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​​​​​​​​​​​​Release of Preliminary Maps of Earthquake Fault Zones

 December 15, 2016


Three revised Preliminary Alquist-Priolo Earthquake Fault Zone maps were released on December 15, 2016 to Los Angeles County and the cities of Arcadia, Los Angeles, Monrovia, Pasadena, San Marino, and South Pasadena, 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.

These revised maps show the location of Preliminary AP Earthquake Fault Zones and Seismic Hazard Zones (if evaluated) and are collectively referred to as Earthquake Zones of Required Investigation.  An electronic version of the zone maps, referred to as a GeoPDF file, can be downloaded and viewed using Adobe Acrobat Reader.  This GeoPDF file consists of multiple layers with attributes and gives the user greater flexibility in viewing and displaying the maps. A user guide for the GeoPDF format map can be downloaded here. Digital Geographic Information System (GIS) files for Preliminary AP Earthquake Fault Zones were released by CGS.  Both GIS and GeoPDF files can be downloaded for the December 15, 2016 release.  Seismic Hazard Zone GIS files can also be downloaded here​.


Fault Evaluation Report 7.5 Minute Quadrangles GIS Data
FER 260  ​ Los Angeles
Los Angeles​​
​​​FER 264​   El Monte
Mount Wilson
El Monte​
Mount Wilson