIME IN SECOND
QUAD 4 RESPONSE ANALYSIS
Figure E-53. Comparisons of Acceleration Responses Between LUSH and QUAD^
Analyses of Section 3 Using K- =130 and Low Cora Modulus
530
V
/1.3S
-^
0.13
1.21
0.99\
o.w\
cry
( V --
0.49/0,30
o-y (V=0.30)
0.T6 1
0.S7
8.09
0.99
0.60
o.so
O.SO
2.3S
l.OB
0.99
i.^\
X
o.n
a.9^
0.63 1
0.19
8.09
1.11
1.00
l.Ok
1.0l\^
^
1.18
0.9?
O.M
0.91 1
O.T
J. 01
I. IS
1.01
1.03
1.01
i.ooN^
y^.°D
1.31
0.91
o.ex
0.79
i.ie yo.33
i.as
i.n
l.OS
1.03
1.01
0.97
o.»\
MAXIMUM VERTICAL NORMAL STRESS (cTy )
yX.\Z
y^^
V
/1.25
0.80
0.85
0.90\
0.95\
Ux
I 1/ -
u.ts
/ U.
^.5«
(T, (V
= 0.30 )
0.61
0.67
0.39
0.90
0.70
0.68
0.87
0.93
0.98
0.94
i.oiN^
o.as
1.09
1.17
0.V8
O.Sl
0.94
0.98
1.00
i.rox^
1.13
1.86
1.39
1.S8
O.SU
0.71
l.OM
i.oe
1.01
1.01
i.»\
yLa
1. 67
l.Sl
1.63
1.86
8.« 1
0.119
1.06
1.17
1.07
1.03
l.Ol
1.03
sk^
MAXIMUM HORIZONTAL NORMAL STRESS ( cr^ )
Txy (V= 0.49/0.30)
MAXIMUM HORIZONTAL SHEAR STRESS (T^y )
LUSH DYNAMIC RESPONSE ANALYSIS
REANALYSIS EARTHQUAKE — MAXIMUM ACCELERATION =0.6g
EMBANKMENT K
2 MAX
130
Figure E-S'*. Effect of Polsson's Ratio on the Induced Dynamic Stresses in
the Model Embankment
531
V
y\.\a
^X^
0.79
o.w
o.g7\^
1.06\
CTy
(1/
= 0.45)
0.92
0.8E
0.61
0.76
0-y (1/
-- 0.30)
0.8S
0.83 1 0.91
0.56
0.78
0.89
l.lli\^
^
0.94
0.82
0.87
0.9*
0.S3
0.82
0.86
1.03
1.13\^
yO&
1.05
0.86
0.83
0.91
0.*
9. 47
0.90
0.89
0.94
1.11
i.oi\
y<yB3
1. 11
0.9S
0.87
o.et
0.98 1.03
1 1
O.W
0.99
0.9J
0.93
0.9S
1.20
0.93^
MAXIMUM VERTICAL NORMAL STRESS (cTy)
MAXIMUM HORIZONTAL NORMAL STRESS (crj
V
/
1.02
0.98
o.*\
0.37\^
r^y (T -- 0,45)
y^Oi
ya.in
/^.99
1.03 1
1.06
l.OB
1.05
Txy (1/ = 0.30)
l.tN
1.06 1
1.11
l.Il
1.10
1.08
i.re\
yyi.'S
1.08
1.06
l.OE 1
1.13
1.12
1. 10
1.07
1.09
1.12~\
yX.aa
t.ll
1.09
1.06
1.00 1
1.02
l.CK
l.CK
1.07
1.09
l.W
l.lii\^
/^tCoe
1.01
1.01
1. 00
0.97
0.92
0.93
0.93
0.93
0.95
1.01
1.03
l.CH
i.iJN..
MAXIMUM HORIZONTAL SHEAR STRESS (T*„)
LUSH DYNAMIC RESPONSE ANALYSIS
REANALYSIS EARTHQUAKE — MAXIMUM ACCELERATION =0.6g
EMBANKMENT K
2 MAX
= 130
Figure E-55. Effect of Poisson's Ration on the Induced Dynamic Stresses in
the Model Embankment.
532
APPENDIX F
EMBANKMENT RESPONSE MODEL
533
APPENDIX F
EMBANKMENT RESPONSE MODEL
As described previously in the main text, the
Embankment Response Model is a two— dimensional plane strain
analysis with a modified K„ (pseudo K„ ) value. This
2 max '^ 2 max
model was developed to account for the three— dimensional effect
of the canyon on the dynamic response of the embankment.
Oroville Dam is located in a triangular-shaped
canyon and has a variable cross-section (Figure F— l). In a
two— dimensional plane strain analysis, the length of the dam
(z— axis) is assumed to be infinite and all of the stresses
induced to resist movement are in the x-y plane (Figure F-2).
However, the abutments impart a restraining effect which gives
additional stiffness to the embankment. This additional stiffness
results from stresses in the y— z and x— z planes. Stresses in
these two planes are not accounted for in a two— dimensional plane
strain analysis.
In an attempt to simulate three— dimensional response,
an artifically-high (pseudo) K„ was used to account for the
'^ 2 max
stresses in the y-z and x-z planes. As detailed in Section 5,
a value of 350 was developed for the pseudo K„ value. This
^ ^2 max
value was determined from analyses of embankment response to the
1975 Oroville Earthquakes. In extending this model for use with
the Reanalysis Earthquake, it is assumed that the model can
simulate three— dimensional embankment response to earthquakes
of varying magnitude and frequency content.
535
Figure F-1. Three-dimensional Problem
Figure F-2. Two-dimensional Plane Strain Representation
536
In applying the model, it is assiojtned that the model
will simulate the three-dimensional response of the maximiim
section of the dam in the x-y plane. This means that the
accelerations and displacements would be approximated. However,
the shear stresses in the x— y plane would not be correct. This
is due to the fact that all of the dynamic stresses have essentially
been Itmiped together into the x-y plane by using the two-dimensional
plane strain analysis with a pseudo K„ value of 350. Since the
2 max
earthquake-induced shear stresses are of considerable importance
in a dynamic analysis of an embankment, the stresses must be
estimated in a different manner.
The method which was adopted to estimate the shear
stresses in the x-y plane resulting from a three— dimensional
embankment response assumed that the Embankment Response Model
approximated the correct shear strains in the x-y plane. Using
these shear strains, and the best estimate of the actual K„
2 max
value for the Oroville gravel, the horizontal shear stresses in
the x-y plane were estimated.
The procedure is detailed in the following equations:
t = Y * G (1)
where ^ = Shear Stress
^ = Shear Strain
G = Shear Modulus
G = R^ * K^ * ( Q' ')^'^ * 1000 (2)
d 2 max m
where R = Shear Modulus Reduction Factor, Dependent
Upon Shear Strain
^T = Effective Mean Normal Stress in psf
1' = ^ * R , * K„ * ( T )'^ * 1000 (3)
d 2 max m
537
Usine the Embankment Response Model and the pseudo K„
^ ^ 2 max
value of 350:
^/^^
= y * R^ * 350 * (CT')" * 1000 (k)
350 ^''350
The actual shear stress in the x— y plane induced in
a three— dimensional response would be computed using the actual
value of K„ for the gravel. As discussed previously, the
2 max ° f J ■:
best estimate of the actual K„ value is about l65. A
2 max
comparison of the actual and pseudo K values plotted against
shear strain is presented in Figure F— 3« The actual shear
stress in the x— y plane would be defined by:
Z = ^' ^ R^ * 165 * ( Cr')'^ * 1000 (5)
^^30 ^^30 ^
Assuming that the actual (3D) shear strains in the x-y
plane are approximated by the strains produced in the Embankment
Response Model,
y = ^ (6)
''''3D =^20^3^
^=^3D ' "-V2D "^ *'''*' ^-'^ * "'°° *"
Because the shear modulus reduction factor (R,) and the initial
d
effective mean normal stress ( ) are the same, equations k
m
and 7 may be combined to yield:
t = i65 * X (8)
^^30 350 ^YsD
350
538
I
This approach employs many assiimptions and has inherent
limitations. However, it is considered to model the actual
embankment response more accurately than the traditional plane
strain analysis using actual material properties.
539
540
APPENDIX G
CYCLIC TRIAXIAL TEST SUMMARIES
OF MODELED OROVILLE GRAVEL TESTS
(FIGS. G-1 THROUGH G-6 8)
541
APPENDIX G
CYCLIC TEST SUMMARIES
In order to present the test behavior of the cyclic
triaxial tests carried out for the modeled Oroville gravel,
cyclic test summaries were prepared. These summaries show the
peak values of cyclic deviator stress, pore water pressure
increase, and axial strain, plotted against cyclic number.
The test summaries are derived from the cyclic test
records and show uncorrected test behavior. Before utilizing
this information, corrections for membrane compliance, calibra-
tion error, membrane strength, and consolidation conditions (C )
should be applied.
Cyclic deviator stress peaks in the extension direction
are considered negative and are labeled so. Cyclic deviator
stress peaks in the compression direction are considered positive,
The sign convention for axial strain is also defined as having
compression being the positive direction. The strain peak
envelopes, however, are labeled with either "extensive" or
"compression" to identify the direction of the stress pulse
when the strain peak occurred.
The peak values of pore pressure increase were plotted
by using the back pressure value as a zero point. A value above
the back pressure was denoted as positive and a value below the
back pressure was denoted as negative. Also shown in the pore
water pressure summaries as a horizontal dashed line is the
initial effective confining pressure. Pore pressure envelopes
543
rising above this line show either incorrect calibration or
a change in the triaxial cell pressure.
These summaries are only intended to illustrate the
general behavior of the samples during testing. For a more
detailed examination, the actual test records should be
consulted.
544
-15000
-10000-
-5000-
> b"
a
o
5000-
o
u 10000
15000
EXTENSION
COMPRESSION
-'>
5000
(/)
(/)
u
QC
a. ^
•
<
UJ
QC
O
a.
