Source: California Geologic Survey (CGS) Seismic Hazards Zonation Program
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This map is derived from State-mandated regulatory maps that show “Zones of Required Investigation” for landslide (and liquefaction) hazard. They do not depict different degrees of hazard, rather they identify zones within which site specific studies will be required for new construction. These zone maps also are used in real estate transactions – sellers of properties within a “Zone of Required Investigation” must disclose that fact to prospective buyers.
Rainfall-Induced Landslides :: Existing Landslides
Source: USGS, updated 1998. Summary Distribution of Slides and Earth Flows
This map shows areas where landslides have occurred in the past.
Rainfall-Induced Landslides :: Debris Flow Source Areas
Source: USGS, 1997. Map Showing Principal Debris Source Flow Areas in the San Francisco Bay Region
This map shows areas that are likely to produce debris flows (mudslides). Debris flows are fast moving, down-slope flows that may include rocks, vegetation, and other debris.