California Department of Conservation

05/21/2026 | News release | Distributed by Public on 05/21/2026 11:08

New preliminary Earthquake Zones of Required Investigation

Preliminary Earthquake Zones of Required Investigation

Page Image
Page Content

On this page:

Preliminary Earthquake Fault Zones

Index maps showing the general areas affected by the Earthquake Fault Zones in this release. Click an image to open a larger version in a new window.

MAY 21, 2026 - The California Geological Survey released new technical reports describing preliminary Alquist-Priolo Earthquake Fault Zones for public review. The zones in this release affect the cities of Berkeley, Concord, El Cerrito, Fremont, Hayward, Milpitas, Oakland, Richmond, San Leandro, San Pablo, Union City, Walnut Creek, and the counties of Alameda, Contra Costa, and Santa Clara.

  • Preliminary Fault Evaluation Report 267: The Hayward Fault in Contra Costa, Alameda, and Santa Clara Counties, California
  • Preliminary Fault Evaluation Report 276: The Concord Fault Zone in Contra Costa County, California

The reports, which include maps of the preliminary zones, are available as PDF files. To download them, click the button provided below.

NOTE: Clicking the button will redirect you to the California Department of Conservation's FileRequest site, where you must select the reports you want, then provide an email address where we will send you perishable links for downloading the reports.

Earthquake Fault Zones are regulatory zones that encompass surface traces of active faults that have a potential for future surface fault rupture. These zones are identified under the authority of the Alquist-Priolo Earthquake Fault Zoning Act (Alquist-Priolo Act) that was passed following the 1971 San Fernando earthquake. The Alquist-Priolo Act is a state law designed to reduce the hazard from surface fault rupture during an earthquake.

Related Reference Material

  • Reference Guide for Assessing Fault Rupture Hazards (Special Publication 42: Earthquake Fault Zones - A Guide for Government Agencies, Property Owners/Developers, and Geoscience Practitioners for Assessing Fault Rupture Hazards in California). This document contains technical guidelines for evaluating surface fault rupture hazards and for reviewing geologic reports.

Preliminary Seismic Hazard Zones

Index maps showing the general areas affected by the Seismic Hazard Zones in this release. Click an image to open a larger version in a new window.

MAY 21, 2026 - The California Geological Survey released new technical reports describing preliminary Seismic Hazard Zones for public review. The zones in this release affect the cities of Cotati, Petaluma, Rohnert Park, Sacramento, and the counties of Alameda, Contra Costa, Placer, Sacramento, Sonoma, Sutter, and Yolo.

  • Preliminary Seismic Hazard Zone Report 144: Seismic Hazard Zone Report for the Tassajara 7.5-Minute Quadrangle, Contra Costa and Alameda Counties, California
  • Preliminary Seismic Hazard Zone Report 145: Seismic Hazard Zone Report for the Cotati 7.5-Minute Quadrangle, Sonoma County, California
  • Preliminary Seismic Hazard Zone Report 146: Seismic Hazard Zone Report for the Taylor Monument and Rio Linda 7.5-Minute Quadrangles, Placer, Sacramento, Sutter and Yolo Counties, California

The reports, which include maps of the preliminary zones, are available as PDF files. To download them, click the button provided below.

NOTE: Clicking the button will redirect you to the California Department of Conservation's FileRequest site, where you must select the reports you want, then provide an email address where we will send you perishable links for downloading the reports.

Seismic Hazard Zones are regulatory zones that encompass areas that have a potential for future ground deformations caused by liquefaction or landslides. These zones are identified under the authority of the Seismic Hazards Mapping Act that was passed following the 1989 Loma Prieta earthquake. The Seismic Hazards Mapping Act is a state law designed to reduce the hazards from soil liquefaction and landslides during an earthquake.

Related Reference Material

  • Reference Guide for Evaluating Seismic Hazards (Special Publication 117A: Guidelines for Evaluating and Mitigating Seismic Hazards in California). This document constitutes the guidelines for evaluating seismic hazards other than surface fault rupture, and for recommending mitigation measures as required by Public Resources Code Section 2695(a).

Review Comment Period

The May 21, 2026 release date begins a 90-day public comment period designed to provide the opportunity for the State Mining and Geology Board to receive technical review comments that may have a bearing on the preliminary zones. Comments must be sent to the State Mining and Geology Board before August 19, 2026. Please direct comments to:

Jeffrey Schmidt, Executive Officer
State Mining and Geology Board
715 P Street, MS 1909
Sacramento, CA 95814
(916) 322-1082
[email protected]

As required by the Alquist-Priolo Earthquake Fault Zoning Act, the State Mining and Geology Board will hold a public hearing near the end of the 90-day review period for the preliminary Earthquake Fault Zones. Questions related to the public hearing should be directed to the State Mining and Geology Board.

RELATED: Archive of CGS Publication Announcements

‭(Hidden)‬ Custom CSS

California Department of Conservation published this content on May 21, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on May 21, 2026 at 17:08 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]