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| Value | Definition |
|---|---|
| af | Artificial fill. Material constructed or deposited by humans. |
| Qhr | Estuarine deposits (bay mud) |
| Qhr/af | Estuarine deposits with areas of artificial fill |
| Qhi | Latest Holocene alluvial deposits |
| Qhi/Qhb | Latest Holocene flood plain and basin deposits along Laguna de Santa Rosa |
| Qhs | Holocene dune and beach sand |
| Qhb | Holocene basin deposits |
| Qht | Holocene terrace deposits |
| Qhf | Holocene fan deposits |
| Qha | Holocene alluvium, undifferentiated |
| Qs | Late Pleistocene to Holocene dune sands |
| Qt | Late Pleistocene to Holocene terrace deposits |
| Qf | Late Pleistocene to Holocene fan deposits |
| Qa | Late Pleistocene to Holocene alluvium, undifferentiated |
| Qpt | Late Pleistocene terrace deposits |
| Qpf | Late Pleistocene fan deposits |
| Qpa | Late Pleistocene alluvium, undifferentiated |
| Qpm | Late Pleistocene marine terrace deposits |
| Qoa | Early or middle Pleistocene fan or terrace deposits |
| Qom | Early to middle Pleistocene marine terrace deposits |
| br | Pre-Quaternary deposits and bedrock, undifferentiated |
| w | Water |
| Value | Definition |
|---|---|
| H | High susceptibility |
| L | Low susceptibility |
| L-H | low to high susceptibility |
| L-M | Low to Moderate susceptibility |
| M | Moderate susceptibility |
| M-H | Moderate to High susceptibility |
| VH | Very High susceptibility |
| VL | Very Low Susceptibility |
| w | water (not susceptible) |
| Value | Definition |
|---|---|
| contact, certain | Observed contact |
| map boundary, certain | Extent of mapped area |
| water boundary, certain | Body of water boundary |
| Value | Definition |
|---|---|
| Ground cracks | Ground cracks were created during event |
| Lateral spreading | Deposits spread laterally during event |
| ground settlement | Ground settled during event |
| sand boil | Sand boil was created during event |
| Absence of cracks | No cracks were created during event |
| Miscellaneous effects | Not categorized effects of event |
We thank the various people and agencies who provided access to borehole logs and other information on local geology. These include the California Department of Transportation, Wayne Wirick of the City of Sonoma, Sue Kelley of the City of Sebastopol, Roland Brust and Joe Gaffney of the City of Rohnert Park, Maurice Magsamem of the City of Santa Rosa, Janette Alm of CH2MHill, Anthony Quicho of the City of Martinez, Albert Hurd of the City of Fairfield, Gilbert Yau of the City of Vallejo, and Don Cardwell of the City of Napa.
Assistance in field work and map compilation was provided by Jeff Unruh, Meg Schram, Steve Thompson, Tina Wickens, Raymond Huang, and Colleen Haraden of William Lettis & Associates, Inc. We thank Edward Helley for assistance in obtaining reports, maps, and photography of the study area, and John Tinsley and Chuck Real for helpful discussions. Earl Brabb provided guidance during the review process and made the USGS publication of this map possible. John Tinsley and Edward Helley reviewed the manuscript.
This research was supported by the U. S. Geological Survey (USGS), Department of the Interior, under USGS award number 14-08-0001-G2129. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U. S. Government.
Earthquake-induced ground failures such as liquefaction have historically brought loss of life and damage to property and infrastructure. Observations of the effects of historical large-magnitude earthquakes show that the distribution of liquefaction phenomena is not random. Liquefaction is restricted to areas underlain by loose, cohesionless sands and silts that are saturated with water. These areas can be delineated on the basis of thorough geologic, geomorphic, and hydrologic mapping and map analysis. Once potential liquefaction zones are delineated, appropriate public and private agencies can prepare for and mitigate seismic hazard in these zones. In this study, we create a liquefaction susceptibility map of the Napa 1:100,000 quadrangle using Quaternary geologic mapping, analysis of historical liquefaction information, groundwater data, and data from other studies.
Are there legal restrictions on access or use of the data?Access_Constraints: none
Use_Constraints: none
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.
This database, identified as "Quaternary Geology and Liquefaction Susceptibility, Napa, California 1:100,000 Quadrangle: A digital database," has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
| Data format: |
ARC/INFO export file Description of coverage na-geol.e00 Depositional contacts, unit labels, and liquefaction susceptibility na-hist.e00 Historical liquefaction events na-index.e00 Topographic contours base map (from 1:100,000 scale originals) na-drain.e00 Drainage base map (from 1:100,000 scale originals) na-cult.e00 Cultural and map boundary base mapin format ARCE (version 7.x) Size: 14.8 |
|---|---|
| Network links: |
http://pubs.usgs.gov/of/1998/of98-460/na_data.tar.gz |