Liquefaction Maps of the San Francisco Bay Area

Maps of liquefaction hazard are used to show how the hazard differs from place to place, the likelihood of liquefaction in different earthquake scenarios, and to define hazard zones for regulatory purposes. Basic information used in making these regional maps includes the distribution of different kinds of geologic materials, estimates of depth to ground water, geotechnical borings, and predicted levels of shaking during future earthquakes. Scientists continue to develop methods to characterize the hazard, particularly at the site-investigation level, while maps based on current methods provide regional estimates and regulatory tools.

Susceptibility Map
Map of liquefaction susceptibility that shows the varying susceptibility in different parts of the region. Susceptibility is delineated in five units from Very High to Very Low hazard. Roughly one quarter of the San Francisco Bay region may be exposed to liquefaction — the area mapped in the Very High, High and Moderate categories makes up about 25% of the 9-county region.
Maps of "Zones of Required Investigation"
These maps prepared by the California Geological Survey are State-mandated regulatory maps that show "Zones of Required Investigation" for liquefaction (and landslide) 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.

Additional Liquefaction Hazard Maps
- USGS Earthquake Hazards Program
  USGS scientists have developed liquefaction hazard maps of the Oakland, Berkeley and Alameda areas. These maps make use of more than 200 Cone Penetration Test soundings and show the relative hazards from earthquakes on the Hayward fault. The maps predict the approximate percentage of each designated area that will liquefy and show surface manifestations of liquefaction (such as sand boils and ground cracking).
- Association of Bay Area Governments
  This regional agency (ABAG) provides maps of liquefaction hazards for the nine-county San Francisco Bay Region for specific earthquake scenarios. These maps include liquefaction susceptibility maps and liquefaction hazard maps, both of which are available using interactive Web-based GIS tools.