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Liquefaction potential of unconsolidated sediments in the southern San Francisco Bay Region, California

Open-File Report 73-368

Prepared in cooperation with the Department of Housing and Urban Development
By:
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Abstract

A preliminary map of liquefaction potential of unconsolidated sediments has been made for the southern part of the San Francisco Bay region. Map zones are established on the basis of recent detailed geologic mapping. Liquefaction potential for each zone is estimated from an analysis of lithologic, water-table and standard penetration test data. Due to empirical aspects of the evaluation method, approximations in establishing parameters and the generalizations of limited test data to entire map zones, the liquefaction potential map must be considered as~preliminary and approximate. Nevertheless, the map should serve the intended purpose of generally delineating areas where the probability for liquefaction during a major earthquake is greatest and, hence, areas where special attention should be given to the possibility of liquefaction.


Sediments with the highest potential for liquefaction are clean granular layers within the younger bay sediments. These layers are not everywhere present but commonly occur locally near present and former stream channels. Clean granular beds and layers immediately beneath the younger bay sediments generally have a lesser but significant potential for liquefaction. Younger (Holocene) alluvial deposits have an even lower potential, however, the potential can be locally high in recent channel and overbank deposits. Part of the Holocene unit is normally above water-table and thus would have only a seasonal potential for liquefaction. Older (Pleistocene) alluvial fan deposits have a generally low liquefaction potential. Lateral spreading landslides are commonly associated with liquefaction beneath gentle slopes. Thus. during a major earthquake. slides of this type would probably be the most pervasive damaging effect of liquefaction on the broad alluvial plain surrounding San Francisco Bay.

Geospatial Extents

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Liquefaction potential of unconsolidated sediments in the southern San Francisco Bay Region, California
Series title:
Open-File Report
Series number:
73-368
Year Published:
1973
Language:
English
Publisher:
U.S. Geological Survey
Description:
ii, 23 p.
Number of Pages:
26
Country:
United States
State:
California
Other Geospatial:
San Francisco Bay