CGS Preliminary Maps and Reports

Announcement of Preliminary Review Maps of New Seismic Hazard Zones - October 4, 2018

Preliminary Review Maps of new Seismic Hazard Zones were released by the California Geological Survey (CGS) on October 4, 2018 to the cities of Antioch, Belmont, Brentwood, Burlingame, Concord, Half Moon Bay, Hillsborough, Millbrae, Oakley, Pacifica, Pittsburg, Redwood City, San Bruno, San Carlos, the towns of Portola Valley and Woodside, and the counties of Contra Costa and San Mateo. 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.

Seismic Hazard Zones are regulatory zones identifying areas that have a potential for future ground deformations caused by liquefaction or landslides. The index maps below (Figure 1) shows the general location of maps delineating the Preliminary Seismic Hazard Zones within the affected counties.

Review Comment Period

The October 4, 2018 release date begins a 90-day public comment period designed to provide an opportunity for affected lead agencies and the general public to provide information to the State Mining and Geology Board technical that may have a bearing on the content of proposed Seismic Hazard Zone maps. Comments should be sent to the State Mining and Geology Board before January 2, 2019. Comments should be addressed to:

Jeffrey Schmidt, Executive Officer
State Mining and Geology Board
801 K Street, MS 20-15 Sacramento, CA 95814
(916) 322-1082

The State Mining and Geology Board will hold a public hearing near the end of the 90-day review period. For more information on the date and location of the public hearing, contact the State Mining and Geology Board.

Figure 1: Index maps of affected quadrangles in Contra Costa and San Mateo counties.

Preliminary Maps of Seismic Hazard Zones

Antioch North, 2018
Report (SHZR 125)
Antioch South, 2018
Report (SHZR 126)
Honker Bay, 2018
Report (SHZR 127)
Montara Mountain, 2018
Report (SHZR 128)