5000
y^
v^'
-'>
-5
-'-^
EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
-'-'
80
85
Figure G-1 . Cyclic Test Envelopes for Test No, 6 (a' = 4,100 psf, K^ = 1.0)
545
15000
-10000
5000-
5000
G toooo
15000
EXTENSION
COMPRESSION
I
^y
5000
5000
._/
-rJ^
>.^/'
-r-r
-15
-10-
-5
EXTENSION
COMPRESSION
20 30
NUMBER OF CYCLES
h-
^>
40 7 5 80
Figure G-2. Cyclic Test Envelopes for Test No. 7 (a', = '^.lOO psf, K = 1.0)
jC c
546
-ISOOOr
-lOOOOh
I
I
5000-
< 0
> b'
Q
U
01-
5000 1-^
10000-
15000
EXTENSION
> /
I /
COMPRESSION
•t
-r>
50OOf
5000
-15
-lOl-
<<
10
EXTENSION
COMPRESSION
^y
10
20 30
NUMBER OF CYCLES
40
60
65
Figure G-3. Cyclic Test Envelopes for Test No. 10 (a' = 4,100 psf, K = 1.0)
jQ C
547
-ISOOOr
-10000- >
5000-
5000
10000
19000
EXTENSION
COMPRESSION
5000
a. 0
5000
1
s
\
\
1
\
/
■H
X LOWER
PORE PRESSURE ENVELOPE BEYOND RECORDING LIMITS
-5-
EXTENSION
COMPRESSION
5 -
20 30
NUMBER OF CYCLES
40
Figure G-^. Cyclic Test Envelopes for Test No, 11 (a'^^ = 4,100 psf, K^ = l.O)
5A8
-ISOOOr
-toooo-
-5000-
O S
9000-
o
U 10000
15000
EXTENSION
COMPRESSION
50O0
5000
-15
-10-
JS
-
y
/
^
"
-
-
EXTENSION
y
N
-
-
-
-
"compression
1 1
1 I—
K)
20 30
NUMBER OF CYCLES
40
50
Figure G-5. Cyclic Test Envelopes for Test No. 12 (o' = ^4,100 psf, K = l.O)
jC c
549
-ISOOOr
-100O0-
5000-
> b'
Q
U
_l
o
>-
u
5000
10000
15000
EXTENSION
COMPRESSION
5000
-5000
a5
-15
-10
-5
5-
10
EXTENSION
\
COMPRESSION
U
*COMPRESSION STRAIN ENVELOPE
BEYOND RECORDING LIMITS
10
20 50
NUMBER OF CYCLES
40
50
Figure G-6. Cyclic Test Envelopes for Test No. 13 (°', = ^,100 psf, K = 1.5)
jO c
550
-15000
^ -10000^
Vi
5000-
q: ^
< a
> b'
Q
<J
_l
O
01-
soooi-
10000-
15000
EXTENSION
COMPRESSION
5000
-5000
W o^
-15
-10
-5
10
EXTENSION
COMPRESSION ~~ — — _^
__l I 111= L
10
20 30
NUMBER OF CYCLES
40
50
Figure G-7. Cyclic Test Envelopes for Test No. 14 i°' ^^ = 4,100 psf, K^ = 1.5)
551
-ISOOOr
-10000-
5000-
Ui
o
u
5000
u
u 10000
15000
EXTENSION
COMPRESSION
5000
(A
M
UJ
(T
a. ^
-5000
<
-15
-10-
5-
10
."Zl-n.-:--- EXTENSION
COMPRESSION
10
20 K>
MUMKR OF CYCLES
40
50
Figure G-8. Cyclic Test Envelopes for Test No. 15 (o' = 4,100 psf, K = 2.0)
ic c
552
-ISOOOr
-10000-
-5000-
> b'
UJ
o
u
5000
10000
15000
EXTENSION
COMPRESSION
5000
5000
.'■"N
/
/
1
*
* LOWER PORE PRESSURE ENVELOPE BEYOND RECORDING LIMITS
<
ct
CO »^
-10-
-5
5-
IQ
EXTENSION
y
COMPRESSION
10
20 30
^4UMBER OF CYCLES
40
50
Figure G-9. Cyclic Test Envelopes for Test No. I6 (cf'^^ = 4,100 psf, K^. = l.O)
553
-ISOOOr
-10000-
-5000-
> b"
u
o
o
-I
>-
o
50O0-
10000-
15000
EXTENSION
COMPRESSION
-N'
5000
a
^
.^
0
-5000
^^'^
-'i-
-15
-10
-5
5-
10
__EXTE_NSION
COMPRESSION
K)
20 30
NUMBER OF CYCLES
40j
-'-'
50 55
Figure G-10. Cyclic Test Envelopes for Test No. 17 ( «^ , = 4,100 psf, K = 1.5)
554
-iSOOOr
-fOOOO-
5000-
O •
> b"
5000-
10000-
ISOOO
r
EXTENSION
COMPRESSION
5000
5000
z
<
-15
-10-
-5-
5-
10
EXTENSION
COMPRESSION
I
1
L 1
10
20 30
NUMBER OF CYCLES
40
50
Figure G-11. Cyclic Test Envelopes for Test No. 18 io'^ = 4,100 psf, K^ = 2.0)
555
-i9000r
toooo-
-5000-
5000
10000
l»000
EXTENSION
*
COMPRESSION
*■ CYCLIC STRESS NOT RECORDED FIRST 17 CYCLES
UJ
ec
z>
«/)
i/>
UJ
tr
a. ^
m
<
5000
-50O0
~
1
1 y ^
\^^^
-15
-10
-5
10
■~" — ^—^ EXTENSION
COMPRESSION
20 30
NUMBER OF CYCLES
40
50
Figure G-12. Cyclic Test Envelopes for Test No. 19 (o' ^ = 4,100 psf, K^ = 2.0)
556
-I500O
to
-10000
V)
UJ
ac
^-
in
-sooo
cr
^
o
•
»-
<
0
>
b°
u
n
5000
o
.J
o
>-
u
10000
15000
EXTENSION
COMPRESSION
-T-r
5000
-50O0
/
/
/
/ X
/ /
/
-f-t '
-T-T
tn «"
-10 -
-, _ -^ ~ ~~ ^
__EXTENSION
compression" ~~ — -^ __
¥: Compression strain beyond recording limlls
I I L.
10
40
60 65
20 30
NUMBER OF CYCLES
Figure G-13. Cyclic Test Envelopes for Test No. 20 (a'^^ = A, 100 psf, K^ = 2.0)
557
-I50CX)
-lOOOO-
-5000-
< Q
> b"
Q
O
5CO0>-
G 10000-
19000
5000
-5000
<
*- -^
<
X
-15
-10
-5-
10
* COMPRESSION STRAIN
ENVELOPE
BEYOND
RECORDING
LIMITS
-
EXTENSION
"~"---^
-v-^^
COMPRESSION
1
— ^'"x
•^
1 ~~" ~~
* .
-^^_
10
40
50
20 30
NUMBER OF CYCLES
Figure G-14. Cyclic Test Envelopes for Test No. 22 (a' = ^,100 psf, K = 2.0)
558
ISOOCf-
< c
> b'
u
Q
-IOOOO>-
50001-
0(-
50O0^
G looooh
EXTENSION
COMPRESSION
iSOOOl
5CO0
5000
■^^
-15
-lOh * COMPRESSION STRAIN ENVELOPE BEYOND
RECORDING LIMITS
°k-— .-
5-
— EXTENSION
COMPRESSION
>-r
20 30
NUMBER OF CYCLES
40
<Z
¥^\ — •
60 65
Figure G-I5. Cyclic Test Envelopes for Test No. 23 (a', = 4,100 psf, K = 2.0)
559
-ISOOOr
-10000-
-5000-
»000
10000
15000
EXTENSION
COMPRESSION
-'>
UJ
cr
(/>
Ui
<
UJ
(T
O
Q.
5000
-5000
* PORE PRESSURE TRACES UNCERTAIN
-r>
-10
-5
10-
X — — ^_ EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
-L.
401
-'-^
55
60
Figure G-16. Cyclic Test Envelopes for Test No. 24 (a' = i*,100 psf K = 2 O)
3c "^ ' c
560
-19000
-10000-
5000-
< o
> b"
u
o
o
-J
o
>-
u
5000-
10000-
15000
EXTENSION
COMPRESSION
5000
z>
I/)
UJ
a ^
a: <k
UJ _
-5000
y "
/
1
1
f
^
* LOWER PORE PRESSURE ENVELOPE BEYOND RECORDING LIMITS
-10
-
-5
0
EXTENSION
f)
^ ^^COMPRESSION
in
1 1 ""-r i
10
20 30
NUMBER OF CYCLES
40
50
Figure G-17. Cyclic Test Envelopes for Test No. 25 (a', = ^,100 psf, K = 2.0)
jc c
561
-ISOOOr
-10000-
5000-
> b"
UJ
a
o
5OO0-
o
o lOOOO
I5000
--<
EXTENSION
COMPRESSION
-'>
5000
M
UJ
ir
5000
0<^
i^
-15
-10-
-5-
J
'
-
1
"^ —
1
EXTENSION
COMPRESSION
1
-=.
— ■=5
1 ,
0
10
20
30
40|
0.=T^
5-
Figure G-18.
