An Explanatory Text to Accompany the 1:750,000 Scale Fault and Geologic Maps of California

Physical! Sci .Lib. TN 24 C3 A3 NO. 201 PHYSICAL S«K AN EXPLANATORY TEXT SI TO ACCOMPANY THE 1:750,000 SCALE FAULT AND GEOLOGIC MAPS OF CALIFORNIA PURPOSE AND USE EVOLUTION OF FAULT AND GEOLOGIC MAPS FAULTS AND EARTHQUAKES MAJOR STRUCTURAL BLOCKS OF CALIFORNIA FAULT PATTERNS VOLCANOES THERMAL SPRINGS AND WELLS INDEXES TO: Faults Hot Springs Formations Source Data 1 s^l -J BULLETIN 201 AN EXPLANATORY TEXT TO ACCOMPANY THE 1:750,000 SCALE FAULT AND GEOLOGIC MAPS OF CALIFORNIA By Charles W. Jennings Geologist 1985 L^ CALIFORNIA DEPARTMENT OF CONSERVATION ^^'"'M^ DIVISION OF MINES AND GEOLOGY 1416 NINTH STREET, ROOM 1341 SACRAMENTO, CA 95814 CONTENTS Page Preface vii Abstract ix Introduction 1 Purpose and uses 1 Value of map compilations 2 Base Mop 2 Source data 2 Acknowledgments 3 Part I Fault Map of California Introduction 7 Recognition of faulting as cause of eartliquakes 7 Evolution of fault maps of California 7 First fault map of the state— 1908 7 Second fault map of California— 1922 - 9 Faults sfiown on Geologic Map of California— 1938 10 Combined Wood and Jenkins fault map of tfie southern half of the state— 1947 11 Earthquake Epicenter and Fault Map of California— 1964 12 Earthquake Epicenter Mop of California— 1978 12 Small-scale fault maps of California 12 Preliminary Fault and Geologic Map of California— 1973 14 Fault Map of California— 1975 edition 14 Depiction of faults 15 Fault classification 15 Fault definitions 15 Historic faults, earthquakes, and creep 16 Earthquakes with surface rupture 16 Recorded fault creep 18 Displaced survey lines 23 Seismicity 23 Quaternary faults 24 Identification 24 Problems 24 Plio-Pleistocene boundary controversy 26 Major Quaternary faults 26 Philosophy of conservatism 26 Pre-Quoternory faults 27 Accuracy of fault locations 27 Offshore structure 28 Coast Range thrust 28 Circular fault structures 28 Future changes in fault depiction 29 Fault patterns 30 Structural provinces 30 Predominant fault trends defining structural provinces 31 Major structural blocks with predominantly northwest faults 31 Coast Ranges block 31 Peninsular Ranges block 31 Major structural block having predominantly east-trending faults 31 Transverse Ranges block 31 Santa Ynez and Son Gabriel sub-blocks 31 Banning sub-block 31 San Bernardino sub-block 31 Pinto Mountains sub-block 31 Major structural blocks charocterized by northeast-trending fault boundaries 32 Mojove block 32 Tehachapi block 32 iii Page Major structural blockj charocterized by north-trending faults 32 Kern Canyon block 32 Ponomint and Death Valley blocks 32 Worner block 33 East Sierra block 33 Cascade block 33 Gordo block 33 Major structural blocks characterized by other types of faults 33 Sonoran Desert block 33 Sierra Nevada block 33 Klamath block 33 Modoc block 33 Coast Ranges sub-blocks 33 Santo Lucia and Gobilan sub-blocks 33 Son Francisco ond Berkeley sub-blocks 34 Diablo and Great Valley sub-blocks 34 Stonyford sub-block 34 Peninsular Ranges sub-blocks 34 San Clemente and Cotalina sub-blocks 34 Polos Verdes and Inglewood-Son Diego sub-blocks 34 Santa Ana, Riverside, and Son Jacinto sub-blocks 34 Sub-blocks within the Modoc block 34 Summary 34 Fault couples 35 En echelon faults 35 Regularity of fault spacing 35 Summary on fault geometry 39 Faulting and patterns of seismicity 39 Relationship of epicenters to faults 39 Relationship of surface rupture to earthquake magnitude 41 Faults with recurring earthquake activity 41 Patterns of seismicity 42 Cautions in use of Fault Map of California for land-use planning 42 Depiction of volcanoes 43 Distribution and age 43 Relation of volcanoes to faults 44 Volcanic hazards 44 Depiction of thermal springs and wells 45 Temperoture 45 Mode of occurrence of hot springs 45 Distribution of hot springs 45 Part II Geologic Map of California Introduction 51 History of geologic mops of California 51 The first attempts 51 Preliminary Minerological and Geological Map of the State of California— 1891 51 Geological Mop of the State of Colifornia— 1916 51 Geological Mop of California— 1938 52 Geologic Atlos of California— 1958-1969 52 Two smoll-scole geologic maps of California (1966 and 1968) 54 Geologic Map of California— 1977 54 History of the project 54 Uses of the geologic map 55 Objectives and contents 56 Representation of faults 56 Representation of contacts 56 Compilation method 56 Classification of rock units and special problems 58 Colors, patterns, symbols of rock units, ond mop appearance 61 Geologic time scale 66 Volcanoes 66 Botholiths ond plutons 66 Offshore geology 68 References cited in Parts I ond II 69 iv Part III Appendices Page APPENDIX A: INDEX TO FAULT NAMES SHOWN ON THE FAULT MAP OF CALIFORNIA, 1975 EDITION Named faults shown 77 Procedure for naming faults 77 Index to fault names 78 Supplemental index to fault names 80 APPENDIX B: TABULATED LIST OF THERMAL