The Seismic Hazards Program delineates areas prone to ground failure and other earthquake-related hazards including soil liquefaction (the failure of water-saturated soil), earthquake-induced landslides, surface fault rupture, and tsunami inundation. Cities and counties are required to use these maps in their land-use planning and building permit processes so that these hazards are identified and mitigated for development projects prior to the next major earthquake. Additionally, the program reviews and provides comments on geologic and seismic hazards that apply directly to the design and construction of essential and critical facilities around the state. These facilities include schools, hospitals, nuclear power plants, hazardous waste repositories, and others, typically under contract to other state agencies. The program compiles information about past earthquakes, the potential for earthquakes on major faults, and rates of deformation across California to estimate the potential for future earthquakes. The Seismic Hazards Program works closely with the U.S. Geological Survey to produce earthquake shaking maps that are used in development of building codes and in earthquake damage and loss estimates.
Functions and Products of the Seismic Hazards Program
The Alquist-Priolo Earthquake Fault Zoning Act (1972) and the Seismic Hazards Mapping Act (1990) direct the State Geologist to delineate regulatory "Zones of Required Investigation" to reduce the threat to public health and safety and to minimize the loss of life and property posed by earthquake-triggered ground failures. Cities and counties affected by the zones must regulate certain development projects within them. These Acts also require sellers of real property (and their agents) within a mapped hazard zone to disclose at the time of sale that the property lies within such a zone. Studies of faults result in estimates of maximum earthquake magnitudes and long-term slip rates that are the basic input for seismic hazard calculations. Consensus values are compiled by CGS in cooperation with USGS.
Zones of required investigation for possible earthquake faulting, landslides, and liquefaction are delineated and distributed to cities, counties, and state construction agencies to help identify where higher building standards may be necessary for safe development. They include Alquist-Priolo Earthquake Fault Zones, Liquefaction Zones, and Landslide Zones.
Seismic hazards are calculated considering consensus values for earthquake rates based on earthquake history, fault slip rates, and site soil types. The seismic hazard information is combined considering the potential for earthquakes on all seismic sources, and the level of ground shaking that would be caused by those earthquakes. The result is expressed as the level of ground shaking (expressed as a percentage of gravity) that on average occurs every 500 years. These statewide estimates of seismic hazards can then be used to estimate the potential of future earthquake losses.
CGS reviews a number of environmental documents and provides comments relating to geologic hazards and issues that apply directly to assessing the potential impacts of land-use modification. As part of this process, CGS provides site reviews on consulting reports in geology, seismology, and geotechnical engineering for public school and hospital construction.
Seismic Hazard Maps, Reports & GIS Data
Find and download the following products through our
Information Warehouse: Regulatory Maps tool.
Earthquake Zones of Required Investigation: Maps showing faults, fault traces, liquefaction zones and earthquake-induced landslide zones. Available as PDF and GIS Data.
Seismic Hazard Zone Reports and
Fault Evaluation Reports: these reports are provided to accompany and support the Earthquake Zones of Required Investigation maps. They summarize the methods and sources of information used to prepare the maps. Available as PDF.
Geologic/Geotechnical Report Curation
The Policies and Criteria of the State Mining and Geology Board, with respect to the Alquist-Priolo Earthquake Fault Zoning Act (California Code of Regulations, Section 3603(f)), requires lead agencies to file copies of geologic reports of fault studies with the State Geologist within 30 days of its approval. Similarly, the Seismic Hazards Mapping Act (Section 2697(a)) requires cities and counties to submit a copy of each approved geologic/geotechnical report, prepared as a result of the presence of a Seismic Hazard Zone, to the State Geologist within 30 days of its approval.
Upload Geologic/Geotechnical Reports
The California Geological Survey strongly encourages that these reports and associated documentation of approval be submitted in digital format (PDF, MS Word, etc.) through the link at the bottom of this page.
Single File Upload
To upload a single file—or multiple files one at a time—Click the button
at the bottom of this page.
Multiple File Upload
If you wish to upload multiple files or entire folders, please click the following to request a direct link to the Seismic Hazards Box.com upload folder. Include a return e-mail address if different than the sent from address. A Box.com account is required to upload files through this link.
Request access to CGS Box account:
Feedback is welcome. Please use the above e-mail link to submit comments or questions.