10
NUMBER OF CYCLES
Cyclic Test Envelopes for Test No. 28 (a'
- = 4,100 psf, K = 2.0)
3c ' "^ ' c
562
-15000
M
hi
»-
CO
> b'
o
o
-10000-
5O00-
5000
10000-
I5O00
---'
EXTENSION
COMPRESSION
-%'
50O0
^'
-5000
/.- —
-'J'
aS
-15
-10-
-5
5-
10
-'V-
- extension
compression"
K)
40
125
130
20 30
NUMBER OF CYCLES
Figure G-19: Cyclic Test Envelopes for Test No. 29 (a', = '♦,100 psf, K = 1.5)
563
-15000
-10000-
- 5000 ~ ^ _ _ _
> b"
O
5000 =
o 10000
15000
.--'
EXTENSION
COMPRESSION
-'^'
5000
0
/
(
-5000
f>
-r-T
-5
5 -
10 -
>>
EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
4CH
135
140
Figure G-20. Cyclic Test Envelopes for Test No. 30 (a' = 4,100 psf, K = 2.0)
3c c
564
-60000
(O -40000
(/)
u
(T
J^ -20000-
O S
> kT
o
20000-
O 40000
600001
EXTENSION
COMPRESSION
30000
200OO
10000
-lOOOO
/
i
1
1
r
,^-''
^^'
--
^-^-^
^
1
I
/
M
-15
-10 -
ac -5
3?
5-
10,
/
/
^
^
EXTENSION
-~
-
-
-
-
—
~~
-.
-J
1
COMPRESSION
1 1
■^
^
_L
-
-
-
-
—
20 30
NUMBER OF CYCLES
40
50
Figure G-21 . Cyclic Test Envelopes for Test No. 33 (a', = 28,700 psf, K =1.0)
565
-60000
-40000
-20000
_ Q.
20000 -
40000 -
60000
EXTENSION
COMPRESSION
30000
20000 -
10000
-10000
-15
-10
-5-
5-
10,
EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-22. Cyclic Test Envelopes for Test No. 3^ (o'-, = 28.700 psf, K = l.O)
Jc c
566
-60000
-40000
a:
U) -20000
> b'
"^ 20000
O
O 40000
60000
EXTENSION
COMPRESSION
30000
20000 -
10000
-10000
(/) o^
I
-15
-10
-5-
5-
10.
EXTENSION
g I — . — -•— '
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-23. Cyclic Test Envelopes for Test No. 35 (a' ^ =28,700 psf, K^ = l.O)
i
58—78786
567
-60000
-40000-
(A
I;; -20000
20000
40000
60000
EXTENSION
COMPRESSION
90000
UJ
c
Vi
0^ 20000
UJ
(T
/
(T <^ lOOOOM-
I
<
-10000
-15
9
IT
- 1
'extension
/
- /
/
COMPRESSION
_ 1 1 1 1
Ot^
5-
10
10
20 30
NUMBER OF CYCLES
40
Figure G-24, Cyclic Test Envelopes for Test No. 36 (a' = 28,700 psf, K = l.O)
Jc t
568
-eoooor
y, -40000J-
vt
UJ
^ -20000
IT «
> b'
UJ
o
- EXTENSION
20O0O
O
O 40000
60OO0
- COMPRESSION
30000
UJ
D
CO
«^ 20000
UJ
(T
a ^
cr <* 10000 -
-lOOOO
~-
_ /
/
/
_/
1
/
1
-15
-10
EXTENSION
/ /
/ ^COMPRESSION
/
10 20 30 40
NUMBER OF CYCLES
50
Figure G-25. Cyclic Test Envelopes for Test No. 37 (a' = 28,700 psf, K = l.O)
jC c
569
-6OO00
-40000-
;;; -zoooo-
2CXXX)-
40OO0-
600001
>-'
EXTENSION
COMPRESSION
-'-'
6CX>00
40000
20OO0
UJ
c
o
a
0-
-20000
<-
-15
-10-
-5-
-
^
EXTENSION
-
(
COMPRESSION
1
1
..
0
10
20
30
40
NUMBER OF CYCLES
330
Figure G-26. Cyclic Test Envelopes for Test No. 38 ( a' = 53,300 psf, K =1.0)
^C c
570
Vi
-60000
-40000J-
ui
<r
M -20000-
P •
> k'
UI
o
200001-
_i
u
U 40000
•0000^
EXTENSION
COMPRESSION
60000
-20000
-15
Z
I
/EXTENSION
'COMPRESSION
20 iO
NUMBER OF CYCLES
40
50
Figure G-27. Cyclic Test Envelopes for Test No. 39 ( a' = 53,300 psf, K =1.0)
jC c
571
-600C»
y, -400CX>t-
V)
III
<r
vi -20000-
p •
UJ
o
20O00-
u
O 40000
60000^
EXTENSION
COMPRESSION
60000
a
to
<^ 40O00
UJ
K
O. ^
M
Jt «^20000
-20000
Qt— -
-15
-10-
o:.
5 -
EXTENSION
COMPRESSION
20 X
NUMBER OF CYCLES
40
50
Figure G-28. Cyclic Test Envelopes for Test No. hO (a' = 53,300 psf, K =1.0)
jC c
572
-15000
-tOOOO-
5000-
O
5000 =
10000-
15000
EXTENSION
COMPRESSION
-'>
5000
0^
-5000
-f-r
jrJr
a?
-15
-10-
-5-
10,
10
>>
EXTENSION
COMPRESSION
20 30
NUMBER OF CYCLES
4CH
^'-^
100 105
Figure G-29. Cyclic Test Envelopes for Test No. k\ (a' = 4,100 psf, K^ = l.O)
573
-60000
y, -40000
Ui
w -20000-
O S
< e
> b'
Ui
o
_ EXTENSION
20000-
40O00
60000*.
- COMPRESSION
eocoo
40000-
^20000
-20000
-15
I
-10|- /
/
/
/
5-
10
'EXTENSION
/
f /compression
10
20 30
NUMBER OF CYCLES
40
50
Figure G-30. Cyclic Test Envelopes for Test No. kl (a' = 53,300 psf, K =1.0)
574
-60000
■40000-
-20000
O *
u
a
u
-J
u
>-
o
20000
40000
6O0O0
-'-'
EXTENSION
COMPRESSION
-.'-r
I
30000
20000 -
«^ toooo-
-10000
-'-r
-'-■'
z
cr
-15
-10-
-5-
5-
10
-
4
'
EXTENSION
COMPRESSION
~'^~
-
1
i i
1
0
10
20 30
40*
NUMBER OF CYCLES
440 445
Figure G-31 . Cyclic Test Envelopes for Test No. ^3 (a ' ^ = 28,700 psf, K * 2.0)
575
60000
■40O0O-
U
I;; -20000
IT „
> b'
UJ
20000
O 40000
60000
EXTENSION
COMPRESSION
30000cr
■10000
z
IT
*- >5
en «"
-15
-5
10
""*"— -.^ ^ — — — _^EXTEN
EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-32. Cyclic Test Envelopes for Test No. kk (a* = 28,700 psf, K = 2.0)
576
-60000
y, -40000f=^ —
(/)
U
a:
t5 -20OO0
> b'
UJ
20000-
40000 -
60000
EXTENSION
COMPRESSION
SOOOOcr
20000
o: * »OO00|L
UJ
-10000
9
-15
-10
-5
10
EXTENSION
^COMPRESSION
\ I
to
20 30
NUMBER OF CYCLES
40
50
Figure G-33. Cyclic Test Envelopes for Test No. ^5 ( o' = 28,700 psf, K = 2.0)
577
-•oooor
-40000-
-20000-
O S.
UJ
a
soooo
t> 40000
60000
EXTENSION
COMPRESSION
-10000
9
tr
-10
-5
10
EXTENSION
\
\
\
N
\
\
\
^^COMPRESSION
J ii_l L
10
20 90
NUMBER OF CYCLES
40
50
Figure G-34. Cyclic Test Envelopes for Test No. ^6 (0' = 28,700 psf, K = 2.0)
3c c
578
-ISOOOr
y, -looooH
-5000-
(T
^_
O
•
0
<
a.
>
b'
UJ
a
5000
o
_j
o
<_>
10000
15000
EXTENSION
COMPRESSION
-'-r
5000
Or
5000
if-h
/ ,
JTZ
-15
-10-
-5
5-
10
JrJr
EXTENSION
COMPRESSION
20 30
NUMBER OF CYCLES
401
350 355
Figure G-35. Cyclic Test Envelopes for Test No. kl (a' = 4,100 psf, K = l.O)
ic c
579
-60000
•40000-
-20000-
20000-
40000 -
60000
• EXTENSION
COMPRESSION
-10000
z
<r
■10
-5 -
EXTENSION
'^ COMPRESSION
\
\
10
20 30
NUMBER OF CYCLES
40
Figure G-36. Cyclic Test Envelopes for Test No. ^8 (a' ^ = 28,700 psf, K^ = 2.0)
580
-ISOOOf
-10000-
-5000-
9000
10000
19000
EXTENSION
.--■1
COMPRESSION
-'-'
UJ
(C
(A
(/)
UJ
IT
a ^
•
a: *
9000
9000
-'Jr
/
/
/
-'-r
a?
-15
-10
-5
10.
EXTENSION
0^
COMPRESSION
10
401
75
80
20 30
NUMBER OF CYCLES
Figure G-37. Cyclic Test Envelopes for Test No. 49 (a' ^ = 4,100 psf, K^ = 2.0)
581
-60OOO
-400OO-
M
UJ
(E
^ -20000
20000
40000 -
60000
EXTENSION
^'''
COMPRESSION
30000
20000
/
a: «^ 10000 H
-10000
''.'
-10
-5-
5-
10-
15
1
*
>^
1
~
—
__ EXTENSION
COMPRESSION
1 1
~
^
~
^
<
0
10
20 30
4<?
NUMBER OF CYCLES
Figure G-38. Cyclic Test Envelopes for Test No. 50 (a' =28,700 psf, K = 2.0)
582
-6O0O0
y, -40000-
UJ
a:
^ -20000}-
20000-
40000
600001
EXTENSION
COMPRESSION
60000
40000 f
'200O0
-20000
-10
-5-
10
la
N
EXTENSION
COMPRESSION
•0
40
50
20 30
NUMBER OF CYCLES
Figure G-39. Cyclic Test Envelopes for Test No. 51 (a' = 53,300 psf, K = 2.0)
583
-60000
y, -40000J-
</)
u
a:
V> -20000-
UJ
20000-
u
U 40000
eoooo^
EXTENSION
COMPRESSION
60000
40000
'20OO0
-20000*-
I
Ir-
-10
-5
10-
r::_-^____EXTENsiON
compression" ~~ -^"^^-=~-=-:r^-::_--__
X
a.
