EQ Zapp: California Earthquake Hazards Zone Application

With EQ Zapp, you can type in an address or use the location capability of your computer or mobile device to determine whether a property lies within any of CGS’s mapped earthquake hazard zones.​ It will also tell you if CGS has not yet evaluated the hazards in that area.

Earthquake hazard zones define areas subject to three distinct types of geologic ground failures: 

1. fault rupture, where the surface of the earth breaks along a fault;
2. liquefaction, in which the soil temporarily turns to quicksand and cannot support structures; and
3. earthquake-induced landslides.

Although strong ground shaking is responsible for most earthquake-related damage, these zones identify areas where earthquake hazards other than structural shaking — specifically ground failures during an earthquake — are more likely.​ The zones trigger geologic and engineering investigations that can identify and mitigate the ground failure hazard before construction begins, thereby making the structure itself more resilient to potential shaking.

In California, there are environmental and earthquake hazard disclosure requirements for sellers of residential real estate. EQ Zapp can be used by prospective sellers and buyers of both residential and commercial properties to learn more about potential earthquake hazards. Additionally, for new construction or significant remodels, site-specific geologic studies are required so builders can avoid known hazards or incorporate mitigation features.

The earthquake hazard zone data are also available to be viewed/downloaded as PDF maps and reports, or as geographic information system (GIS) shapefiles through the CGS Information Warehouse. You can also explore our available GIS data through the Geologic Hazards Data Viewer and Data List.

Important notes regarding the information contained in the California Earthquake Hazards Zone Application

1. The map may not show all faults that have the potential for surface fault rupture, either within the Earthquake Fault Zones or outside their boundaries. Additionally, the map may not show all areas that have the potential for liquefaction, landsliding, strong earthquake ground shaking or other earthquake and geologic hazards. Also, a single earthquake capable of causing liquefaction or triggering landside failure will not uniformly affect the entire area zoned.

2. Faults shown are the basis for establishing the boundaries of the Earthquake Fault Zones.

3. The identification and location of faults are based on the best available data. However, the quality of data used is varied. Traces have been depicted as accurately as possible at a map scale of 1:24,000.

4. Liquefaction zones may also contain areas susceptible to the effects of earthquake-induced landslides. This situation typically exists at or near the toes of existing landslides, downslope from rockfall or debris flow source areas, or adjacent to steep stream banks.

5. Landslide zones on the map were determined, in part, by adapting methods first developed by the U.S. Geological Survey (USGS). Landslide hazard maps prepared by the USGS typically use experimental approaches to assess earthquake-induced and other types of landslide hazards. Although aspects of these new methodologies may be incorporated in future CGS seismic hazard zone maps, USGS maps should not be used as substitutes for Official CGS Seismic Hazard Zones maps.

6. Information on the map is not sufficient to serve as a substitute for the geologic and geotechnical site investigations required under Chapters 7.5 and 7.8 of Division 2 of the California Public Resources Code.

7. Seismic Hazard Zones identified on the map may include developed land where delineated hazards have already been mitigated to city or county standards. Check with your local building/planning department for information regarding the location of such mitigated areas.

8. The parcel data provided on the map are updated semi-annually and may be outdated at the time they are viewed on this application. Please check with the local lead agency for the most up-to-date parcel information.

9. DISCLAIMER: The State of California and the Department of Conservation make no representations or warranties regarding the accuracy of the earthquake hazard zones, or the data from which these zones were derived. Neither the State nor the Department shall be liable under any circumstances for any direct, indirect, special, incidental or consequential damages with respect to any claim by any user or any third party on account of or arising from the use of this information. In addition, the use of maps, related data, or other information that the Department may furnish does not limit, abridge, or necessarily fulfill any obligation for disclosure created by the Alquist-Priolo Earthquake Fault Zoning Act, the Seismic Hazards Mapping Act, or any other provision of law.