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Open-File Report 2008-1246

High-Resolution Chirp and Mini-Sparker Seismic-Reflection Data From the Southern California Continental Shelf—Gaviota to Mugu Canyon

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Frequently-anticipated questions

What does this data set describe?

Title:
High-Resolution Chirp and Mini-Sparker Seismic-Reflection Data From the Southern California Continental Shelf--Gaviota to Mugu Canyon
Abstract:
This report consists of high-resolution chirp and single-channel Sparker seismic-reflection- profile data from the Santa Barbara Channel, California. These data were acquired in 2007 using the Research Vessel Zephyr2 (USGS Cruise ID: Z-3-07-SC) and the Research Vessel Parke Snavely (USGS Cruise ID: S-7-08-SC). The data are available in binary, TIFF and JPEG image formats. Binary data are in Society of Exploration Geologists (SEG) SEG-Y format and may be downloaded for further processing or display. Reference maps and JPEG images of the profiles may be viewed with your Web browser.

Supplemental_Information:
Chirp seismic-reflection profiles are acquired by means of an acoustic source and a hydrophone array, both contained in a single unit towed in the water behind a survey vessel approximately 4 meters below the water surface. The sound source emits a short (30 ms) swept-frequency (500 to 7,200 Hz) acoustic pulse, which propagates through the water and sediment columns. The acoustic energy is reflected at density boundaries (such as the sea floor or sediment layers beneath the sea floor), and detected by the hydrophone array, and digitally recorded by the onboard PC-based acquisition system. As the vessel moves, this process is repeated multiple times per second, producing a two-dimensional image of the shallow geologic structure beneath the ship track. Mini-sparker profiles are collected with a 500 Joule sparker source and 15-m single-channel streamer towed at the sea surface and using the same acquisition system.

Additional information about the USGS survey Z-3-07-SC is available at <http://walrus.wr.usgs.gov/infobank/z/z307sc/html/z-3-07-sc.meta.html>.

Additional information about the USGS survey S-7-08-SC is available at <http://walrus.wr.usgs.gov/infobank/s/s708sc/html/s-7-08-sc.meta.html>.

  1. How should this data set be cited?

    Ray W. Sliter, Peter J. Triezenberg, Patrick E. Hart, 2008, High-Resolution Chirp and Mini-Sparker Seismic-reflection Data From the Southern California Continental Shelf--Gaviota to Mugu Canyon: U.S. Geological Survey Open-File Report 2008-1246, U.S. Geological Survey, Menlo Park, Calif.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -120.2113
    East_Bounding_Coordinate: -119.0521
    North_Bounding_Coordinate: 34.4701
    South_Bounding_Coordinate: 34.0161

  3. What does it look like?

    <https://pubs.usgs.gov/of/2008/1246/data/jpg/HC-01.jpg> (JPEG)
    Example of single-channel chirp seismic data accessible via this report.
    <https://pubs.usgs.gov/of/2008/1246/data/tif/HC-01.tif> (TIFF)
    Example of single-channel chirp seismic data accessible via this report.

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

    Beginning_Date: 12-Sep-2007
    Ending_Date: 01-Jul-2008
    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: 11
      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?

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, Peter J. Triezenberg, Patrick E. Hart, Amy E. Draut, William R. Normark, and James E. Conrad

  2. Who also contributed to the data set?

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

    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
    c/o Ray W. Sliter
    Geophysicist
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5194 (voice)
    (650) 329-5190 (FAX)
    rsliter@usgs.gov

Why was the data set created?

Marine seismic reflection data are used to image and map sedimentary and structural features of the seafloor and subsurface. These data were acquired across the northern shelf area of the Santa Barbara Channel, CA, as part of a multi agency effort to characterize the geologic framework and sedimentary environment of the region. The specific objective of this seismic survey is to provide seismic reflection images of the depositional geometry of the upper 50 meters of subbottom stratigraphy in order to better understand the mechanisms of sediment transport and deposition. These seismic profiles provide high-quality images with approximately 20 cm of vertical resolution and up to 80 m of subbottom penetration.

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: 2008 (process 1 of 7)
    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: 2008 (process 2 of 7)
    Created bathymetry overlay using GMT <http://gmt.soest.hawaii.edu/> Peter J. Triezenberg

    Date: 2008 (process 3 of 7)
    Created interactive trackline map using Google Maps API <http://code.google.com/apis/maps/> Peter J. Triezenberg

    Date: 2008 (process 4 of 7)
    Created downloadable Google Earth "kmz" file <http://code.google.com/apis/kml/> Peter J. Triezenberg

    Date: 2008 (process 5 of 7)
    Created seismic profile images using Seismic Unix <http://www.cwp.mines.edu/cwpcodes/> to provide format options for downloading data. Ray W. Sliter

    Date: 2008 (process 6 of 7)
    Converted profiles to TIFF and JPEG files using ImageMagick <http://www.imagemagick.org/> Peter J. Triezenberg

    Person who carried out this activity:

    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
    c/o Ray W. Sliter
    Geophysicist
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5194 (voice)
    (650) 329-5190 (FAX)
    rsliter@usgs.gov

    Date: 2008 (process 7 of 7)
    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)
    c/o Peter J. Triezenberg
    Geologist
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5207 (voice)
    (650) 329-5190 (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), 2008, USGS CMG Z-3-07-SC Metadata.

    Online Links:

    Other_Citation_Details: Updated daily
    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG), 2008, USGS CMG Z-7-08-SC Metadata.

    Online Links:

    Other_Citation_Details: Updated daily

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:
Physical materials are under controlled on-site access.

If available, access to physical samples is described in the "WR CMG Sample Distribution Policy" at: <http://walrus.wr.usgs.gov/infobank/programs/html/main/sample-dist-policy.html>

Use_Constraints:
Please recognize the U.S. Geological Survey (USGS) as the source of this information.

Physical materials are under controlled on-site access.

Some USGS information accessed through this means may be preliminary in nature and presented without the approval of the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the responsibility of the user.

This information is not intended for navigational purposes.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  1. Who distributes the data set? (Distributor 1 of 1)

    U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
    c/o Ray W. Sliter
    Geophysicist
    USGS, MailStop 999, 345 Middlefield Road
    Menlo Park, CA 94025-3561
    USA

    (650) 329-5194 (voice)
    (650) 329-5190 (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 2008-1246

  3. What legal disclaimers am I supposed to read?

    Please recognize the U.S. Geological Survey (USGS) as the source of this information.

    Physical materials are under controlled on-site access.

    Some USGS information accessed through this means may be preliminary in nature and presented without the approval of the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the responsibility of the user.

    This information is not intended for navigational purposes.

    Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

    • Availability in digital form:

      Data format: SEG-Y, JPEG, TIFF, ASCII Size: 2.5 gigabytes
      Network links: <https://pubs.usgs.gov/of/2008/1246/>
      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: 24-Jul-2008
Metadata author:
U.S. Geological Survey (USGS), Coastal and Marine Geology (CMG)
c/o Ray W. Sliter
Geophysicist
USGS, MailStop 999, 345 Middlefield Road
Menlo Park, CA 94025-3561
USA

(650) 329-5194 (voice)
(650) 329-5190 (FAX)
rsliter@usgs.gov

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

For more information contact: Ray Sliter

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Page Last Modified: 29 July 2008 (mfd)