Earthquake Zones of Required Investigation

The California Earthquake Hazards Zone Application ("EQ Zapp") is an onlin​e map that allows anyone with a computer, tablet or smartphone to conveniently check whether a property is in an earthquake hazard zone.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: fault rupture, where the surface of the earth breaks along a fault;liquefaction, in which the soil temporarily turns to quicksand and cannot support structures; andearthquake-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.