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Open-File Report 2016-1058

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High-Resolution Seismic-Reflection Data from Offshore of Northern California—Bolinas to Sea Ranch

Frequently-anticipated Questions

Metadata also available as - [Outline] - [Parseable text] - [XML]

Frequently anticipated questions:

What does this data set describe?

Title:
High-Resolution Seismic-Reflection Data from Offshore of Northern CaliforniaÑBolinas to Sea Ranch
Abstract:
The U.S. Geological Survey collected high-resolution seismic-reflection data in September 2009, on survey S-8-09-NC, offshore of northern California between Bolinas and Sea Ranch.

The survey area spans about 125 km of California's coast and extends around Point Reyes. Data were collected aboard the U.S. Geological Survey R/V Parke Snavely. Cumulatively, ~1,150 km of seismic-reflection data were acquired using a SIG 2mille minisparker. Subbottom acoustic depth of penetration spanned tens to several hundred meters and varied by location and underlying sediments and rock types.

This report includes maps and a navigation file of the surveyed transects, utilizing Google Earthª software, as well as digital data files showing images of each transect in SEG-Y and JPEG formats. The images of bedrock, sediment deposits, and tectonic structure provide geologic information that is essential to hazard assessment, regional sediment management, and coastal and marine spatial planning at Federal, State and local levels. This information is also valuable for future research on the geomorphic, sedimentary, tectonic, and climatic record of central California.

Supplemental_Information:
Data were acquired on cruise S-08-09-NC in September, 2009. Information on this cruise is available at http://cmgds.marine.usgs.gov/fan_info.php?fan=S809NC. Using a SIG 2mille minisparker source, ~1,150 km of seismic-reflection profiles were collected at ~1,000-m line spacing.

The SIG 2mille minisparker system uses a 500-Joule, high-voltage electrical discharge that was fired at intervals ranging from 0.50Ð0.75 seconds depending on water depth. The source signal frequency bandwidth ranges from 200Ð1600 Hz. Half-second intervals were used where water depth was less than 350 m, which characterizes most of the study area. The 0.50-second firing rate and normal survey speeds of 4Ð4.5 nautical miles per hour yield a data trace about every meter. The data were recorded on a 15-m-long hydrophone streamer in standard SEG-Y 32-bit floating-point format, using Triton Subbottom Logger (SBL) software that merges seismic-reflection data with differential global positioning system (GPS) navigation data. After the survey, ship-heave statics were calculated using SIOSEIS seismic processing software, and these corrections were applied to the data to filter out the effect of the sea swell. A short-window (20 ms) automatic gain control algorithm and a 160Ð1,200-Hz bandpass filter was applied to the minisparker data. Data quality varies with substrate, with penetration ranging up to as much as 200Ð300 m in inferred fine-grained sediments.

