Roughly one quarter of the San Francisco Bay region may
be exposed to liquefaction with the shaking
that has been forecast. The area mapped in the Very High, High
and Moderate categories makes up about 25% of the 9-county
region. Some of the most hazardous areas are beneath our
urban core!
The liquefaction susceptibility mapping is
based on assessments of the potential for liquefaction
in each Quaternary geologic map unit and applied across
the entire area. More detailed evaluation (for example,
for one's house or a particular site) requires more detailed
information, such as geotechnical borings. This would
apply, for example, to areas of artificial fill around
the Bay margins, where many fills are old and poorly engineered,
but others are not.
Map compiled from Knudsen and others,
2000, and Witter and others, 2005 (see how
the map was made).
U.S. Department of the Interior | U.S. Geological Survey
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