Quaternary geology and liquefaction susceptibility, Napa, California 1:100,000 quadrangle: A digital database

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Frequently anticipated questions:

What does this data set describe?

Quaternary geology and liquefaction susceptibility, Napa, California 1:100,000 quadrangle: A digital database
This Open-File report consists of a digital geologic map database and associated digital plot files and text files, revised from a hard copy by Sowers and others (1995). This digital map database provides current information on Quaternary geology and liquefaction susceptibility of the Napa, California, 1:100,000 quadrangle. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey.
  1. How might this data set be cited?
    Sowers, Janet M., Noller, Jay S., and Lettis, William R., 1998, Quaternary geology and liquefaction susceptibility, Napa, California 1:100,000 quadrangle: A digital database: U.S. Geological Survey Open-File Report 98-460.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -123.0
    East_Bounding_Coordinate: -122.0
    North_Bounding_Coordinate: 38.5
    South_Bounding_Coordinate: 38.0
  3. What does it look like?
    http://pubs.usgs.gov/of/1998/of98-460/na_plate1.pdf (PDF)
    PDF representation of the Quaternary geologic map sheet.
    http://pubs.usgs.gov/of/1998/of98-460/na_plate2.pdf (PDF)
    PDF representation of the liqeuefaction map sheet.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 1998
    publication date of digital map database
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: map
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Entity point
      • Complete chain
      • GT-polygon composed of chains
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 10
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest unknown
      Ordinates (y-coordinates) are specified to the nearest unknown
      Planar coordinates are specified in meters
  7. How does the data set describe geographic features?
    Geologic map units (Source: OFR-98-460)
    Polygon type (Source: OFR-98-460)
    afArtificial fill. Material constructed or deposited by humans.
    QhrEstuarine deposits (bay mud)
    Qhr/afEstuarine deposits with areas of artificial fill
    QhiLatest Holocene alluvial deposits
    Qhi/QhbLatest Holocene flood plain and basin deposits along Laguna de Santa Rosa
    QhsHolocene dune and beach sand
    QhbHolocene basin deposits
    QhtHolocene terrace deposits
    QhfHolocene fan deposits
    QhaHolocene alluvium, undifferentiated
    QsLate Pleistocene to Holocene dune sands
    QtLate Pleistocene to Holocene terrace deposits
    QfLate Pleistocene to Holocene fan deposits
    QaLate Pleistocene to Holocene alluvium, undifferentiated
    QptLate Pleistocene terrace deposits
    QpfLate Pleistocene fan deposits
    QpaLate Pleistocene alluvium, undifferentiated
    QpmLate Pleistocene marine terrace deposits
    QoaEarly or middle Pleistocene fan or terrace deposits
    QomEarly to middle Pleistocene marine terrace deposits
    brPre-Quaternary deposits and bedrock, undifferentiated
    Liquefaction susceptibility (Source: OFR-98-460)
    HHigh susceptibility
    LLow susceptibility
    L-Hlow to high susceptibility
    L-MLow to Moderate susceptibility
    MModerate susceptibility
    M-HModerate to High susceptibility
    VHVery High susceptibility
    VLVery Low Susceptibility
    wwater (not susceptible)
    Linear features on geologic map (Source: OFR-98-460)
    Line type (Source: OFR-98-460)
    contact, certainObserved contact
    map boundary, certainExtent of mapped area
    water boundary, certainBody of water boundary
    Surficial deposits at specific points (same attributes as polygon coverage NA-GEOL.PAT) (Source: OFR-98-460)
    Historical liquefaction events (Source: OFR-98-460)
    probable geologic unit of the historical liquefaction event (same as geologic units of polygon coverage NA-GEOL.PAT) (Source: OFR-98-460)
    Type of event (Source: OFR-98-460)
    Ground cracksGround cracks were created during event
    Lateral spreadingDeposits spread laterally during event
    ground settlementGround settled during event
    sand boilSand boil was created during event
    Absence of cracksNo cracks were created during event
    Miscellaneous effectsNot categorized effects of event

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Janet M. Sowers
    • Jay S. Noller
    • William R. Lettis
  2. Who also contributed to the data set?
    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.
  3. To whom should users address questions about the data?
    Janet M. Sowers
    William Lettis & Associates, Inc.
    Willam Lettis & Associates, Inc., 1777 Botelho Dr., Suite 262
    Walnut Creek, CA

    (925)256-6070 (voice)
    (925)256-6076 (FAX)

Why was the data set created?

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.

How was the data set created?

  1. From what previous works were the data drawn?
    Sowers and others (1995) (source 1 of 1)
    Sowers, J.M., Noller, J.S., and Lettis, W.R., 1995, Maps showing Quaternary geology and liquefaction susceptibility in the Napa, California, 1:100,000 sheet: U.S. Geological Survey Open-File Report OFR-95-205.

    Type_of_Source_Media: paper
    Source_Scale_Denominator: 100,000
    Source_Contribution: The digital map database was revised from this hard copy.
  2. How were the data generated, processed, and modified?
    (process 1 of 2)
    Digital Compilation The geologic map information was digitized from stable original of the geologic map at 1:100,000 scale. The author manuscripts (pencil on mylar) were scanned using a Altek monochrome scanner with a resolution of 800 dots per inch. The scanned images were vectorized and transformed from scanner coordinates to projection coordinates with digital tics placed by hand at map corners. The scanned lines were edited interactively by hand using ALACARTE, color boundaries were tagged as appropriate, and scanning artifacts visible at 1:100,000 were removed.
    Base Maps Base Map layers were prepared from scale-stable printing negatives of the U.S. Geological Survey Napa, California 1:100,000 topographic maps, which have a 50 meter contour interval. Scanned and vectorized images were transformed from scanner coordinates to projection coordinates with digital tics placed by hand at map corners. The images were then trimmed interactively by hand using ALACARTE to conform to the area of the geologic coverages, and the four portions were combined.
    Date: 24-Jul-2000 (process 2 of 2)
    Creation of original metadata record Person who carried out this activity:
    Jennifer Lenz
    US Geological Survey
    12201 Surise Valley Drive, Mail Stop 918
    Reston, VA

    703-648-6974 (voice)
    703-648-6560 (FAX)
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Only surficial deposits. All bedrock is mapped as undifferentiated.
  5. How consistent are the relationships among the observations, including topology?
    This digital map database, compiled from previously published data, and new mapping by the authors, represents the general distribution of surficial deposits in the Napa region.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: none
Use_Constraints: none
  1. Who distributes the data set? (Distributor 1 of 1)
    USGS Information Services
    Box 25286, Denver Federal Center
    Denver, Colorado

    1-888-ASK-USGS (voice)
    1-303-202-4695 (FAX)
  2. What's the catalog number I need to order this data set? USGS Open-File Report 98-460
  3. What legal disclaimers am I supposed to read?
    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.
  4. How can I download or order the data?
    • Availability in digital form:
      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 map
      in format ARCE (version 7.x) Size: 14.8
      Network links: http://pubs.usgs.gov/of/1998/of98-460/na_data.tar.gz
    • Cost to order the data: none

Who wrote the metadata?

Last modified: 05-Feb-2016
Metadata author:
Peter N Schweitzer
USGS Midwest Area
Collection manager, USGS Geoscience Data Clearinghouse, http://geo-nsdi.er.usgs.gov/
Mail Stop 954
12201 Sunrise Valley Dr
Reston, VA

703-648-6533 (voice)
703-648-6252 (FAX)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://geo-nsdi.er.usgs.gov/metadata/open-file/98-460/metadata.faq.html>
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