Folds--Offshore of San Francisco Map Area, California

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Frequently anticipated questions:

What does this data set describe?

Title: Folds--Offshore of San Francisco Map Area, California
Abstract:
This part of DS 781 presents data for folds for the geologic and geomorphic map of the Offshore of San Francisco map area, California. The vector data file is included in "Folds_OffshoreSanFrancisco.zip," which is accessible from <https://pubs.usgs.gov/ds/781/OffshoreSanFrancisco/data_catalog_OffshoreSanFrancisco.html>.
The Offshore of San Francisco map area straddles the right-lateral transform boundary between the North American and Pacific plates and is cut by several active faults that cumulatively form a distributed shear zone, including the San Andreas Fault, the eastern strand of the San Gregorio Fault, the Golden Gate Fault, and the Potato Patch Fault (Bruns and others, 2002; Ryan and others, 2008). These faults are covered by Holocene sediments (mostly units Qms, Qmsb, Qmst) with no seafloor expression, and are mapped using seismic-reflection data. The San Andreas Fault is the primary plate-boundary structure and extends northwest across the map area; it intersects the shoreline 10 km north of the map area at Bolinas Lagoon, and 3 km south of the map area at Mussel Rock. This section of the San Andreas Fault has an estimated slip rate of 17 to 24 mm/yr (U.S. Geological Survey, 2010), and the devastating Great 1906 California earthquake (M 7.8) is thought to have nucleated on the San Andreas a few kilometers offshore of San Francisco within the map area (Bolt, 1968; Lomax, 2005).

The San Andreas Fault forms the boundary between two distinct basement terranes, Upper Jurassic to Lower Cretaceous rocks of the Franciscan Complex to the east, and Late Cretaceous granitic and older metamorphic rocks of the Salinian block to the west. Franciscan Complex rocks (unit KJf, undivided) form seafloor outcrops at and north of Point Lobos adjacent to onland exposures. The Franciscan is divided into 13 different units for the onshore portion of this geologic map based on different lithologies and ages, but the unit cannot be similarly divided in the offshore because of a lack of direct observation and (or) sampling.

Folds were primarily mapped by interpretation of seismic reflection profile data (see field activities S-15-10-NC and F-2-07-NC). The seismic reflection profiles were collected between 2007 and 2010.

References Cited

Bolt, B.A., 1968, The focus of the 1906 California earthquake: Bulletin of the Seismological Society of America, v. 58, p. 457-471.

Bruns, T.R., Cooper, A.K., Carlson, P.R., and McCulloch, D.S., 2002, Structure of the submerged San Andreas and San Gregorio fault zones in the Gulf of Farallones as inferred from high-resolution seismic-reflection data, in Parsons, T. (ed.), Crustal structure of the coastal and marine San Francisco Bay region, California: U.S. Geological Survey Professional Paper 1658, p. 77-117.

Lomax, A., 2005, A reanalysis of the hypocentral location and related observations for the Great 1906 California earthquake: Bulletin of the Seismological Society of America, v. 95, p. 861-877.

Ryan, H.F., Parsons, T., and Sliter, R.W., 2008. Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California. Tectonophysics, 429 (1-2), p. 209-224.

U.S. Geological Survey and California Geological Survey, 2010, Quaternary fault and fold database for the United States, accessed April 5, 2012, from USGS website: <http://earthquake.usgs.gov/hazards/qfaults/>.

Supplemental_Information:
Map political location: San Mateo County, California Compilation scale: 1:24,000 Base maps used are hillshades generated from IfSAR, LiDAR, and multibeam mapping both onshore and offshore (see Bathymetry Hillshade--Offshore San Francisco, California, DS 781, for more information).
  1. How should this data set be cited?

    Greene, H.G., Johnson, S.Y., Manson, M.W., Hartwell, S.R., Endris, C.A., and Bruns, T.R., 2014, Folds--Offshore of San Francisco Map Area, California:.

    This is part of the following larger work.

    Cochrane, Guy R., Johnson, Samuel Y., Dartnell, Peter, Greene, H. Gary, Erdey, Mercedes D., Golden, Nadine E., Hartwell, Stephen R., Endris, Charles A., Mansion, Michael W., Sliter, Ray W., Kvitek, Rikk G., Watt, Janet T., Ross, Stephanie L., and Bruns, Terry R., 2015, California State Waters Map Series--Offshore of San Francisco Map Area, California: Open-File Report OFR 2015-1068, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -122.55
    East_Bounding_Coordinate: -122.51
    North_Bounding_Coordinate: 37.74
    South_Bounding_Coordinate: 37.70

  3. What does it look like?

    <https://pubs.usgs.gov/ds/781/OffshoreSanFrancisco/images/Folds_OffshoreSanFrancisco.jpg> (JPEG)
    Folds offshore San Francisco.

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 2007
    Ending_Date: 2010
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  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):

      • String (4)

    2. What coordinate system is used to represent geographic features?

      The map projection used is WGS 1984 UTM Zone 10N.

