Service Description: This layer represents liquefaction potential for soil in Napa County. The 2006 report “Maps of Quaternary deposits and liquefaction susceptibility in the central San Francisco Bay region, California” contains a spatial database of the Quaternary deposits scored for susceptibility to liquefaction. Napa County GIS staff extracted data relevant for county use. Our layer is not fully reflective of the spatial scope or number of fields in the source dataset. Full metadata of the report and contents in its entirety can be located here: http://pubs.usgs.gov/of/2006/1037/
Originally published in 2004 and updated in 2025, this county layer initially used data solely from the USGS report 00-444 dataset. The 00-444 report was a preliminary release of an anticipated future report-- that at the time of Napa County’s publishing of this layer in 2004-- was not expected to be out for another two years. The layer had remained unchanged from its original 2004 publishing until 2025 when it was updated as part of a wider county boundary update effort by the PBES GIS team.
The new USGS report (2006-1037) released in 2006, and its dataset superseded the previous preliminary data. In early 2025, the county PBES GIS team took this new data and cut it to 500 feet surrounding the county boundaries to replace existing geometry and data. Northernmost and Northeastern areas of the county liquefaction layer still retain boundaries and definitions from report 00-444, due to the final release having a smaller spatial spread than the preliminary release.
Below is additional information taken from source metadata. Some portions have been removed since it’s irrelevant to the county layer:
This report presents a map and database of Quaternary deposits and liquefaction susceptibility for the urban core of the San Francisco Bay region. It supersedes the equivalent area of U.S. Geological Survey Open-File Report 00-444 (Knudsen and others, 2000), which covers the larger 9-county San Francisco Bay region. (…) The nine counties surrounding San...
Service ItemId: 150562345e564e1885042228a1acc024
Has Versioned Data: false
Max Record Count: 2000
Supported query Formats: JSON
Supports applyEdits with GlobalIds: False
Supports Shared Templates: True
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Description: Approximately 1800 polygons that show the Quaternary deposits and liquefaction susceptibility for Napa County. Liquefaction is a natural phenomenon in which saturated, sandy soils lose their strength and behave as liquid. Liquefaction is a caused by severe ground shaking during earthquake events. This data set identifies the liquefaction potential for soil in Napa County.
USGS Credits:
Geology by Robert C. Witter, Keith L. Knudsen, Janet M. Sowers, Carl M. Wentworth, Richard D. Koehler, and Carolyn E. Randolph. Digital database by Carl M. Wentworth, Suzanna K. Brooks, and Kathleen D. Gans
County Layer:
County GIS Staff
Spatial Reference: 102642 (2226)
Initial Extent:
XMin: 6165565.46157218
YMin: 1891077.35362532
XMax: 6756815.9144469
YMax: 2026264.30613158
Spatial Reference: 102642 (2226)
Full Extent:
XMin: 6376369.60625
YMin: 1817557.121875
XMax: 6544553.48999999
YMax: 2077327.7175
Spatial Reference: 102642 (2226)
Units: esriFeet
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