40
50
O K> 20 30
NUMBER OF CYCLES
Figure Q-kO. Cyclic Test Envelopes for Test No. 52 (a'3<- = 53,300 psf, K^ = 2.0)
58A
-75000
y, -50000
</)
UJ
a:
V) -25000|-
P •
UJ
o
25000
Sri
-t
O
O 50000
75000
EXTENSION
COMPRESSION
•oooo
-20000
15
N EXTENSION
to- xCOMPRESSION
10
40
50
20 30
NUMBEI^ OF CYCLES
Figure G-41 . Cyclic Test Envelopes for Test No. 53 (0*3^ = 53,300 psf, K^ = 2.0)
585
-60000
(^ -40000
\r) -20000
20000-
40000
60000^
EXTENSION
>*'
COMPRESSION
-'-'
60000
40OO0-
(£ '^ 20OO0 J,'
i*J , I,
-
-20000
>">
W o^
-5-
10-
^^-=i=~__ EXTENSION
20 30
NUMBER OF CYCLES
40
ISO
165
Figure G-42. Cyclic Test Envelopes for Test No. 55 (o ' , = 53,300 psf, K = 2.0)
jc c
586
-60000
-40000
-20000-
EXTENSION
600001
20000-
40000 - — 1— — „Tr:.T.
COMPRESSION
60000
y* 40000
20OO0
-20OO0
3?
-10
-5
15
v"^x
\ \ EXTENSION
u \ ^
\
\
N
\
COMPRESSION
_L
10
-L
-L
40
50
20 30
NUMBER OF CYCLES
Figure G-43. Cyclic Test Envelopes for Test No. 56 (a ' = 53,300 psf, K =1.5)
587
-60000
^ -40000
M -20000-
C
O
< o
> k'
UJ
o
y
o
20000-
40000
•0000^
EXTENSION
COMPRESSION
•oooo
40000
- /
^20000 4
-20000^
//"
-10
-5
10-
J.
— C~.C--^ ^_EXTENSION
COMPRESSION
X
O O 20 30
NUMBER OF CYCLES
Figure G-kk. Cyclic Test Envelopes for Test No. 57 (a'
40
50
3j. = 53,300 psf, K^ = 1.5)
588
-15000
-•0000-
-sooo-
5000-
10000
1 5000
EXTENSION
COMPRESSION
5000
5000
z
<
*- :5
Vi r
m
-J
<
X
<
-10
-5
10
15
EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-45. Cyclic Test Envelopes for Test No. 58 (a" = 4,100 psf, K = 2.0)
jC c
589
-coooo
y, -400001-
(/)
u
^ -20000-
p •
u
o
20000-
o 400OO
eoooo^
EXTENSION
COMPRESSION
eoooo
«^ 40000
^20000
-20OO0
-lU
-5
EXTENSION
0
^ ^^
-V
\ \
\
b
- \
\
\
\
10
\
\
IS
COMPRESSION
1 1 I L_ .
to
20 30
NUMBER OF CYCLES
40
50
Figure Q-kS. Cyclic Test Envelopes for Test No. 59 (a' = 53,300 psf, K =1.5)
jC c
590
-600O0
-40000-
(/>
Ui
oc
^ -20000
< *
2OO0O
G 40000
EXTENSION
COMPRESSION
60000^
-10000
i
EXTENSION
10
COMPRESSION
X
0 »
Figure G-47. Cyclic Test Envelopes
40
50
20 SO
NUMBCR OF CYCLES
for Test No. 60 (a ' ^^ = 28,700 psf, K^ = 1-5)
591
-•OOOOf
y, -40000-
Ui
c
I;; -20000
o s.
- *
> k
20000
O 4O000
•oooo
EXTENSION
COMPRESSION
-10000
10
-5-
9
10-
EXTENSION
COMPRESSION "^ ^
10
to 90
NUMBCR OF CYCLES
40
50
Figure Q-k8. Cyclic Test Envelopes for Test No. 61 (a' = 28,700 psf, K =1.5)
592
-60000
-40000-
-20000
20000
40000 -
EXTENSION
eoooo
COMPRESSION
-10000
-10
2 -=
10
|- /
/
/
EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure Q-kS. Cyclic Test Envelopes for Test No. 62 (o ' 3^ = 28,700 psf, K^ - 1.5)
593
-600O0
y, -40000h
(/)
ti -20000
> b'
UJ
o
20000-
O
O 40000
6OOO0
<,'-■'
EXTENSION
COMPRESSION
-'^r
30000
in
«« 20000
UJ
(T
a. ^
ac * looool- /
■10000
-"-'
z
i
10
-'-'
EXTENSION
z: __::..
COMPRESSION
10
20 30
NUMBER OF CYCLES
-'-''
40"
295 300
Figure G-50. Cyclic Test Envelopes for Test No. 63 (a' = 28,700 psf, K = 1.5)
594
-60000
-40000
-20000-
< e
> h°
a
20000-
40000-
60000*-
EXTENSION
>-'
COMPRESSION
-'.'
60000
4O0O0
'200O0
-20000
^->
/ /
1/
<-
t
EXTENION
COMPRESSION
to
40
-'-'
245
250
20 30
NUMBER OF CYCLES
Figure G-51. Cyclic Test Envelopes for Test No. 64 (a ' = 53,300 psf, K = 1.5)
^c t
595
-60000
-40000-
V)
UJ
(rt -zoooof-
< •
> b^
u
o
20000-
40000-
eoooo^
EXTENSION
COMPRESSION
ftOOOO
40000
•20000 f
-20000>-
^
-10
/extension
/
/
/
/
-5
0
/
/
■^^-^
compression
5
n
1 1 1 1
20 30
NUMBER OF CYCLES
40
50
Figure G-52. Cyclic Test Envelopes for Test No. 65 (a ' , = 53,300 psf, K =1.0)
^C c
596
-eoooo
y, -40000
UJ
EXTENSION
Jn -ZOOOOt- ■-
> b'
u
o
eooooL
zooooh
COMPRESSION
40000
60000
40000
'20O00
-20000
#
■10
/extension
/
/
/
/
— ^
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-53- Cyclic Test Envelopes for Test No. 66 (a ' ^^ = 53,300 psf, K^ = 1.0)
597
-6OO00
y, -40000h
V> -2000O-
P •
> kT
Ui
o
2CXXX)-
o
O 40000
600001
EXTENSION
COMPRESSION
-20000
-15
/EXTENSION
/ 'COMPRESSION
1/ '
5-
20 30
NUMBER Of CYCLES
40
Figure G-S'*. Cyclic Test Envelopes for Test No. 67 (a ' = 53,300 psf, K =1.0)
598
-60000
y, -40000
to
UJ
(T
^ -20000-
O 5
< c
> b^
UJ
o
20O0O-
40000
60000L
EXTENSION
COMPRESSION
60000
40000-
'20000
-20000^
-15
-10
-5
5-
10
EXTENSION
/COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-55. Cyclic Test Envelopes for Test No. 68 (a ' ,^ = 53,300 psf, K =
.0)
599
-60000
^r, -40000
UJ
(T
^ -20000-
O S
< c
> b'
UJ
o
20000-
u
O 40000
60000^
EXTENSION
- COMPRESSION
60000
-20O00
3?
-15
- (EXTENSION
COMPRESSION
20 30
NUMBER OF CYCLES
40
50
Figure G-56. Cyclic Test Envelopes for Test No. 69 (a' = 53,300 psf, K = l.O)
jC c
600
-60000
-40000-
(/>
UJ
^ -20000
2OOO0
40000
60000
EXTENSION
COMPRESSION
30000
^ 200O0 -
<
10000 4
-10000
-15
-10
-5
/
/
/ EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-57. Cyclic Test Envelopes for Test No. 70 (a' = 28,700 psf, K^ = 1.0)
601
-60000
-40000-
^ -20000 -
o £
< 0
> b"
UJ
a
20000
40000
60000
EXTENSION
COMPRESSION
30000rr
20000
10000
-10000
9
-10
-5
10-
EXTENSION
^
/ \
—^ \
* EXTENSION STRAIN BEYOND RECORDING
LIMITS AFTER CYCLE NO. 4
\
\ COMPRESSION
K)
20 30
NUMBER OF CYCLES
40
50
Figure G-58. Cyclic Test Envelopes for Test No. 71 (o', = 28,700 psf, K = 1.5)
3c
602
-ISOOOr
(A -KXX)Of-
UJ
K
t) -9000-
s •
O
9000-
u
u fOQOO
19000
EXTENSION
COMPRESSION
toooo
-20000*
-15
10 -
-5
& -
EXTENSION
COMPRESSION
10
40
50
to 90
NUMBER OF CYCLES
Figure G-59. Cyclic Test Envelopes for Test No. 72 (a ' ^ = 16,400 psf, K^ = l-O)
603
-15000
(rt -10000
to -SOOO
< c
> b'
UJ
o
5000-
o
O 10000
I5OO0
EXTENSION
COMPRESSION
20000
fn 10000 -f
-lOOOO
-20000
S5
-15
-10
-5
10
EXTENSION
£^
COMPRESSION
K)
20 30
NUMBER OF CYCLES
40
50
Figure G-60. Cyclic Test Envelopes for Test No. 73 (a ' , = 16,^00 psf, K =1.0)
jc c
604
-15000
-10000-
</)
V)
Ui
In -9000
5 1
9000
10000
19000
\ EXTENSION
\
\
.-^ COMPRESSION
-20000
-10
/ EXTENSION
COMPRESSIN
10
10
20 30
NUMBER OF CYCLES
40
50
Figure G-61 . Cyclic Test Envelopes for Test No. Jk (a ' ^^ = 16,^400 psf, K^ - l-O)
605
w -10000
UJ
c
^ -5000
Is
o
5000
(_>
-i
u
U 10000
-^ ^ EXTENSION
_- COMPRESSION
UJ 20000
c
(A
2 lOOOO
a.
