Preliminary Release Announcements

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Preliminary Review Maps of Proposed New and Revised Earthquake Fault Zones

May 23, 2024

The California Geological Survey released preliminary review maps and reports of proposed new and revised Alquist-Priolo Earthquake Fault Zones to the cities of Palo Alto and Ridgecrest, the towns of Portola Valley and Woodside, and the counties of Inyo, Kern, Los Angeles, San Bernardino, San Mateo, and Santa Clara.

The Earthquake Fault Zone maps in this release cover the following quadrangles in Los Angeles County: Burnt Peak, Lake Hughes, and Del Sur.
Index maps showing outlines of the Earthquake Fault Zone maps in this release. Click an image to open a larger version in a new window.

Earthquake Fault Zones are regulatory zones that encompass surface traces of active faults that have a potential for future surface fault rupture. The index maps below show the locations of the quadrangles included with this release.

These maps are released 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.

The maps and reports are available as PDF files, which can be viewed using Adobe Acrobat Reader. To download these maps and reports, follow the links provided below.


Related Reference Material

Preliminary Review Maps of Proposed New Seismic Hazard Zones

May 23, 2024

The California Geological Survey released preliminary review maps and reports of proposed new Seismic Hazard Zones to the cities of Danville, Hercules, Lafayette, Martinez, Moraga, Orinda, Pinole, Richmond, San Ramon, and Walnut Creek, and the county of Contra Costa. The index map below shows the locations of the quadrangles included with this release.

The Seismic Hazard Zone maps in this release cover the following quadrangles in Contra Costa County: Benicia, Briones Valley, Oakland East, Las Trampas Ridge, Hayward, Dublin, and Livermore.
Index map showing outlines of the Seismic Hazard Zone maps in this release. Click the image to open a larger version in a new window.

Seismic Hazard Zones are regulatory zones that encompass areas that have a potential for future ground deformations caused by liquefaction or landslides.

These maps are released 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.

The maps and reports are available as PDF files, which can be viewed using Adobe Acrobat Reader. To download these maps and reports, follow the links provided below.


Related Reference Material

Review Comment Period

The May 23, 2024 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 proposed maps. Comments must be sent to the State Mining and Geology Board before August 21, 2024. Please direct comments to:

Jeffrey Schmidt, Executive Officer
State Mining and Geology Board
715 P Street, MS 1909
Sacramento, CA 95814
(916) 322-1082
smgb@conservation.ca.gov

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 proposed revised Earthquake Fault Zones. Questions related to the public hearing should be directed to the State Mining and Geology Board.

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