SPRINGS AND WELLS Data used and acknowledgments 81 Locating thermal springs and wells 81 Tabulated list of thermal springs and wells 81 References cited in Appendix B 1 17 APPENDIX C: INDEX TO THE GEOLOGIC FORMATIONS GROUPED WITHIN EACH UNIT PORTRAYED ON THE GEOLOGIC MAP OF CALIFORNIA, 1977 EDITION Explanation 1 19 Index 120 APPENDIX D: SOURCE DATA INDEX How to use this index 125 Other references 125 Indexes to published geologic maps 125 Indexes to theses 125 Explanation of maps 127 Bibliography (by atlas sheet) 128 LIST OF ILLUSTRATIONS Figures Figure 1. Increase of published geologic map data for California 2 Figure 2. Theses on California geology 1892-1976 (exclusive of topical and brood regional studies) 3 Figure 3. Bruce Clark's 1930 map of California showing "principal known primary faults" 13 Figure 4. Mop of California and adjacent terrone showing major Quaternary faults and identifying historic fault breaks, occurrences of fault creep, and triggered creep 19 Figure 5. Mop showing small-magnitude earthquake epicenters reported during 1975 25 Figure 6. Generalized mop of the Long Volley-Mono Craters area showing location of faults 29 Figure 7. Numerous short NW and NE conjugate faults characteristic of the Panomint and Death Valley blocks 32 Figure 8. Diagonal faults formed between two major strike-slip faults, the Son Andreas and the Rodgers Creek-Heoldsburg faults ... 36 Figure 9. Diagonal faults formed between the strike-slip Son Andreas and Son Gabriel faults 37 Figure 10. Diagonal folds formed between the San Andreas and Rinconada faults in thin sedimentary cover overlying granitic basement rocks 38 Figure 11. Fracture zones illustrated by Menard (1955) 40 Figure 12. Part of a tectonic mop of the world (Condie, 1976) including the same area illustrated by Menard 40 Figure 13. Alignment of Tertiary volcanic plugs near San Luis Obispo along a line of weakness presumed to be on ancient fault 44 Figure 14. Relief Mop of California showing geomorphic provinces 48 Figure 15. Geologic Legend (generalized description of rock types) 62-63 Figure 16. State index map showing the boundaries of the individual Geologic Atlas sheets and the source data index mops in Appendix D 126 Page Tables Table 1. Summory of published foull mops of Colifornia 14 Table 2. Comporison of various commonly used fault definitions 17 Table 3. Evidence used for determining fault history 17 Table 4. Port A. Historic surface faulting associated v/ith earthquakes in California 20 Port B. Historic surface faulting associated with earthquakes in Nevado ond Bajo California 22 Port C. California faults displaying fault-creep slippage not associated with earthquakes 22 Part D. Triggered creep along faults associated with earthquakes in California 23 Table 5. California seismic record for 75 years 41 Table 6. Observed volcanic events in California 44 Table 7. Springs neor boiling point temperature 46 Table 8. State geologic mops of California 52 Table 9. Geologic otlos of California (1 -.250,000 scale) 53 Table 10. Derived legend for 1:750,000 scale Geologic Mop of California 59-60 Table 11. Comparison of "American" and "International" mop colors for sedimentary rocks 64 Table 12. Comparison of "American" and "International" map colors for plutonic and volcanic rocks 64 Table 13. Patterns used on Geologic Mop of Colifornio 65 Table 14. Geologic time scale 67 Table 15. Botholifh, plutons, and stocks identified on the 1977 Geologic Mop of California 68 Plates (in pocket) Plate lA. Faults shown on the first fault mop of California. From Mop No. 1 of the State Earthquake Investigation Commission report on the California earthquake of April 18,1906 (Lowson and others, 1908) . Fault names shown in quotation marks ore from the text of 1908 report; other fault names were added from current usage. Plate 1 B. H. O. Wood's abridged version of Lawson's 1908 fault map of California, showing faults and "lines" tentative!/ considered by Wood to be generatrices of earthquakes. Plate IC. Faults shown on the Fault Map of California compiled by B. Willis ond H. O. Wood and published by the Seismologlcal Society of America in 1922 at o scale of 1:506,880. Plate ID. Faults shown on the Geologic Mop of California published in 1938 at 1:500,000 scole. This reduced version, showing faults only, includes all those faults shown on the larger scale mop. Faults were not shown by name on the original mop, but have been identified on this plate. Plate IE. Foult mop of southern California (here slightly generalized) compiled by H. O. Wood. Faults were taken largely from the 1922 Fault Mop of Californio and the 1938 Geologic Mop of California. Plate 2A. Structural provinces of California determined by the prominent fault patterns and characteristics of the faults they contain or bound. Plate 2B. Parallelism between major Quaternary faults and regularity of fault spacing. Plate 2C.

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