GUIDELINES FOR EVALUATING AND MITIGATING SEISMIC HAZARDS IN - PDF document

SPECIAL PUBLICATION 117 GUIDELINES FOR EVALUATING AND MITIGATING SEISMIC HAZARDS IN CALIFORNIA Adopted March 13, 1997 by the State Mining and Geology Board in Accordance with the Seismic Hazards Mapping Act of 1990 Copies of these Guidelines, California’s Seismic Hazards Mapping Act, and other related information are available on the World Wide Web at Copies also are available for purchase from the Public Information Offices of the California Geological Survey. CALIFORNIA GEOLOGICAL SURVEY’S PUBLIC INFORMATION OFFICES: Southern California Regional Office Publications and Information Office Bay Area Regional Office 655 South Hope Street, Suite 700 801 K Street, MS 14-33 185 Berry Street, Suite 210 Los Angeles, CA 90017-3231 Sacramento, CA 95814-3532 San Francisco, CA 94107-1728 (213) 239-0878 (916) 445-5716 (415) 904-7707

Contents ACKNOWLEDGMENTS ............................................................................................................................................ 4 CHAPTER 1 - INTRODUCTION ............................................................................................................................ 6 Objectives .................................................................................................................................................................... 6 CHAPTER 2 - DEFINITIONS, CAVEATS, AND GENERAL CONSIDERATIONS ......................................... 7 Definitions ................................................................................................................................................................... 7 Caveats.......................................................................................................................................................................... 8 Relationship of these Guidelines to Local General Plans and Permitting Ordinances ............................................... 11 Relationship of these Guidelines to the CEQA Process and Other Site Investigation Requirements ........................ 11 Criteria for Project Approval ..................................................................................................................................... 12 Engineers or Geologists - Who Does What? .............................................................................................................. 13 CHAPTER 3 - OVERVIEW OF INVESTIGATIONS FOR ASSESSING SEISMIC HAZARDS ................... 14 Introduction ................................................................................................................................................................ 14 Items to Consider in the Site Investigation Study ...................................................................................................... 14 Screening Investigation .............................................................................................................................................. 15 Quantitative Evaluation of Hazard Potential .............................................................................................................. 16 Content of Reports ..................................................................................................................................................... 16 CHAPTER 4 - ESTIMATION OF EARTHQUAKE GROUND-MOTION PARAMETERS .......................... 18 Introduction ................................................................................................................................................................ 18 Simple Prescribed Parameter Values (SPPV) ............................................................................................................ 19 Probabilistic Seismic Hazard Analysis (PSHA) ......................................................................................................... 20 Deterministic Seismic Hazard Analysis (DSHA) ...................................................................................................... 20 Selection of a Site-Specific Design Strong-Motion Record ....................................................................................... 21 CHAPTER 5 - ANALYSIS AND MITIGATION OF EARTHQUAKE-INDUCED LANDSLIDE HAZARDS ............. 23 Screening Investigations for Earthquake-Induced Landslide Potential ...................................................................... 23 Quantitative Evaluation of Earthquake-Induced Landslide Potential ........................................................................ 25 Evaluation of Potential Earthquake-Induced Landslide Hazards ............................................................................... 36 Mitigation of Earthquake-Induced Landslide Hazards .............................................................................................. 37 CHAPTER 6 - ANALYSIS AND MITIGATION OF LIQUEFACTION HAZARDS ...................................... 40 Screening Investigations for Liquefaction Potential .................................................................................................. 40 Quantitative Evaluation of Liquefaction Resistance .................................................................................................. 42 Evaluation of Potential Liquefaction Hazards ........................................................................................................... 45 Mitigation of Liquefaction Hazards ........................................................................................................................... 48 CHAPTER 7 - GUIDELINES FOR REVIEWING SITE-INVESTIGATION REPORTS................................ 52 The Reviewer ............................................................................................................................................................. 52 Reviewing Reports ..................................................................................................................................................... 53 REFERENCES CITED ........................................................................................................................................... 58 RELATED REFERENCES .................................................................................................................................... 64 APPENDIX A SEISMIC HAZARDS MAPPING ACT ....................................................................................... 69 2

APPENDIX B SEISMIC HAZARDS MAPPING REGULATIONS................................................................... 74 APPENDIX C TECHNICAL TERMS AND DEFINITIONS.............................................................................. 78 APPENDIX D SOURCES OF STRONG-MOTION RECORDS ........................................................................ 79 APPENDIX E GEOLOGIC ENVIRONMENTS LIKELY TO PRODUCE EARTHQUAKE-INDUCED LANDSLIDES........................................................................................................................................................... 80 ILLUSTRATIONS Figure 1. Approximate range of pseudo-static seismic coefficient "k" for anticipated factor of safety as proposed in the literature ..................................................................................................................................................................... 33 Table 1. Definition of "Project" ................................................................................................................................... 9 Table 2. Recommended content for site-investigation reports within zones of required investigation ...................... 16 Table 3. Relative abundance of earthquake-induced landslides from 40 historical earthquakes ............................... 22 Table 4. Comparative advantages of SPT and CPT methods ..................................................................................... 44 3