      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.0001
      Ordinates (y-coordinates) are specified to the nearest 0.0001
      Planar coordinates are specified in Meter

      The horizontal datum used is D WGS 1984.
      The ellipsoid used is WGS 1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.

  7. How does the data set describe geographic features?

    Folds
    lines representing mapped folds (Source: This report)

    OBJECTID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    Label
    feature label (Source: this report)

    text field containing feature names if they are named

    RuleID
    Representation rule identifier (Source: This report)

    This field contains the representation rule in the ArcGIS file geodatabase that applied dashed or solid lines to folds. The line is dashed if folds are mapped in sediment and solid if they are mapped over rock or a visible scarp.

    Shape_Length
    Length of feature in internal units. (Source: ESRI)

    Positive real numbers that are automatically generated.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    USGS Pacific Coastal and Marine Science Center
    Attn: Stephen Hartwell
    Geologist
    400 Natural Bridges Drive
    Santa Cruz, CA 95060
    USA

    (831) 460-7814 (voice)
    (831) 427-4748 (FAX)
    shartwell@usgs.gov

Why was the data set created?

To expand geologic mapping to the seafloor within the California's State Waters, to update coastal geologic mapping, and to contribute to a uniform regional geologic database, which can be used geographic information systems. Additionally, to provide a geologic map for the public and geoscience community to aid in assessments and mitigation of geologic hazards in the San Gregorio coastal region and to provide sufficient geologic information for land-use and land-management decisions both onshore and offshore. This information is not intended for navigational purposes.

How was the data set created?

  1. From what previous works were the data drawn?

    S-15-10-NC (source 1 of 2)
    U.S. Geological Survey (USGS) , Coastal and Marine Geology Program (CMGP), 2013, Seismic-reflection data acquisition data of field activity S-15-10-NC in offshore Pescadero from 08/02/2010 to 08/04/2010: U.S. Geological Survey (USGS) , Coastal and Marine Geology (CMG), Menlo Park, CA.

    Online Links:

    Type_of_Source_Media: ASCII lat/long shot point files
    Source_Contribution:
    Digital seismic data used to interpret subsurface geologic structure

    F-2-07-NC (source 2 of 2)
    U.S. Geological Survey (USGS), Coastal and Marine Geology Program (CMGP), 2013, Geophysical data of field activity F-2-07-NC in Ano Nuevo to San Francisco from 03/22/2007 to 04/06/2007: U.S. Geological Survey (USGS) , Coastal and Marine Geology (CMG), Menlo Park, CA.

    Online Links:

    Type_of_Source_Media: ASCII lat/long shot point files
    Source_Contribution:
    Digital seismic data used to interpret subsurface geologic structure

  2. How were the data generated, processed, and modified?

    Date: 2010 (process 1 of 2)
    Folds were mapped onto shot lines based on the latitude and longitude of seismic picks from field activity S-15-10-NC.

    Date: 2011 (process 2 of 2)
    Folds were mapped onto shot lines based on the latitude and longitude of seismic picks from field activity F-2-07-NC.

  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?

    Folds were primarily mapped by interpretation of seismic reflection profile data (see field activities S-15-10-NC and F-2-07-NC).
    Folds lines were digitized by heads-up screen digitization on to shot point picks from seismic line navigation data - each shot point has an associated lat/long in the survey data. Error is introduced from layback, as well as from interpretation of oblique features, so horizontal accuracy of fault and fold location is estimated to be on the order of 10 to 20 meters.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Data are complete: no offshore features that could be accurately identified and represented at the compilation scale of 1:24,000 were eliminated or generalized. The smallest area represented is approximately 100 square meters. All geospatial database elements are attributed.

  5. How consistent are the relationships among the observations, including topology?

    Map elements were visually checked for overshoots, undershoots, duplicate features, and other errors by the lead authors and by the GIS technician(s) who created the digital database. Review drafts of the map were reviewed internally by at least two other geologists for consistency with basic geologic principles and general conformity to USGS mapping standards.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:
If physical samples or materials are available, constraints on their on-site access are described in "WR CMG Sample Distribution Policy" at URL: <http://walrus.wr.usgs.gov/infobank/programs/html/main/sample-dist-policy.html>
Use_Constraints:
This information is not intended for navigational purposes.
Read and fully comprehend the metadata prior to data use. Uses of these data should not violate the spatial resolution of the data. Where these data are used in combination with other data of different resolution, the resolution of the combined output will be limited by the lowest resolution of all the data.
Acknowledge the U.S. Geological Survey in products derived from these data. Share data products developed using these data with the U.S. Geological Survey.
This 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.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document these data in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.

Who wrote the metadata?

Dates:
Last modified: 2013
Last Reviewed: 02-Sep-2014
Metadata author:
U.S. Geological Survey, Coastal and Marine Geology Program
Attn: Stephen R. Hartwell
400 Natural Bridges Drive
Santa Cruz, CA 95060-5792
US

831-460-7814 (voice)
831-427-4748 (FAX)
shartwell@usgs.gov

Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

Generated by mp version 2.9.16 on Mon May 18 16:05:14 2015