What is Soil Liquefaction?
Liquefaction happens when loosely packed sandy or silty materials saturated with water are shaken hard enough to lose strength and stiffness. Liquefied soils behave like a liquid and are responsible for tremendous damage in an earthquake, causing pipes to leak, roads and airport runways to buckle, and building foundations to be damaged.
Official California Seismic Hazards Zone Map
Source: California Geological Survey (CGS) Seismic Hazards Zonation Program
Note: the Lick Observatory quadrangle (Santa Clara County) of this map as been updated by CGS, but is not yet incorporated into the maps on ABAG’s website. Please go directly to the CGS website to view these updated maps.
Interactive Seismic Hazards Zone Map
Google Earth – Export map | Download Google Earth
These maps are State 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. Sellers of properties within a “Zone of Required Investigation” must disclose that fact to prospective buyers.
Liquefaction Hazard Map
Source: ABAG, 2011. The Real Dirt on Liquefaction – Appendix B | 2011 Supplement
Interactive | Static Liquefaction Hazard Map
Mapping Approach – This map shows areas where the ground is susceptible to liquefaction AND that are likely to be shaken hard enough in a particular earthquake to trigger liquefaction. In 2011 this map was updated to incorporate new liquefaction susceptibility and shaking maps. This map is not a substitute for a site-specific investigation by a licensed geologist or geotechnical engineer.
Liquefaction Hazard Maps, USGS Open-File Reports 02-296 and 2008-1270 –
Northwestern Alameda County | Northern Santa Clara County
Liquefaction Susceptibility Map
Source: USGS Open-File Reports 00-444 and 2006-1037
Interactive Liquefaction Susceptibility Map
Google Earth – Export map | Download Google Earth
Mapping Approach – This map shows areas with water-saturated sandy and silty materials that are susceptible to liquefaction if shaken hard enough. This map is not a substitute for a site-specific investigation by a licensed geologist or geotechnical engineer.
What Are the Effects of Liquefaction?
The Real Dirt on Liquefaction, ABAG 2001 – Purchase report and appendices
Northwestern Alameda County | Northern Santa Clara County
The purpose of this report is to serve as a catalyst for understanding and mitigating (through avoidance, engineering, planning and response) the liquefaction hazard in the San Francisco Bay Area. As such, the audience is not the geology or engineering community, but rather those who work for and with the local governments, utilities, businesses, and residents in our region.
Vulnerability and Exposure of the Bay Area
Probability of earthquake-related hazards
Exposure of the Bay Area to liquefaction hazards
Vulnerability of the Bay Area to earthquake-related hazards
More Information
Roads and Airport Runways in Earthquakes
Guidelines for Analyzing and Mitigating Liquefaction in California, Recommended Procedures for Implementation. Southern California Earthquake Center
The writing and production of The Real Dirt on Liquefaction reports and maps were funded by Grant Nos. 1434-HQ-97-GR-03048 and 1434-HQ-97-GR-03121 from the U.S. Geological Survey (USGS), as well as by the Association of Bay Area Governments and William Lettis & Associates. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding agencies. ABAG, the Association of Bay Area Governments, is the regional planning and services agency for the nine-county San Francisco Bay Area. Source: The Real Dirt on Liquefaction documentation prepared by ABAG in 2001.