-10000
-20O00
-15
-10 -
10
EXTENSION
COMPRESSION
5 -
10
20 30
NUMBER OF CYCLES
40
50
Figure G-62. Cyclic Test Envelopes for Test No. 75 (o ' = 16,^00 psf, K = l.O)
ic c
606
-15000
i/)
-10000
v>
UJ
IT
(O
-5000
g
•1
<
0
a
>
b^
UJ
o
5000
u
_)
o
o
lOOOO
I5OO0
-"'
- — ~ __ EXTENSION
COMPRESSION
-'-r
, , 20000
(T
J2 lOOOO
(T
a.
-KXXX)
-20000^
/ ^
-15
-I©--
W o-
10
-'-^
EXTENSION
COMPRESSION
20 30
NUMBER OF CYCLES
-'-'
40l I 90 95
Figure G-63. Cyclic Test Envelopes for Test No. 76 (a ' = 16,^00 psf, K = l.O)
607
o
o
-10000
-
-5000
i
_/" "* ^_
EXTENSION
.'*'
>
5000
-
COMPRESSION
■ " "'f 1
10000
-
15000
UJ
IT
13
M
(A
Ui
(T
a. ^
•
a: <^
5000
0<
5000
^'>
-'>
-W-
-5
5 -
10
-
^
^ ~
EXTENSION
1
COMPRESSION
1
1
~
-
-
1
0
10
20
30
40i
0, ^ __ __
^4UMB€R OF CYCLES
Figure G-Si*. Cyclic Test Envelopes for Test No. 77 (a ' = k ,\m psf, K =1.5)
^C c
608
-i5000r
-HOOOO-
■5000-
> b"
u
a
5000
o
o 10000
19000
^ EXTENSION
COMPRESSION
5000
D
(/)
to
u
cr
a.
IT
U
»-
<
a
o
a.
-5000
-10
EXTENSION
/
/
--^COMPRESSION
K)
20 30
NUMBER OF CYCLES
40
50
Figure G-65. Cyclic Test Envelopes for Test No. 78 (0*3^. = ^,'00 psf, K^ - 1-5)
609
-ISOOOr
-10000-
-5000-
tt «
O S
UJ
o
9000
10000
19000
EXTENSION
COMPRESSION
UJ
</>
M
UJ
5000
-5000
a?
-10
-5-
5-
10-
15
■ ^ EXTENSION
COMPRESSION
10
20 30
NUMBER OF CYCLES
40
50
Figure G-66. Cyclic Test Envelopes for Test No. 79 (a' = A , 1 00 psf, K =1.5)
jO c
610
-15000
-10000-
-50OO-
sr ^
< o
> b*
o
o
5000
o tOOOO
15000
EXTENSION
COMPRESSION
>>
y ■>^^ ^
5000
-5000
-f-r
-r-r
^ .^-
-15
-10-
10
.^ __EXTENSI0N
-'--
COMPRESSION
1^
105
Figure G-67. Cyc
10 20 30 401
NUMBER OF CYCLES
lie Test Envelopes for Test No. 80 (a ' 3^ = ^JOO psf, K^ = 1.5)
611
-ISOOO
w - toooo --
to -50001-
5 1
UJ
o
SOOO-
o
o KXXX)
I9000
EXTENSION
COMPRESSION
20000
-20000"-
-10 -
<
on
10
/ EXTENSION
COMPRESSION
K)
20 30
NUMBER OF CYCLES
40
50
Figure G-68. Cyclic Test Envelopes for Test No. 81 (a'
3c
16,400 psf, K = 1.0)
612
APPENDIX H
EXTRAPOLATION OF ISOTROPICALLY-CONSOLIDATED CYCLIC
TRIAXIAL TESTS FOR STRENGTH INTERPRETATION II
(FIGS. H-1 THROUGH H-25)
613
APPENDIX H
EXTRAPOLATION OF ISOTROPICALLY-CONSOLIDATED
CYCLIC TRIAXIAL TESTS FOR STRENGTH INTERPRETATION II
As described previously, the isotropically-consolidated
test records were extrapolated to higher strain levels because
of load attenuation and necking problems. These extrapolations
were made conservative and are presented in the following
figures. It should be noted that, although the extrapolations
were intended to account for testing discrepancies, the straight
line extrapolations were rather arbitrary and other extrapolations
equally valid are possible. This strength interpretation is
judged to be conservative because cyclic strain envelopes have
a tendency to level off as cycling continues. A straight line
extrapolation, therefore, can be considered relatively conservative.
615
-20
-15 -
-10
<
t7 -5
<
5 -
)0
/
/
/
TEST NO. 6
/
Kc = 10
/
/
0"3c' = ^'00
psf
/
/
/
N2.5 =22
-
/
Ng =44
N,o =86
~
50 100 150
200
250
NUMBER OF
CYCLES
PREDOMINANT AXIAL CYCLIC
STRESS 2= +
3400 psf
FOR FIRST CYCLES
-20
-15 -
— -\0[-
<
K -5
CO
_l
<
X 0
<
5 -
10
Figure H-1. Cyclic Triaxial Test No. 6
N25= 96 TEST NO. 7
-
N5 = 200 K^ = 1.0 -
N,Q=425 (TjJ = 4100 psf ^^^
—
^^^— -•"'^
^
50 160 150 200 250
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS C!^ + 4 300 psf
FOR FIRST CYCLES
Figure H-2. Cyclic Triaxial Test No. 7
616
-20
-15
-10 -
<
t- -5
CO
X 0
<
5 -
/
TEST NO. 12
Kc = 10
/
°"3c' " '^'^^ P^^
// ^2.5= 9
-
/X Ns =23
^^ N,o =52
1 1
—
V -^£^^20 40 GO-
80 100
—
NUMBER OF
CYCLES
PREDOMINANT AXIAL CYCLIC
STRESS* + 10900 psf
FOR FIRST CYCLES
-20
-15-
- -lOh
<
I- -5
<
X 0
<
5 -
Figure H-3. Cyclic Triaxial Test No. 12
-
N2.5 =
N5 =
N|0
3
■9
= 22
^
^^ TEST NO.
Kc =10
16
-
'l
-|
.. 1 .
^3c = '^'OO psf
1 1
-
5
~
10
15
20
25
NUMBER OF
CYCLES
PREDOMINANT
AXIAL
CYCLIC STRESSES ±
7900
psf
FOR
FIRST
CYCLES
Figure H-4. Cyclic Triaxial Test No. 16
617
-20
-15
-10
N2.5 =415
TEST NO. 4 1
Kc = 10
CTjj.' = 4100 psf
100 150 200
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS ^ + 4700 psf
FOR FIRST CYCLES
-20
-15 -
— -10 -
<
1- -5
CO
5 -
10
Figure H-5. Cyclic Triaxial Test No. ^1
N25= 190 TEST NO. 47
-
N5 = 370 Kc = 1.0 -^^"^
N|Q = 790 0-3^ = 4100 psf ^^^
^^0^ ^
^
^.^^^^"""'^
r 1 1^^ 1 1
100 . 200 300 \^ 400 500
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS ^ ± 2800 psf
FOR FIRST CYCLES
Figure H-6. Cyclic Triaxial Test No. k"]
618
-20
-15
-10 -
<
•- -5
<
X 0
<
5-
10
y
y TEST NO.
72
/
/ K^ =1.0
y^ 0-3^' = 16 400 psf
y
y
/^ ^2.5= 3
y N5 =8
/
y N,o =16
~
* —
~~25
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS :^ +
12000 psf
FOR FIRST CYCLES
-20
-15 -
— -10 -
z
<
t- -5
_J
<
X 0
5 -
10
Figure H-7. Cyclic Triaxial Test No. 72
J, —
-»'
^
N2.5 = 5 ^^^
N5=I2
^0 = 25
'
^^ TEST NO. 73
^^ K^ = 1.0
<<
^^jj_;::lj; 0-3^ =16 400 psf
1 . . 4-- ..;;^i^- ) 1 1
'
—
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS :i: ± 8600 psf
FOR FIRST CYCLES
Figure H-8. Cyclic Triaxial Test No. 73
619
-20
-15 -
-10 -
<
<
X 0
5 -
10
/
/
TEST
NO,
74
/
^ :
1.0
/
/
°-3c
= 16400 psf
/
y
^2.5
^5
= 2
= 4
^
^
1
1
= 9
■"-— .
