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While many Bay Area residents are familiar with the hazards associated with earthquakes,
there are other hazards that can impact the region. This map application is intended to
provide general information related to hazard potential, planning areas, and impact severity.

**Disclaimer**
The information provided is intended for planning use only and is not intended to be
site-specific. Rather, it depicts general risks within neighborhoods and the relative risks
from community to community. Hazard levels are less likely to be accurate if your
neighborhood is on, or near, the border between zones. The information in this map
application is not a substitute for a site-specific investigation by a licensed professional.

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St. Helena or Walnut Creek]


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Map LayerDescriptionSource
Earthquake Hazards
Alquist-Priolo Fault ZonesEarthquake fault zones mapped to comply with the Alquist-Priolo Earthquake Fault Zoning Act (a state law designed to reduce the hazard from surface fault rupture during and earthquake). The fault zones encompass surface traces of active faults that have a potential for future surface fault rupture.California Department of Conservation
Last updated: September 2012
Click 'View/Download AP Maps' to open service for downloading shapefiles
Earthquake Shaking ScenariosShaking severity modeled for potential events in the San Francisco Bay Area. The models assume a fault segment and rupture length and uses ground motion attenuation relationships to estimate ground motion at locations away from the fault.United States Geological Survey
Last updated: 2008
No data download available at this time.
Earthquake Shaking PotentialShows an estimate of the likelihood of earthquake ground motions, based on a probabilistic seismic hazard analysis. The probabilities are calculated by projecting earthquake rates based on earthquake history and fault slip rates. The results are the probability that an earthquake of a specified magnitude will occur on a fault or within an area.California Geological Survey and United States Geological Survey
Last updated: 2003
Earthquake-Induced Landslide Study ZonesThis hazard layer relates State-mandated regulatory maps that show "Zones of Required Investigation" for landslide hazard areas. It does not depict different degrees of hazard, rather it identifies zones within which site specific studies will be required for new construction. This information is also used in real estate transactions where sellers of property within a "Zone of Required Investigation" must disclose that fact to prospective buyers.California Geological Survey (CGS)
Click 'View/Download AP Maps' to open service for downloading shapefiles
Liquefaction Study ZonesThis hazard layer relates State-mandated regulatory maps that show "Zones of Required Investigation" for liquefaction hazard areas. It does not depict different degrees of hazard, rather it identifies zones within which site specific studies will be required for new construction. This information is also used in real estate transactions where sellers of property within a "Zone of Required Investigation" must disclose that fact to prospective buyers.California Geological Survey (CGS)
Click 'View/Download AP Maps' to open service for downloading shapefiles
Liquefaction SusceptibilityAreas susceptible to liquefaction based on analysis of underlying geologic materials. The feature set for this hazard layer was compiled using two USGS reports, a 2000 report covering the entire Bay Area and a 2006 update for the core of the region.United States Geological Survey
Last updated: 2006
Data download (2000 shapefile)
Data download (2006 shapefile)

Flooding Hazards
Tsunami Evacuation AreaDeveloped for the purpose of hazard preparedness planning by coastal government agencies, this feature set does not represent inundation from a single scenario event. It was created by combining inundation results for a suite of realistic local and distant earthquakes and hypothetical extreme undersea, near-shore landslides, representing the worst-case scenario at any given location. Data for the north coast of Sonoma County has not been developed yet.California Geological Survey
Last updated: December 2009
Download (PDF maps)
FEMA Flood ZonesNational Flood Hazard Layer (NFHL) data showing areas at risk of 100-year and 500-year floods. The areas shown do not assume a particular water depth, only that the area is susceptible to flooding.Federal Emergency Management Agency
As of 3/31/2014
Data download (Select Product Type: NFHL Data) (shapefile)

Wildfire Hazards
Wildfire Perimeters (1950-2011)Wildfire perimeters compiled through the Fire and Resource Assessment Program as part of the California Fire Plan. Generally, the feature set includes timber fires of at least 10 acres, brush fires of at least 50 acres, and grass fires at least 300 acres in size, however, it also includes wildland fires that destroy three or more structures and wildland fires that cause $300,000 or more in damage even if they do not meet the minimum size limits of the main categories. It is intended to provide a reasonable view of the spatial distribution of past large fires, however, this feature set is incomplete in many respects and users must exercise caution to avoid inaccurate or erroneous conclusions.California Department of Forestry and Fire Protection
Last updated: January 2012
Download (geodatabase)
Wildfire ThreatHazard layer displays the relative risk wildlands may experience a wildfire.California Department of Forestry and Fire Protection
Last updated: January 2005
Data download (raster)
Wildland-Urban Interface - Fire Threatened CommunitiesHazard layer displays communities at risk of wildland fires.California Department of Forestry and Fire Protection
Last updated: January 2003
No data download available at this time.

Landslide Hazards
Existing LandslidesThe best available predictor of where movement of slides and earth flows might occur is the distribution of past movements. Past landslides can be recognized from their distinctive topographic shapes. Most show no evidence of recent movement and are not currently active, but some portion of them may become active in any one year. This hazard layer shows areas where landslides have occurred in the past.United States Geological Survey
Last updated: February 1998
Data download (ArcInfo Coverage)
Debris Flow Source AreasDebris flows (mudslides) are fast moving, down-slope flows that may include rocks, vegetation, and other debris. This map service shows areas that are likely to produce debris flows.United States Geological Survey
Last updated: 1997
Data download (ArcInfo Coverage)