  1. How might this data set be cited?
    Ray W. Sliter, Samuel Y. Johnson, John L. Chin, Parker Allwardt, Jeffrey Beeson, and Peter J. Triezenberg, 2016, High-Resolution Seismic-Reflection Data from Offshore of Northern CaliforniaÑBolinas to Sea Ranch: U.S. Geological Survey Open-File Report 2016Ð1058, U.S. Geological Survey, Menlo Park, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -123.5205
    East_Bounding_Coordinate: -122.3089
    North_Bounding_Coordinate: 38.7091
    South_Bounding_Coordinate: 37.5906
  3. What does it look like?
    <https://pubs.usgs.gov/of/2016/1058/tracklines/jpg/PR-07.jpg> (JPEG)
    Example of single-channel mini-sparker seismic data accessible via this report.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 08-Sep-2009
    Ending_Date: 30-Sep-2009
    Currentness_Reference: ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: seismic reflection profile section
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference:
      Horizontal X and Y locations for the seimic profiles location are provided in ASCII position files and are also stored in the SEG-Y data trace headers in the standard header locations.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 10
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -119.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 3
      Ordinates (y-coordinates) are specified to the nearest 3
      Planar coordinates are specified in seconds
      The horizontal datum used is World Geodetic System 1984.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    Ascii data set s-8-09-nc.410_sparker has initial header records followed by data records with these fields - 4-digit year, 3-digit day of year, 2-digit hour, 2-digit minute, 2-digit second, 1-digit tenth of second, decimal degree latitude, decimal degree longitude, alpha-numeric line ID, FFID number, Shot number, and CDP number. Example: 
    					! 10/16/2009 ray s-8-09-nc.410_sparker
					! /infobank/programs/edit/mergeit/mergeit
					! merged SEG-Y shots with s-8-09-nc.061 Ray Sliter 10/26/09
					!
					20092521622440  38.01074 -122.89369        PR-01         1         1         1
					20092521622500  38.01067 -122.89376        PR-01         2         2         2
					20092521622510  38.01066 -122.89378        PR-01         4         4         4
					20092521622520  38.01064 -122.89379        PR-01         6         6         6
					20092521622530  38.01063 -122.89380        PR-01         8         8         8
    Entity_and_Attribute_Detail_Citation:
    U.S. Geological Survey, USGS CMG InfoBank format for Seismic FFID/Shot/CDP data, 2012, <http://walrus.wr.usgs.gov/infobank/programs/html/dictionary2html/format_410.html>.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Ray W. Sliter, Samuel Y. Johnson, John L. Chin, Parker Allwardt, Jeffrey Beeson, and Peter J. Triezenberg
  2. Who also contributed to the data set?
    U.S. Geological Survey
  3. To whom should users address questions about the data?
    U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC)
    Attn: Ray W. Sliter
    Geophysicist
    USGS, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7427 (voice)
    (831) 460-7456 (FAX)
    rsliter@usgs.gov

Why was the data set created?

In September 2009, the U.S. Geological Survey (USGS) collected high-resolution seismic-reflection data offshore of northern California between Bolinas and Sea Ranch (fig. 1). The survey area spans ~125 km of the coastline, extending offshore beyond the 3-nautical-mile limit of California's State Waters. The southern part of the survey area stretches around the Point Reyes National Seashore and extends in to the Gulf of the Farallones National Marine Sanctuary. Data were collected aboard the USGS R/V Parke Snavely. Cumulatively, ~1,150 km of seismic-reflection lines were acquired.

The study area is cut by the northern San Andreas Fault (Clark and Brabb, 1997; Prentice and Kelson, 2006), which is the primary structure in the widely distributed transform plate boundary along much of the west coast of North America (for example, Argus and Gordon, 2001). In this area, the San Andreas Fault lies offshore between Bodega Bay and Tomales Bay, and between Salmon Creek and Fort Ross. Outside of these areas, the onshore fault zone forms a prominent topographic lineament that coincides with Bolinas Lagoon and Tomales Bay. This section of the San Andreas Fault has an estimated slip rate of 17Ð24 mm per year (U.S. Geological Survey, 2010). The devastating Great 1906 California earthquake (M 7.8) is thought to have nucleated on the San Andreas Fault a few kilometers south of this survey area, offshore of San Francisco (for example, Bolt, 1968; Lomax, 2005).

The study area has particular interest for environmental and geologic hazards considerations. Understanding the regionÕs ecosystems and how they function is fundamental to effective stewardship of California's State Waters, the National Seashore, and the National Marine Sanctuary. The need for accurate characterization of the seafloor and its substrate, including sediment distribution and thickness, as revealed by high-resolution seismic-reflection data, is important for building such an understanding.