■ — ^ —
1
-10
1
-I5_
20_
25
NUMBER
OF
CYCLES
PREDOMINANT
AXIAL
CYCLIC
STRESS
~ +
12 900 psf
FOR FIRST CYCLES
Figure H-9. Cyclic Triaxial Test No. lU
-20
-15 -
-10 -
H -5
<
X 0
<
51-
/■■ ■ ■ —
/
/ N2 5=''^
TEST NO. 76
/
/
/
N5 = 25
N,o = 5l
K = 1.0
0-3^ = 16 400 psf
~
/
/
/
/^^^
—
-—
-
1 1
1 1
2'5-
50 75
100 125
NUMBER OF CYCLES
PREDOMINANT
AXIAL CYCLIC
STRESS ^ + 7000 psf
FOR FIRST
CYCLES
Figure H-10. Cyclic Triaxial Test No. 76
620
-20
-15 -
-10 -
-5
10
/
/
-
N2.5=8 /
N5=ll /
-
/ TEST NO. 81
/ Kc = 1.0
-
/ o-jp' = 16 400 psf
5 10 15 20 25
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS :t + 10 600 psf
FOR FIRST CYCLES
Figure H-11. Cyclic Triaxial Test No. 8l
621
-20
N =4
2.5
TEST NO. 33
Kc = 10
cr,. '= 28 7 00 psf
10
10 20 ^irrso.^-- 40 50
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS -; ± 17200 psf
FOR FIRST CYCLES
-20
-15 -
— -10 -
<
q:
I- -5
<
X 0
5 -
Figure H-12. Cyclic Triaxial Test No. 33
y'
y
N25=8 y^ TEST NO. 34
~
N5 =17 ^y K^ = 1.0
N|Q=36 ^y ^^ 0-3^'= 28 700 psf
^ ^^
_
X ^^,,,0''^ —
^
/ ^^^^"^"^
y^ ^^^^^^
y^^,*^*^^
^
1 — ca, :r J^^ ' ' '
10 20 30 40 50
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS ^ ± 13300 psf
FOR FIRST CYCLES
Figure H-13. Cyclic Triaxial Test No. 3^
622
-20
- 15 -
^-lOh
<
tl -5
<
X 0
5 -
N2.5-24
_ N5 =49
""''^ — "^^ 1 1
— ^ —
TEST NO. 35
K^ = 1.0
0-3^ ' = 28 700 psf
1 1
20 4(5" "60 80 160
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS -± 11300 psf
FOR FIRST CYCLES
-20
-15 -
- -10 -
<
cc
\- -5
to
5 -
10
Figure H-1^. Cyclic Triaxial Test No. 35
N2.5=2
/^ TEST NO. 36
N5 =3
N,o--6
/ K,= 1.0
"^ a = 28 700 psf
3c
^
—
/.
. — j — __■«-
.1 1 1 1
2
4 6 8 10
NUMBER OF CYCLES
PREDOMINANT
AXIAL CYCLIC STRESS ^ + 21500 psf
FOR FIRST
CYCLES
Figure H-I5. Cyclic Triaxial Test No. 36
623
- zv
y
— 15
N2.5
- N5
= 4 /^ TEST NO. 37
= 9 1 •'^ K, = 1.0
N,0
= 17 / /-^ ^^3^ = 28700 psf
/ y
-10
-
/ y
~
-5
0
^
/y
1 —^ 1 1 1 1
-
5 10 15 20 25
~~~
NUMBER OF CYCLES
5
-
-
PREDOMINANT AXIAL CYCLIC STRESS :^ +15600 psf
in
FOR
FIRST CYCLES
Figure H-16. Cyclic Triaxial Test No. 37
-20
-15 -
-10 -
<
I- -5
<
X 0
5 -
N5 =3 ^^
TEST NO. 70
K^ = 1.0
N,0 = 6 /^
0- '= 28 700 psf
^
y
1 — ^^-^ 1 1 ! —
-
2 4 - 6 — 8-
1 Q — —
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS
FOR FIRST CYCLES
cc± 23300 psf
Figure H-I7. Cyclic Triaxial Test No. 70
624
- 20
-15 -
-10
z
<
cr
I- -5
_l
<
X 0
5 -
10
TEST NO. 38
-
N„ . = >1000 ^c = '0
o-jj = 53300 psf
-
^„___-..-...:
100 200 300 400 500
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS ~ + 16100 psf
FOR FIRST CYCLES
Figure H-l8. Cyclic Triaxial Test No. 38
-20
-15 -
^ -10-
<
a:
I- -5
<
X 0
5 -
N25= 13 TEST NO. 39
-
N 5 = 25 Kj. = 1.0
N|Q = 50 o-^^' = 533 00 psf
-
5 10 15 20 25
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS ::^ ±28500psf
FOR FIRST CYCLES
Figure H-19. Cyclic Triaxial Test No. 39
625
-20
-15
'2.5
= 6
TEST NO. 42
Kj, = 1.0
0-3^' = 53300 psf
I L
2 3 4
NUMBER OF CYCLES
S
PREDOMINANT AXIAL CYCLIC STRESS :?:+ 37700 psf
FOR FIRST CYCLES
-20
-15 -
-10 -
<
cr
^ -5
5 -
10
Figure H-20. Cyclic Triaxial Test No. 42
^2.5 = 3
^^
-
N5 =6
^^^
N,0='2
y ^^-^
y^ ^^^ TEST NO. 65
X^^^ K, = 1.0
^
1
^^"^ o-jg' = 533 00 psf
^
4 6 8 L°___
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS :t ± 20700 psf
FOR FIRST
CYCLES
Figure H-21 . Cyclic Triaxial Test No. 65
626
-20
-15 -
■10 -
<
I- -5
<
X 0
5 -
10
N2,5 = 5
N5 =12
N.o --26
^^ TEST NO. 66
1 ^-^ K, = 1.0
J^ 0-3^. = 53300 psf
\ 1 1 1
5
^10 i5 2'o 25
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS :^ + 20 700 psf
FOR FIRST
CYCLES
Figure H-22. Cyclic Triaxial Test No. 66
z
<
tr
\-
co
_j
<
-15
-10
-5
0
5
in
^2.5=
- N5 =
N,0 =
3
6
II
1
^ —
/ ^^^ TEST NO. 67
/ ^--^ Kc = 10
/ ^^ o-jj." = 533 00 psf
<
2 4 6 8 10
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS c:t: + 30100 psf
FOR FIRST CYCLES
Figure H-23. Cyclic Triaxial Test No. 67
627
-20
<
•- -5
if)
<
X 0
5 -
N2 5 = 50
TEST NO, 68
Ng =100
Kc = 10
N,o =200
Q- ' = 53300 psf
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS ^+ 15800 psf
FOR FIRST CYCLES
-20
Figure W-lk . Cyclic Triaxial Test No. 68
TEST NO. 69
Kc = 1.0
(TjJ = 533 00 psf
5 -
10
4_ 6 8 ^10
NUMBER OF CYCLES
PREDOMINANT AXIAL CYCLIC STRESS tt + 35400 psf
FOR FIRST CYCLES
Figure H-25. Cyclic Triaxial Test No. 69
628
APPENDIX I
CYCLIC TRIAXIAL TEST RESULTS FOR MODELED OROVILLE
GRAVEL USING STRENGTH INTERPRETATION II
Figures I-l through I-IO are cyclic test results
employing strength interpretation II.
629
-0 'SS3diS 80iVIA3a OHOAD
630
'ss3yis aoiviA3a onoAO
631
z
■% 2
Q- « ^
e S. iiJ
o o o ^ _1
055- s § ^
'^ (0 0 (0 CVJ 00
Q 03 10 C\J OD _■ _
-1 z
UJ - 0
> 0 ,'*'
< 1- ^ b
0 s^tr ^ ^„ _
" .- UJ 0 = ^
^m
7
^. CVJ ^ ^ > <« UJ
-1 2 ^ 1- UJ ir
/
-1 Q UJ - S "^ =>
/
> S°"t - ^
/
0 §UJ2 tl UJ ^
/
O'^pS-J?'^ 3
/-J
-1 < 0 ** i^ ^ 0
/ 4^
-1 _J UJ 1- H 0 UJ
/ 7
i^ UJ Q- — 0 < a:
/ /
5 q: c/) ? 0 CD u.
/ /
7
m
/,
S5
/ 1
•
0
1
'
0
1 j
+1
/•/
< ,
' /
/«
/
^5
/
f
^•B
0
If)
7
/
/
^55s5vO
+1
1
/
</) m 0 0
"
/ i
UJ ■ • •
<
' /
3 CM 10 0
< +1 +1 +1
Q >
55
I
r
2 Q
<\J
^N.
/
_ , , UJ < < < _
+1
^s.
/
^ 1- •" "> -
/
0 < - - -
<
^•^^ /
/
UJ -1 z z z
^^/
/
1 ? < < <
-■ ?: (E (T q:
/
^ •- •- •-
t {/) to «n
k^
<J
1
H
\
s.
X -I _1 _1
^N.
UJ < < <
^^V.
"^ X X X
^
,. /
< < <
/ ^
3 C
1
f
<
r
■^ r-i
ii^ ^
isd "^ 'ss3yis aoiviA3a diioao
632
^sd ''"-D 'SS3yiS yOiVIABQ OnOAO
633
OROVILLE GRAVEL
WELL GRADED 2 tNCH TO NO. 200
RELATIVE DENSITY, D^ = 86 %
SPECIMEN DIAMETER = 30.5 cm
ikiixi A 1 irc err TU/c-
z
z
a. Q. ill
_l
o o o
'f 00 _ _
ro
b
n- ■" . y
CONFINING PRESSU
BACK PRESSURE u
K
FREQUENCY
■ /
j m
q
in
<
■
o
o
<
'/
m
CVJ
<
/
Q
2
AXIAL STRAIN, e^ = 2.5 % ^
AXIAL STRAIN, e^ = 5.0% •
AXIAL STRAIN, c^ = 10.0 % ■
< <-
tk^y^
o
_l
o.
o
dp
^sd ^^ 'SS3aiS d0lVIA3a OHDAD
634
'ss3yis yoiviA3a onoxo
635
z
e ^ S UJ
'^ (O O lo cvj <n o
Q oo lo m 00 _• _
u ^" " -"„
< 1- ,. b
55
OROVILLE
WELL GRADED 2 IN
RELATIVE DENSITY
SPECIMEN DIAMETE
INITIAL EFFECTIVE
CONFINING PRESSU
BACK PRESSURE i
k
>-
o
z
LU
o
UJ
(T
li.
1 •
IK
6
o
m
/ /
in
CO
^'
//
<
^* ■
in o o
Cvi lO o
Q ,1 „ 1.
^
/
e) - ' -
UJ ? ? ?
