California Geological Survey Unveils Web Application to Help Public Locate Earthquake Hazard Zones

​News Release #2018-01
March 21, 2018

SACRAMENTO – A new online tool from the California Geological Survey (CGS) will allow prospective home-buyers and others to conveniently check -- free of charge -- whether property is in a regulatory earthquake hazard zone.

When existing homes and structures within zones are sold, disclosure is required. For new construction or significant remodels, site-specific geologic studies are required so builders can avoid the hazards or incorporate mitigation features. CGS has given the Earthquake Hazards Zone Application the nickname “EQ Zapp.” 

“We’ve created the Earthquake Hazard Zone web application as a public service because home-buyers now are often well into the real estate transaction before they learn that the property falls within a hazard zone,” said Dr. John Parrish, the State Geologist of California and head of CGS.

“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.”

CGS’ earthquake hazard zones define areas subject to three distinct types of geologic ground failures:
landslides; liquefaction, in which the soil temporarily turns to quicksand and cannot support structures; and fault rupture, where the surface of the earth breaks along a fault, either vertically or laterally, which can damage the stability of overlying structures.

“The EQ Zapp includes the CGS regulatory zone maps and incorporates land parcels statewide,” said Tim McCrink, who heads the CGS Seismic Hazards Program. “This will help people who are looking to purchase property identify local hazardous ground conditions; they’ll have to determine whether they’re comfortable being within one of the zones. There is also a demand for the ease of access this provides among real estate agents, who can more easily find out if a disclosure is necessary; among planners and developers, who can readily determine whether a proposed development project is within a zone; and agencies such as the
Governor’s Office of Emergency Services and the California Earthquake Authority.

“We really tried to make the earthquake zones understandable through this web application -- in particular, the frequently asked questions section explains a lot about how the hazard zones work,” McCrink added.

Using the EQ Zapp, individuals will be able to type in an address or use the location capability of their smart phone or tablet to determine whether a property lies within any of CGS’s mapped earthquake hazard zones. It will also tell users if CGS has not yet evaluated those hazards in that area.

“The California Department of Conservation is to be applauded for developing and launching a new consumer app that allows users to type in an address and see what earthquake hazards might underlie and possibly affect the property,” California Bureau of Real Estate Commissioner Wayne Bell said. “Earthquake safety is very important in California, and this is information that can help consumers gain a greater understanding of the earthquake susceptibilities of properties they are interested in buying.

“Currently, there are environmental and earthquake hazard disclosure requirements for sellers of residential real estate. This new app can be used by sellers and by buyers of both residential and commercial properties to learn more about potential earthquake hazards.”

These earthquake hazard zones are also available to be viewed/downloaded as PDF maps and documents or as geographic information system (GIS) Shapefiles through the CGS Information Warehouse​. They are also available as web services that can be
incorporated into a GIS, and metadata pages are also available. Visit the CGS page for more info and links.

Don Drysdale
(916) 323-1886