• Preliminary maps of Quaternary deposits and liquefaction susceptibility, nine-county San Francisco Bay region, California: a digital database

    Metadata Updated: March 22, 2021

    This report presents a preliminary map and database of Quaternary deposits and liquefaction susceptibility for the nine-county San Francisco Bay region, together with a digital compendium of ground effects associated with past earthquakes in the region. The report consists of (1) a spatial database of fivedata layers (Quaternary deposits, quadrangle index, and three ground effects layers) and two text layers (a labels and leaders layer for Quaternary deposits and for ground effects), (2) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility), (3) a text describing the Quaternary map, liquefaction interpretation, and the ground effects compendium, and (4) the databse description pamphlet. The nine counties surrounding San Francisco Bay straddle the San Andreas fault system, which exposes the region to serious earthquake hazard (Working Group on California Earthquake Probabilities, 1999). Much of the land adjacent to the Bay and the major rivers and streams is underlain by unconsolidated deposits that are particularly vulnerable to earthquake shaking and liquefaction of water-saturated granular sediment. This new map provides a modern and regionally consistent treatment of Quaternary surficial deposits that builds on the pioneering mapping of Helley and Lajoie (Helley and others, 1979) and such intervening work as Atwater (1982), Helley and others (1994), and Helley and Graymer (1997a and b). Like these earlier studies, the current mapping uses geomorphic expression, pedogenic soils, and inferred depositional environments to define and distinguish the map units. In contrast to the twelve map units of Helley and Lajoie, however, this new map uses a complex stratigraphy of some forty units, which permits a more realistic portrayal of the Quaternary depositional system. The two colored maps provide a regional summary of the new mapping at a scale of 1:275,000, a scale that is sufficient to show the general distribution and relationships of the map units but cannot distinguish the more detailed elements that are present in the database. The report is the product of years of cooperative work by the USGS National Earthquake Hazards Reduction Program (NEHRP) and National Cooperative Geologic Mapping Program, William Lettis and & Associates, Inc. (WLA) and, more recently, by the California Division of Mines and Geology as well. An earlier version was submitted to the Geological Survey by WLA as a final report for a NEHRP grant (Knudsen and others, 2000). The mapping has been carried out by WLA geologists under contract to the NEHRP Earthquake Program (Grants #14-08-0001-G2129, 1434-94-G-2499, 1434-HQ-97-GR-03121, and 99-HQ-GR-0095) and with other limited support from the County of Napa, and recently also by the California Division of Mines and Geology. The current map consists of this new mapping and revisions of previous USGS mapping.

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    Dates

    Metadata Date June 13, 2016
    Metadata Created Date March 22, 2021
    Metadata Updated Date March 22, 2021
    Reference Date(s) January 1, 2000 (publication)
    Frequency Of Update asNeeded

    Metadata Source

    Harvested from USGS-Harvest

    Graphic Preview

    Quaternary Deposits Map (5.4MB)

    Additional Metadata

    Resource Type Dataset
    Metadata Date June 13, 2016
    Metadata Created Date March 22, 2021
    Metadata Updated Date March 22, 2021
    Reference Date(s) January 1, 2000 (publication)
    Responsible Party USGS Earthquake Hazards Team (Point of Contact)
    Contact Email
    Guid
    Access Constraints Use Constraints: Use is limited by the 1:24,000 - 1:100,000 scale spatial resolution of the data., Access Constraints: None
    Bbox East Long -123.625
    Bbox North Lat 38.866667
    Bbox South Lat 36.866667
    Bbox West Long -121.125
    Coupled Resource
    Frequency Of Update asNeeded
    Graphic Preview Description Quaternary Deposits Map (5.4MB)
    Graphic Preview File http://pubs.usgs.gov/of/2000/of00-444/of00-444_7b.pdf
    Graphic Preview Type PDF
    Licence This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
    Metadata Language eng; USA
    Metadata Type geospatial
    Progress completed
    Spatial Data Service Type
    Spatial Reference System
    Spatial Harvester True

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