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Special Publication 117 SPECIAL PUBLICATION 117 GUIDELINES FOR EVALUATING AND MITIGATING SEISMIC HAZARDS IN CALIFORNIA 2008 THE RESOURCES AGENCY STATE OF CALIFORNIA DEPARTMENT OF CONSERVATION MIKE CHRISMAN ARNOLD SCHWARZENEGGER BRIDGETT LUTHER SECRETARY FOR RESOURCES GOVERNOR DIRECTOR CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, PH.D, STATE GEOLOGIST Copyright 2008 by the California Department of Conservation, California Geological Survey. All rights reserved. No part of this publication may be reproduced without written consent of the California Geological Survey. “The Department of Conservation makes no warranties as to the suitability of this product for any particular purpose.” Cover photograph is of a storm-induced landslide in Laguna Beach, California. Earthquakes can also trigger landslides. 2 SPECIAL PUBLICATION 117 GUIDELINES FOR EVALUATING AND MITIGATING SEISMIC HAZARDS IN CALIFORNIA Originally adopted March 13, 1997 by the State Mining and Geology Board in Accordance with the Seismic Hazards Mapping Act of 1990. Revised and Re-adopted September 11, 2008 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: http://www.conservation.ca.gov/cgs/shzp/Pages/Index.aspx 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 888 S. Figueroa Street, Suite #475 801 K Street, MS 14-33 Earth Science Information Center / Map Sales Los Angeles, CA 90017 Sacramento, CA 95814-3532 Building 3, Room 3-121 (213) 239-0878 (916) 445-5716 345 Middlefield Road, MS 520 Menlo Park, CA 94025 (650) 688-6327 3 CONTENTS CHAPTER 1 ................................................................................................................................... 9 INTRODUCTION .......................................................................................................................... 9 Objectives ................................................................................................................................. 10 CHAPTER 2 ................................................................................................................................. 11 DEFINITIONS, CAVEATS, AND GENERAL CONSIDERATIONS ....................................... 11 Definitions................................................................................................................................. 11 Minimum Statewide Safety Standard ....................................................................................... 12 Areal Extent of Hazard ............................................................................................................. 12 Off-Site Origin of Hazard ......................................................................................................... 14 Relationship of these Guidelines to Local General Plans and Permitting Ordinances............. 14 Relationship of these Guidelines to the CEQA Process and Other Site Investigation Requirements ............................................................................................................................ 14 Criteria for Project Approval .................................................................................................... 15 Engineers or Geologists - Who Does What? ............................................................................ 16 CHAPTER 3 ................................................................................................................................. 17 OVERVIEW OF INVESTIGATIONS FOR ASSESSING SEISMIC HAZARDS ..................... 17 Introduction............................................................................................................................... 17 Items to Consider in the Site Investigation Study..................................................................... 17 Screening Investigation............................................................................................................. 18 Quantitative Evaluation of Hazard Potential ............................................................................ 19 Detailed Field Investigations – General Information Needs................................................. 19 Content of Reports .................................................................................................................... 19 CHAPTER 4 ................................................................................................................................. 22 ESTIMATION OF EARTHQUAKE GROUND-MOTION PARAMETERS............................. 22 Introduction............................................................................................................................... 22 Simple Prescribed Parameter Values (SPPV)........................................................................... 22 Probabilistic Seismic Hazard Analysis (PSHA) ....................................................................... 23 Deterministic Seismic Hazard Analysis (DSHA)..................................................................... 23 Selection of a Site-Specific Design Strong-Motion Record ..................................................... 24 CHAPTER 5 ................................................................................................................................. 26 ANALYSIS OF EARTHQUAKE-INDUCED LANDSLIDE HAZARDS.................................. 26 Screening Investigations for Earthquake-Induced Landslide Potential.................................... 26 Additional Considerations ........................................................................................................ 28 Quantitative Evaluation of Earthquake-Induced Landslide Potential....................................... 28 Detailed Field Investigation.................................................................................................. 29 Geotechnical Laboratory Testing.......................................................................................... 32 Slope Stability Analysis........................................................................................................ 34 Evaluation of Potential Earthquake-Induced Landslide Hazards ............................................. 40 Pseudo-Static Analysis.......................................................................................................... 40 Newmark Displacement Analysis......................................................................................... 40 CHAPTER 6 ................................................................................................................................. 42 ANALYSIS OF LIQUEFACTION HAZARDS .......................................................................... 42 4 Screening Investigations for Liquefaction Potential................................................................. 42 Quantitative Evaluation of Liquefaction Resistance................................................................. 45 Detailed Field Investigation.................................................................................................. 45 Geotechnical Laboratory Testing.......................................................................................... 47 Evaluation of Potential Liquefaction Hazards .......................................................................... 47 Lateral Spreading and Site Displacement Hazards............................................................... 48 Localized Liquefaction Hazards ........................................................................................... 49 CHAPTER 7 ................................................................................................................................. 51 GUIDELINES FOR MITIGATING SEISMIC HAZARDS ........................................................ 51 Introduction............................................................................................................................... 51 Basic Considerations................................................................................................................. 52 Mitigation of Landslide Hazards .............................................................................................. 53 Rotational Landslides............................................................................................................ 53 Fill Displacements ................................................................................................................ 55 Soil Flows ............................................................................................................................. 57 Rock Falls & Topples ........................................................................................................... 58 Mitigation of Liquefaction Hazards.......................................................................................... 60 Large-Scale Displacements................................................................................................... 60 Localized Failures................................................................................................................. 61 Concluding Remarks................................................................................................................
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