1 < < <
-■0:0:0:
1- 1- K
w to trt
_J -J _l
< < <
XXX
< < <
^
UJ
_J
o
>
o
dp
isd ^ 'ss3ais aoiviA3a onoxo
636
^sd % 'SSBaiS b01VIA3a diioao
637
z
^
1
OROVILLE GRAVEL
WELL GRADED 2 INCH TO NO. 2
RELATIVE DENSITY, Dr = 86
SPECIMEN DIAMETER = 30.
INITIAL EFFECTIVE
w 9 b
00 CO _
.a u
3 it
UJ
K
3
UJ "
BACK PR
FREQUE
/ ,
■/ ^°
/ °
/ °
1
/ • /
55
o
m
/ i
/ ^
•
4« ■
lO o o
cJ in CJ
Q '
•
1 -^
S J* ^'^ <
O - - -
LJ 12 2
, < <t <
-1 CC q: (E
•- 1- 1-
(O CO CO
_l _l -1
< < <
XXX
< < <
1 ^
^
638
isd "jj 'ss3yis aoiviA3a diioad
OROVILLE GRAVEL
WELL GRADED 2 INCH TO NO. 200
RELATIVE DENSITY, D^ =86%
SPECIMEN DIAMETER = 30.5cm
INITIAL EFFECTIVE
CONFINING PRESSURE 0- ': 53300 psf
BACK PRESSURE ub = 8200 psf
.
S
\
Ul
_l
o
9S ■
CVJ _ /
o /
55
o
6
>- /
<-> /
z /
UJ /
3 /
o /
UJ /
0^ ■
u. T
*\ <J^
/ «
9
IT)
/ /^
<
(1/
D VALUES)
= 2.5 % ▲
= 5.0% •
= 10.0 % ■
M ^ ^
UJ i^ J* ^ <
O < - - -
o < < <
-J OL CC Q. Q.
< H 1- H
(t (rt CO (/5
X _l _l -I
Ul < < <
"" X X X
< < <
^ ^ ^
jsd ''Pjs 'ss3yis yoiviA3a oiioao
639
APPENDIX J
PROCEDURE FOR INTERPRETING CYCLIC TRIAXIAL
TEST DATA TO DETERMINE CYCLIC SHEAR STRESS
ON POTENTIAL FAILURE PLANE
641
APPENDIX J
PROCEDURE FOR INTERPRETING CYCLIC TRIAXIAL TEST
DATA TO DETERMINE CYCLIC SHEAR STRESS ON
POTENTIAL FAILURE PLANE
Current procedures in evaluating the dynamic strength
of an embankment utilize cyclic strength test data to assess
the strain potential of each individual soil element. The
dynamic strength of the soil would be dependent upon the
stress conditions existing on the potential failure plane
prior to seismic loading. The dynamic strength of a soil
element would be determined by the performance of a laboratory
specimen which duplicated the static shear and normal stresses
on the failure plane. A fundamental assximption is that the
horizontal planes within an embankment are the most critical
from a viewpoint of seismic stability. To represent the static
stress conditions on the failure plane in the field, the static
vertical normal stress (^y) and the alpha (OC) value are used.
The alpha value is defined as the ratio of the initial static
shear stress, tT^ , divided by the static normal stress, ^f^r
on the failure plane.
The potential failure planes in a triaxial sample are
assumed to be, dependent upon the consolidation stress ratio
(K ) of the sample. For isotropically-consolidated samples
(K =1.0) the failure planes are assumed to incline 45 from
the horizontal. Failure planes for anisotropically-consolidated
samples are assumed to incline 45 + 0'/2 to the horizontal.
To obtain the current stress conditions required to cause a
specified amount of failure in a particular number of cycles,
6A3
A p, Mohr's circle relationships must be employed. These
relationships are used to determine both the initial static
stresses and the superimposed cyclic stresses on the failure
plane in the sample. The procedures for both isotropically-
consolidated and anisotropically-consolidated triaxial samples
are shown in Figures J-1 and J-2.
As discussed previously in the main text, the cyclic
stresses in the cyclic triaxial test must be modified by the
C correction. This correction is assumed to be unity for
r -^
consolidation stress ratios (K ) of 1.5 or greater. For
isotropically-consolidated triaxial samples, C can range from
0.5 to 1.0 depending upon the field K value. For the
isotropically-consolidated cyclic triaxial tests carried
out for the modeled Oroville gravels, a C value of 0.6 was
used.
A fairly large testing program was carried out for
the modeled Oroville gravel. Because of this, sufficient data
were generated to assess most static stress conditions within
the embankment. The cyclic strength is plotted as the cyclic
shear stress required to cause a particular failure criterion
in a specified number of cycles for a range of consolidation
stresses. The shear strength envelopes for five percent com-
pressive strain in ten cycles is presented for illustration
in Figure J-3.
644
" fc -
A r,
r
0.0
= Cr -^^ —
Figure J-1. Procedure for Interpreting Cyclic Triaxial Test
Data for Isotropical ly-Consol idated (Kj.=1.0)
645
r
o-fc - -^ [(Kj + D-lK^-l) cos(l80-2e)l
Tj^^ — ^ [(K^-l) SIN (180 - 2 9)1
'fic (K^-l) SIN (180-29)
+ I)-(K -I) COS (180- 29
(K -1) + cr.
] SIN
(180-29)
~ dp
ATT,
SIN (180 - 29)
Figure J-2. Procedure for Interpreting Cyclic Triaxial Test
Data for An i sotropical ly-Consol i dated (K^=1.0)
646
— 20000 -
16000 -
a.
'12000
LlI
z
<
_l
a. 8000
UJ
4000
-1 1 1 1 1 r
5% COMPRESSIVE STRAIN IN 10 CYCLES -\
20000 40000 60000
NORMAL STRESS ON FAILURE PLANE
DURING CONSOLIDATION ; cr^^ ( psf )
Figure J-3. Cyclic Strength Envelopes for Five Percent
Compressive Strain in Ten Cycles
647
APPENDIX K
CYCLIC TRI AXIAL TEST RESULTS FOR MODELED OROVILLE
GRAVEL USING STRENGTH INTERPRETATION I
Figures K-1 through K-10 are cyclic test results
employing strength interpretation I.
649
*ss3dis aoiviA3a diidao
650
'SS3H1S dOiVIA3a DllDAO
651
z
^ 2
200
6%
0.5 cm
8700p
200 ps
0
CYCLE
_]
Q oo ro cvi 00 ^ —
Z " "
UJ
^
? . • 'b-
®
^
1
LLE GR
I '^ a: lij' XI o
w « 5 i=2 uT
1
_
UJ Q Q UJO- 5<
/ n^
>
,L GRAD
ATIVE
CIMEN
lAL EFF
FINING
K PRES:
QUENCY
11 /p '
o
\\\
o
jna
-J _) UJ |_Z o u
III
y lu Q. 50 < a:
Li I
5 a: <rt ?o
m u.
mil
55
m
0 1
ji 1 j
6 /
1 w 11
S5
X®
^ M /
'Ik
55
"" 11 / /
1 r
in 0
"^ < / /
1 1
N d
+1 " A/
/ □ / /
+1 +1 ^
/ / /
II 11 0
"< ® / /
/ /
< < H vO
/ /
w « 0 0--
^^^ / ^ /
/'T^
S S if ^ 9
1 / 1 1
if
cvj in 1--' 0 0 0 H +1 "<
k/ ►/ /
a
z -H -H +1 ^ +1 ^ _, " -
/ / h
jo
g " " " (T ■• tr <t w
/ 1
1 j
Q
1- < < <x <x •-
/ / J
/
— 2
UJ
1 1 u> <i> !•> !?: u r\ — V
lii 2:" z z z z z \^
\/ 7 Ji
UJ
3 < < < < < < \^
>^ / //
_l
IITIAL LIQ
XIAL STR
XIAL STR
XIAL STR
XIAL STR
XIAL STR
XIAL STR
A^
^^\ ■xLO
± < < < <
< <
^^
isd '^Pd
'ss3dis aoiviA3a onoAo
652
z
« s
o " o Z^ -"
O >5 in O O o
JD O ro CJ o <->
Q 00 ro lo oo _■ _
—1 Z 1
UJ
> o "
< 1- ^ b"^
en a - ~"
C) I q: lu £, u
^ o - UJ a: -, v-
z ?: H Ui3
UJ t UJ > w
I CM CO 2 - <n UJ
— ' z $ •" UJ (r
-1 Q iL ^ <->ir 3
s?
— ujQQUJa.OT ^
> Q H- (/5 ?:
O < UJ z ,"*- « UJ "
o
-1 < o 2 u. ^ o
^5 °« +1
/I
z
o
-J _l UJ 1- Z O UJ
O |C "
/ 1
1-
UJ UI Q. — o < o:
5 o: en ? o CD u.
•ft -H < 1
+1 li " /
1;
<
u.
" < /
IL
UJ
'""i^y
/ff--
'
/ - ■"
®
^^^^vT* /
7 i :.
S5
/K "
o
o
//^ '
"
/^/ J
b'^v
<
s />/y /
/o
o<]n[>x '
,
/ ^/
/o
o
<•
/ r / n
>P vO vO ^ UJ
^
/ /
m O m o <
> / t/ //
cJ m r~ O o
+1 +1 +m ^
., 1. .1 u oc
®/
/ /□ /©
t-
/
< ,< < < UI
Hi V it) V ^
/
□/ (zy
Xt> c
2 Z Z Z Z /
/
< < < < <
/
z (T tc K (r a:
/
/^ J'*'
i-v »— r~ r— »~ r
^ CO OT «0 to (n
/
//
1-
/
/ /
i 'i<<i<i /
/□
/ /
/ /
Ld UJ X X X X X
/ /
(0 3 < < < < <
<!
yQi
UJ o
r j^
Ij 3 -J -J -" -" -J
/
y
/ .
/
_l 3 3 3 U 3
y< /
<]
< o o o o c
4^
H <o <n CO CO (?
