RELEASE OF OFFICIAL MAPS OF NEW AND REVISED EARTHQUAKE FAULT ZONES
SEPTEMBER 21, 2012
Thirteen Official Maps of new and revised Alquist-Priolo Earthquake Fault Zones were released on September 21, 2012 to Alameda, Imperial, Riverside, San Diego, and Ventura counties and the cities of Hayward, Oakland, and San Leandro by the California Geological Survey (CGS). These maps are released under the authority of the Alquist-Priolo Earthquake Fault Zoning (AP) Act that was passed following the 1971 San Fernando earthquake. The AP Act is a state law designed to reduce the hazard from surface fault rupture during an earthquake.
Earthquake Fault Zones are regulatory zones that encompass surface traces of active faults that have a potential for future surface fault rupture. The index map shows the general location of maps delineating the new and revised Earthquake Fault Zones within the affected areas of Alameda, Imperial, Riverside, San Diego, and Ventura counties.
New Map Format
These new and revised maps are displayed in a new format. The updated graphical representation shows the location of AP Earthquake Fault Zones and Seismic Hazard Zones (if evaluated) and is collectively referred to as Earthquake Zones of Required Investigation. An electronic version of the zone maps, referred to as a geo-pdf file, can be viewed using Adobe Acrobat Reader. This geo-pdf file consists of multiple layers and gives the user greater flexibility in viewing and displaying the maps. For example, the geo-pdf file contains a shaded relief map, a topographic contour map, and a standard U.S. Geological Survey topographic base map. These layers can be combined, or displayed one at a time. Digital Geographic Information System (GIS) files for both AP Earthquake Fault Zones and Seismic Hazard Zones released by CGS are considered the “Official Maps.” Both GIS and geo-pdf files, as well as conventional pdf files, can be downloaded for the September 21, 2012 release. Seismic Hazard Zone GIS files can be downloaded here.