SPECIAL PUBLICATION 42 Revised 2018 EARTHQUAKE FAULT ZONES A GUIDE FOR GOVERNMENT AGENCIES, PROPERTY OWNERS / DEVELOPERS, AND GEOSCIENCE PRACTITIONERS FOR ASSESSING FAULT RUPTURE HAZARDS IN CALIFORNIA DEPARTMENT OF CONSERVATION CALIFORNIA GEOLOGICAL SURVEY STATE OF CALIFORNIA EDMUND G. BROWN, JR. GOVERNOR THE NATURAL RESOURCES AGENCY DEPARTMENT OF CONSERVATION JOHN LAIRD DAVID BUNN SECRETARY FOR RESOURCES DIRECTOR CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, PH.D. STATE GEOLOGIST CALIFORNIA GEOLOGICAL SURVEY JOHN G. PARRISH, PH.D. STATE GEOLOGIST Copyright © 2018 by the California Department of Conservation. All rights reserved. No part of this publication may be reproduced without written consent of the Department of Conservation. The Department of Conservation makes no warrantees as to the suitability of this product for any particular purpose. II SPECIAL PUBLICATION 42 EARTHQUAKE FAULT ZONES A GUIDE FOR GOVERNMENT AGENCIES, PROPERTY OWNERS / DEVELOPERS, AND GEOSCIENCE PRACTITIONERS FOR ASSESSING FAULT RUPTURE HAZARDS IN CALIFORNIA Revised 2018 California Department of Conservation California Geological Survey 801 K Street, MS 12-31 Sacramento, CA 95814 Photo: Cottage destroyed by surface fault rupture on the Kekerengu Fault during the Mw 7.8 2016 Kaikoura earthquake, New Zealand. Approximately 10 meters of right-lateral fault displacement occurred under this house, tearing it from its foundation. Photo credit: VML 190573, Julian Thomson, GNS Science / Earthquake Commission III PREFACE The purpose of the Alquist-Priolo Earthquake Fault Zoning Act is to regulate development near active faults so as to mitigate the hazard of surface fault rupture. The stated intent of the Act is to “…provide policies and criteria to assist cities, counties, and state agencies in the exercise of their responsibility to prohibit the location of developments and structures for human occupancy across the trace of active faults.” The Act also requires the State Geologist to compile maps delineating earthquake fault zones and to submit maps to all affected cities, counties and state agencies for review and comment. For the last 44 years, Special Publication 42 has been the vehicle by which the State Geologist, through the California Geological Survey, has informed affected agencies and the general public how and where Alquist-Priolo Earthquake Fault Zones are prepared. This is the twelfth revision of Special Publication 42, which was first issued in December 1973 as an “Index to Maps of Special Studies Zones.” Explanatory text was added in 1975 and subsequent revisions were made between 1976 - 2007. Since 2007, five supplements to Special Publication 42 have been issued to show the locations, names, and release dates of Earthquake Fault Zone maps released between 2012 - 2017. This latest version of Special Publication 42 represents a significant departure from previous versions. Rather than serve simply as a source of background information and an index of 7.5-minute quadrangle maps containing Earthquake Fault Zones, this revised document is specifically intended to provide state-of-the-practice guidelines for affected permitting agencies and their reviewers, as well as for geoscience consulting practitioners representing property owners and developers. Such guidance has previously been presented in California Geological Survey Note 41, “General Guidelines for Reviewing Geologic Reports” and Note 49, “Guidelines for Evaluating the Hazard of Surface Fault Rupture,” which traditionally have been included as appendices to Special Publication 42. The information presented in those notes has been significantly updated, expanded, and incorporated into this new version. As with the zone maps themselves, it is anticipated that this document will continue to be revised as major advances in the sciences associated with surface fault rupture occur. Background material regarding the California Geological Survey’s Fault Evaluation and Zoning Program, which made up the bulk of previous versions of Special Publication 42, has been updated and now appears in Appendix C. Maps of Earthquake Fault Zones are now available in multiple formats. Most recently, these maps have been made available through a web application (https://maps.conservation.ca.gov/cgs/EQZApp/) that allows users to navigate to an individual parcel and determine whether or not it is affected by any of CGS’s regulatory zones (fault rupture, soil liquefaction, or earthquake landslides). Institutional users, such as cities and counties, can access the zone maps on their systems through an interactive web map service: (https://spatialservices.conservation.ca.gov/arcgis/rest/services/CGS_Earthquake_Hazard_Zones) Those who prefer geographic information files (GIS) or portable document format (PDF) versions of maps, or wish to see how the zone maps were prepared through the associated fault evaluation report, can download these from the CGS Information Warehouse: (http://maps.conservation.ca.gov/cgs/informationwarehouse/). IV CONTENTS PREFACE ............................................................................................................................................. IV CONTENTS ........................................................................................................................................... V ILLUSTRATIONS .................................................................................................................................. VII Figures .............................................................................................................................................................................. VII Plates ................................................................................................................................................................................ VII ACKNOWLEDGEMENTS ..................................................................................................................... VIII SECTION 1: DEFINITIONS AND ACRONYMS .......................................................................................... 1 1.1 Definitions .................................................................................................................................................................... 1 1.2 Acronyms ..................................................................................................................................................................... 4 SECTION 2: INTRODUCTION (FOR ALL AUDIENCES) ............................................................................. 5 2.1 Section Outline ............................................................................................................................................................ 5 2.2 Objectives of these Guidelines .................................................................................................................................... 5 2.3 How to use these Guidelines ....................................................................................................................................... 5 2.4 What is surface fault rupture and why is it a hazard? ................................................................................................. 6 2.5 The Alquist-Priolo Earthquake Fault Zoning Act .......................................................................................................... 6 2.6 Rationale for zoning Holocene-active Faults ............................................................................................................... 9 2.7 Roles and responsibilities under the Alquist – Priolo Earthquake Fault Zoning Act ................................................. 10 2.8 Uses and Limitations of Earthquake Fault Zone Maps .............................................................................................. 12 2.9 How to determine if a project is regulated by the Alquist – Priolo Earthquake Fault Zoning Act? ........................... 14 2.10 Relationship of these Guidelines to Local General Plans and Permitting Ordinances ............................................ 14 2.11 Relationship of these Guidelines to the CEQA Process and Other Site Investigation Requirements ..................... 15 2.12 References............................................................................................................................................................... 15 SECTION 3: GUIDELINES FOR LEAD AGENCIES ................................................................................... 17 3.1 Section Outline .......................................................................................................................................................... 17 3.2 Lead agency responsibilities under the Alquist - Priolo Earthquake Fault Zoning Act ............................................. 17 3.3 Lead agency roles and responsibilities in the review of Preliminary EFZ Maps and release of Official EFZ Maps ... 18 3.4 When is a project subject to the Alquist-Priolo Earthquake Fault Zoning Act? ......................................................... 19 3.5 Lead agency roles and responsibilities in the implementation and enforcement of the Alquist-Priolo Earthquake Fault Zoning Act ............................................................................................................................................................... 19 3.6 Fault investigation report filing requirements ......................................................................................................