— UJ UJ UJ UJ UI
E Q: (T (T (£ (T
1
o —
(T
t)
UJ
CJC
CQ
4-1
>
(O
3
<u
9 z
1-
|sd ''Pj) 'SS9yiS dOiVIA3a onoAD
653
z
?
« s
J
a 1; ^
L.
E „ Q. liJ
1 ^
O o O _I
1
O vOtfl O
o o
o >-
1
U> O 00
CvJ IT) O
1
Q 00 lO CJ CO _• _
— ' H •
1
Ul
1-
1 ° ^ ^"
1
/
CC ^ Q
1
^rj I (E UJ XJ O
1 1
" - UJ K 3 ^
1 1
Z > t- IU3
llJ ^, - ^ > ^ . .
/ 1
1 «^ (n s ;r *" "^
H z < •- liJ a:
-) Q UJ _ O (T 3
/ 1
/ 1
— ujQQLLiQ.cn
/ 1
> a \>- to >:
/ /
O <ujz^»iu S^
/ /
_ (T o: > uj '^z
a^ iTi
/ /
-• < G ^^ u-
/ / 1
-1 _l LlJ l_ Z O U
III
l^ UJ Q. - O < (t
III
5 (E CO ? O
m u.
/
1
^
/ /
1
► ® 9
/ /
L / /
o
/ /
/ //
,• • If) <
/ /
1
1^ O Z- "
■■ " ^ n
/ / /
1
q: a: o
^/ ^ /
/ /
< < ^ 1^ \
/ /
u, ■" < \
/ 11
/ /
" " x.
/ [> / /
o
0<]Dt>g-
•<• Q ^
Ir^
£ ^
v/ / / y
1
- 1- „ H J* L
/ / 1 1
j
^^S5<S5< \ /
/□ EK /
'
<f o m o o o \/
^/ V / /
cvj in t^' ^ o ^ 'v /\^
/ / //
" 1- t- /\
y/ /© //
< 35 1
(E c (EX ax / \
/ / / 0
"? K
< < <iu <ijJ \ y
yxl / /
CJ CJ
<J
' ' ' * /\
/ / /
" U-
Z Z Z z 2 2 /^ \
r^r / /\.
(EUJ
<<<<<<
V lo / / ^t
<=>
z (E cr a (E q: (E
y^ / -Xi/
w O
O t- t- t- H H H
/ / ^»
\ -
— </i en CO CO en (0
/ /
p-
\
*r — _I -■■
Q "_l_l_l_l_i_j
2 2<<5<<<
/ ^l/
^ <
/ ^\
)-
UJ UJXXXXXx
y Qy \,^
o ^<<<<<<
/ ^v
z
UJ o
y/ N.
1 - _i _i _i _j _i _i
<il ^\
V3 ^y
_| 3 D 3 3 13 3
/
V
< O O O O O O
/
\^
P CO CO CO to cn CO
^^
— UJ UJ LlI llJ U LU
^\
± IE (E (E (£ (E (T
654
dp
isd X 'SSBdiS aOiVIABQ OIIOAD
'SSBdlS yOlVIABQ OnOAO
655
656
'ss3ais yoiviA3a oiidad
-a-
II
^sd '^Pj) 'SS3yiS HOiVIABQ DllDAD
657
(0
o
CO
o
OD
to
cvj
_l
?•
11
11
II
UJ
>
o
t
<
1-
,
^^'
tr
n
(')
—
UJ
•■
bJ
(T
'^
1-
UJ 3
LU
(NJ
(rt
UJ
> W
- W
;'
1- UJ
1
O
O (E
III
Q
UJQ.
->
n
o
<
111
z
U. o
UJ z
cr
tr
>
UJ
o
_i
1-
<
( )
_1 z
_i
UJ
1- z
UJ
a.
5°
:*
ec
If)
G<]DOX
o^ tf^ o^ o~
m O m o
cvj ID :^ O
q: q: q: q:
< <r < <
— CO to to W5
< < < <
3 < <<
O
< Q Q
p to to
— UJ UJ
± o: q:
to CO
UJ UJ
658
dp
isd _D 'ss3ais yoiviA3a onoAO
.(O dp
SS3aiS aOlVIABQ DIIOAO
659
APPENDIX L
CYCLIC TRI AXIAL TEST REPORT - TO BE AVAILABLE EARLY 1979
Appendix L is the cyclic triaxial testing report
concerning tests made for modeled Oroville Gravel samples.
It will be made available in 1979 and will be supplied on
request.
661
APPENDIX M
EMBANKMENT STRAIN POTENTIALS
CFIGS. M-1 THROUGH M-4)
663
APPENDIX M
EMBANKMENT STRAIN POTENTIALS
Figures M-1 and M-2 show the computed compressive
strain potentials in the upstream shell for the "best judgment
case" and the "conservative case". Figures M-3 and M-^ show
two other cases which will not be considered further because
they are within the range defined by Figures M-1 and M— 2.
A rigorous or well— tested procedure has not been
developed for relating actual displacements of an embankment
to computed strain potentials. However, two rough correlations
between strain of laboratory test samples and embankment
deformations have been made — Otter Brook Dam for static
loading, and Upper San Fernando Dam for earthquake shaking.
In both cases, surface deformations of several feet were foiuid
for locations corresponding to axial strain of test samples
greater than 10 percent. These deformations were considered
"excessive" .
On the basis of these correlations, the zones within
the 10 percent compressive strain potential contours in Figures
M-1 and M-2 could be expected to develop excessive deformations.
This would be the three small zones for the "conservative case"
and no zones for the "best judgment case".
The method used to calculate displacement of the Upper
San Fernando Dam can be used as a rough indicator of the magnitude
of displacements. The method is carried out by estimating
deformation in critical zones of high strain potential. This
665
PSEUDO THREE DIMENSIONAL ANALYSIS
PSEUDO K2MAX =^50
PSEUDO CORE Gmax/Su
SHELL K2MAX
CORE G^^^/S
1750
CASE a; PREDICTED FOR BEST JUDGMENT CASE
Figure M-l.i Predicted for Best Judgement Case
ESTIMATED UPSLOPE LIMIT OF SLUMPING
V
TWO DIMENSIONAL ANALYSIS
SHELL K2MAX = 205
CORE Gmax /Su = 1120
CASE b: POSSIBLE EXTREME FOR CONSERVATIVE CASE
Figure M-2. Possible Extreme for Conservative Case.
NOTES =
REANALYSIS EARTHQUAKE
COMPUTER PROGRAM LUSH
CYCLIC STRENGTH INTERPRETATION H - EXTRAPOLATED CYCLIC
TRIAXIAL TEST RESULTS
UNDRAINED CONDITIONS
666
TWO DIMENSIONAL ANALYSIS - COM PUTE R PROGRAM LUSH
REANALYSIS EARTHQUAKE
SHELL K
2MAX
CORE Gmav /S„ =
205
120
CYCLIC STRENGTH INTERPRETATION I
UNDRAINED CONDITIONS
CASE c
Figure M-3. First Strength Interpretation
TWO DIMENSIONAL AN A LYSIS - COMPUTER PROGRAM QUAD 4
REANALYSIS EARTHQUAKE
SHELL K2MAX = 130
CORE Gmax /S, = 2200
CYCLIC STRENGTH INTERPRETATION H
UNDRAINED CONDITIONS
CASE d
Figure H-k. Second Strength Interpretation
667
procedure requires conversion of compression strain potential
to shear strain potential. For saturated soils defonning at
constant voliJine in plane strain conditions, the shear strain
potential can be taken as 1.5 times the compressive strain
potential. Since the elements developing lower strain potentials
will tend to restrain the movement of elements of higher strain
potentials, an appropriate estimate of the deformation in a zone
would employ an average value of shear strain potential. By
taking this average shear strain potential and multiplying it
by the height of the critical zone, one obtains the relative
horizontal displacement between the top and bottom of the zone.
For the "best judgment case", distribution of compressive
strain potentials has not been defined except that they are less
than > percent essentially throughout the upstrecim shell. For
illustration purposes, an average of 2 percent is assumed for
compressive strain potential over a height of 91 metres (300 ft.).
Horizontal displacement would then be calculated as 0.02 x 1.5 x
91 = 2.7 metres (9 ft.).
For the "conservative case", the average compressive
strain potential within the 5 percent contours is about 8 percent,
and the average height within this contour is 91 metres (300 ft.).
Relative horizontal displacement between the surface of the slope
and bottom of this contour would be calculated as .08 x 1.5 x 91 =
11 metres (36 ft.). Because this method is only a rough indicator,
the displacement can best be described as a few tens of feet, or
in round numbers, 10 metres.
668
Overall behavior associated with the illustrated
strain potentials might reasonably be as follows:
— upstream displacement of the slope by a few
tens of feet in the interval between the two
berms .
— slumping of the shell material near the upper
berm.
— bulging of the shell material near the lower
berm.
Displacement and slumping would be limited to the
upstream shell material as indicated by the strain potential
pattern. Slumping would not be expected to extend upslope
beyond the k^ degree line shown in Figure M— 2 (judgment based
on extent of slumping at Lower San Fernando Dam). The compacted
gravel in the upstream shell would be as strong and perform as
well after deformation as before.
669
6—950 2-79 IM
THIS BOOK IS DUE ON THE LAST DATE
THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW
BOOKS REQUESTED BY ANOTHER BORROWER
ARE SUBJECT TO IMMEDIATE RECALL
AUG '^^ 2008:
!'■• IL 2008
Physical Sci«nce$Utt^
\t, 8 "»*
LIBRARY, UNIVERSITY OF CALIFORNIA, DAVIS
D4613-1 (5/02)M
3 1175 00565 5892
Live Music Archive
Librivox Free Audio
Metropolitan Museum
Cleveland Museum of Art
Internet Arcade
Console Living Room
Books to Borrow
Open Library
TV News
Understanding 9/11