On February 26, 2002 the Santa Clara Board of Supervisors officially adopted the County Geologic Hazards Zones (GHZ) and the revised ordinance.
The GHZs were produced by combining information from a variety of published and unpublished sources regarding the location and extent of possible faults, landslides, compressible soils, dike failure flooding, and liquefaction. The County GHZs identify areas where available information suggests specific geologic hazards may be present. In those areas, the ordinance requires that the owner/applicant submit a geologic report (prepared and signed by a Certified Engineering Geologist [CEG]) for review by the County Geologist prior to approval of certain applications for construction.
List of Certified Engineering Geologists (PDF) - who are licensed by the State of California and have indicated their willingness to work on individual sites located in Santa Clara County.
When the Board adopted the County GHZs in 2002, the State Geologist had already released four official Seismic Hazard Zones Maps, the landslide and liquefaction zones on those maps were incorporated into the County GHZs. At that time, the Board of Supervisors also adopted a provision that the County GHZs would be revised to include California's Seismic Hazard Zones (SHZ) when ever the State Geologist released additional SHZ maps.
The following table indicates the dates of release of State maps and data, as well as the dates that the County Hazard Zones and maps were revised.
Name of Quadrangle
Date of Release of
Date of Revision of
|San Jose East||01/17/2001||02/26/2002|
|San Jose West||02/07/2002||02/26/2002|
|Santa Teresa Hill||08/14/2003||08/18/2003|
|Castle Rock Ridge||08/11/2005||08/15/2005|
** Milpitas Quad was re-issued on 10/19/2004 with areas in Alameda County added.
*** Mountain View Quad was re-issued on 6/20/2003 with areas in Alameda County added and 10-18-2006 with areas in San Mateo County added.
NOTE: Specific portions of the County LANDSLIDE and LIQUEFACTION Hazard Zones were revised on the dates indicated. The last revision was made on December 5, 2012 when all five County Geologic Hazard Zones were consolidated within a single multi-layer pdf. (Viewing of various layers requires Adobe Acrobat Reader 9.0 or higher.)
Future releases of additional State SHZ maps will be followed by revisions of the County Geologic Hazard Zones and maps that will be posted on this website.
To download the maps, right click on the following link and select 'save as' and save it where ever you like on your computer (viewing it in your browser will not show the hazard layers):
County Geologic Hazard Zones (31.2 MB)
(Potential Fault Rupture, Landsliding, Liquefaction, Compressible Soils, and Dike Failure Flooding).
Directions for Viewing Layered Geologic Hazard Zone from the downloaded PDF
(open the file using Adobe Acrobat Reader version 9.0 or higher):
- Click on the 'Layers' icon to open the 'Layers' column on the far left (It will be the third icon from the top).
- Navigate to the desired page of interest (either the main index page [Page A], or one of the grid pages as indicated on the index.
- In the 'Layers' column, click on the '+' sign in front of the selected page to expand the page options.
- Click on the '+' sign in front of 'Focus Map' folder to expand the folder contents.
- Click on the check box to the left for each of the Hazard Layers (such as Fault Rupture Hazard Zones, Dike Failure Hazard Zones, etc.) This will put an eye in the check box and turn on that specific layer in the map.
- If the specific map page does not one of the Geologic Hazard Zones, that Hazard Zone will not appear as an option below the 'Focus Map' folder.
Obtaining State Data and Maps
For information about geologic hazard zones maps produced by the California Geological Survey, go to the State of California's websites at:
Maps produced by the State of California may be ordered from:
149 Second Street
San Francisco, CA 94105