Finally, these geophysical data will contribute to a range of geologic and habitat map products that will be used for a variety of coastal and marine spatial-planning applications.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2012 (process 1 of 8)
    Refer to report sections "Data Acquisition and Processing" for details of geophysical data acquisition and processing sequence used for data in this report. - Ray W. Sliter
    Date: 2012 (process 2 of 8)
    Created bathymetry overlay using GMT <http://gmt.soest.hawaii.edu/>. - Peter J. Triezenberg
    Date: 2012 (process 3 of 8)
    Created interactive trackline map using Google Maps API <http://code.google.com/apis/maps/>. - Peter J. Triezenberg
    Date: 2012 (process 4 of 8)
    Created downloadable Google Earth "kmz" file <http://code.google.com/apis/kml/>. - Peter J. Triezenberg
    Date: 2012 (process 5 of 8)
    Calculated and applied seismic heave statics using SIOSEIS <http://sioseis.ucsd.edu/> - Jeff Beeson
    Date: 2012 (process 6 of 8)
    Created seismic profile images using Seismic Unix <http://www.cwp.mines.edu/cwpcodes/> to provide format options for downloading data. - Ray W. Sliter Person who carried out this activity:
    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
    Attn: Ray W. Sliter
    Geophysicist
    USGS, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7427 (voice)
    (831) 427-4709 (FAX)
    rsliter@usgs.gov
    Date: 2012 (process 7 of 8)
    Converted profiles to JPEG files using ImageMagick <http://www.imagemagick.org/>. - Ray W. Sliter
    Date: 2012 (process 8 of 8)
    Used GEODAS (GEOphysical DAta System) to create a custom bathymetric and topographic grid for the southern California region covered by the cruise maps. The website is: <http://www.ngdc.noaa.gov/mgg/geodas/geodas.html>. The parameters used are as follows: Grid Database: US Coastal Relief Model Grids Grid Area in degrees and minutes: 34:30 N to 33:48 N, 119:00 W to 120:24 W Grid Cell Size: 3 seconds Grid Format: XYZ (lon, lat, depth), no header, space-delimited, omit empty grid cells. Cell Parameters: 4-byte floating point, tenths of meters Land/Sea Coverage: Sea cells only. - Peter J. Triezenberg Person who carried out this activity:
    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
    Attn: Peter J. Triezenberg
    Geologist
    USGS, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-7413 (voice)
    (831) 427-4709 (FAX)
    ptriezenberg@usgs.gov
  3. What similar or related data should the user be aware of?
    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG), 2013, USGS CMG S-8-09-NC Metadata.

    Online Links:

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

  1. How well have the observations been checked?
    Data have not been independently verified.
  2. How accurate are the geographic locations?
    Shot point numbers in the data files correspond to those in the navigation files. The horizontal positional accuracy of the seismic data thus linked to ship's position is estimated to be within 30 meters.
  3. How accurate are the heights or depths?
    Depths shown in the seismic data files are in milliseconds (round trip travel time) and are referenced to sea level.
  4. Where are the gaps in the data? What is missing?
    Reference the full report for a description of data coverage. All seismic-reflection data collected on the referenced cruises have been included in this report. Some seismic profiles have gaps in them due to system crashes, mammal shutdowns or hardware maintenance.
  5. How consistent are the relationships among the observations, including topology?
    Undetermined

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
Information presented in this publication is considered public information and may be distributed or copied.
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.

  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
    Attn: Ray W. Sliter
    Geophysicist
    USGS, 400 Natural Bridges Drive
    Santa Cruz, CA
    USA

    (831) 460-4727 (voice)
    (831) 427-4709 (FAX)
    rsliter@usgs.gov
    Contact_Instructions:
    Data may be available off-line only by special arrangement with the distributor above. Please use the on-line download option unless precluded by download times or access difficulties.
  2. What's the catalog number I need to order this data set? U.S. Geological Suvey Open-File Report 2013-1071
  3. What legal disclaimers am I supposed to read?
    This information is not intended for navigational purposes.

    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.

    Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.

  4. How can I download or order the data?
    • Availability in digital form:
      Data format: SEG-Y, JPEG, ASCII Size: 2500
      Network links: <https://pubs.usgs.gov/of/2016/1058/>
      Media you can order: none (format ISO 9660)
    • Cost to order the data: None

  5. What hardware or software do I need in order to use the data set?
    Use of SEG-Y data requires specialized software, such as ProMax and Seisworks by Landmark Geophysical; FOCUS and SeisX by Paradigm Geophysical; SPW by Parallel Geoscience; or VISTA by Seismic Image Software.

Who wrote the metadata?

Dates:
Last modified: 12-Jun-2013
Metadata author:
U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
Attn: Ray W. Sliter
Geophysicist
USGS, 400 Natural Bridges Drive
Santa Cruz, CA
USA

(831) 460-7427 (voice)
(831) 427-4709 (FAX)
rsliter@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Generated by mp version 2.9.33 on Thu Jul 14 09:39:21 2016
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