Sub-bottom chirp data acquired in the Salton Sea, California, between 2006 and 2008

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Frequently anticipated questions:

What does this data set describe?

Sub-bottom chirp data acquired in the Salton Sea, California, between 2006 and 2008
More than 1,000 line-km of sub-bottom chirp data were collected with an Edgetech 0.5-16 kHz subscan system by Scripps Institution of Oceanography between 2006 and 2008 in the Salton Sea, California, with assistance from the U.S. Geological Survey (USGS). Data were subsequently donated by Scripps to the USGS for public release (USGS field activity identifier 2006-603-DD).
Additional information about the field activity from which these data were derived is available online at:
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.
  1. How might this data set be cited?
    Brothers, Daniel S., Driscoll, Neal W., Kent, Graham M., Baskin, Robert L., and Balster-Gee, Alicia F., 20220322, Sub-bottom chirp data acquired in the Salton Sea, California, between 2006 and 2008: data release DOI:10.5066/P9ER5TNT, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -116.13977054
    East_Bounding_Coordinate: -115.55090312
    North_Bounding_Coordinate: 33.57526889
    South_Bounding_Coordinate: 33.06484469
  3. What does it look like?
    SaltonSeaChirp_Map_2006-603-DD.png (PNG)
    Map of chirp tracklines collected between 2006 and 2008
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 04-Aug-2006
    Ending_Date: 04-Sep-2008
    Ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: seismic-reflection data in SEG-Y format
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Horizontal X and Y locations for the seismic profile locations are provided and stored in the SEG-Y data trace headers in header bytes 81 and 85 locations.
    2. What coordinate system is used to represent geographic features?
      The map projection used is WGS 1984 UTM Zone 11N.
      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -117.0
      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.
      Depth_Datum_Name: Local surface
      Depth_Resolution: 0.1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    Navigation and seismic shots with Time Stamp in standard SEG-Y file format
    Society of Exploration Geophysicists (SEG) Technical Standards, available for download at

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Daniel S. Brothers
    • Neal W. Driscoll
    • Graham M. Kent
    • Robert L. Baskin
    • Alicia F. Balster-Gee
  2. Who also contributed to the data set?
    California Department of Water Resources, California Department of Fish and Game, UCSD Academic Senate, Scripps Institution of Oceanography, Sonny Bono Salton Sea National Wildlife Refuge, National Science Foundation, and Southern California Earthquake Center
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)

Why was the data set created?

The Salton Sea is a large, shallow lake located in the central Salton Trough of Southern California that covers the southernmost extension of the San Andreas Fault (SAF) and the northernmost transtensional step-over associated with Gulf of California oblique rifting. Seismic hazard assessments require regional studies that account for rupture along secondary faults and their potential to inhibit or promote failure on the SAF. Therefore, understanding the kinematic relationships and seismic cycling between the SAF and extensional faults beneath the Salton Sea is of utmost importance. The data in this report were acquired to better understand the late-Holocene depositional framework and deformation history within the submerged portion of the San Andreas-Imperial Fault pull-apart basin, and to examine coseismic deformation preserved in Lake Cahuilla sediments. Previously published articles (for example, Brothers and others, 2009; Brothers and others, 2011) used the sub-bottom chirp data included in this release to map numerous faults, to define the shallow basin architecture, and to estimate the timing of coseismic displacement across several faults. The Scripps Institution of Oceanography was the lead institution for this field activity; the data have been donated for public release. These data and information are intended for science researchers, students from elementary through college, policy makers, and the general public.

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: 04-Sep-2008 (process 1 of 2)
    The chirp seismic-reflection profiles were acquired with a swept-frequency source towed at about 3 meters below the sea surface. Data were recorded to Edgetech JSF format using Edgetech recording software. Survey speeds were approximately 4 knots. Sub-bottom surveys employed different chirp pulses depending on sub-bottom conditions. The 0.7 – 3.0 kHz, 50 ms pulse provided greatest penetration (up to 60 m) while the 1.0 – 15.0 kHz, 30 ms pulse produced the highest vertical resolution (~15 cm). Acquisition parameters for all SEG-Y files are recorded in the textual headers.
    Date: 25-May-2022 (process 2 of 2)
    Correction was made to keywords. No data were changed. (
  3. What similar or related data should the user be aware of?
    Brothers, Daniel S., Driscoll, Neal W., Kent, Graham M., Harding, A. J., Babcock, J. M., and Baskin, Robert L., 2009, Tectonic evolution of the Salton Sea inferred from seismic reflection data.

    Online Links:

    Brothers, D., Driscoll, N., Kent, G., Harding, A.J., Babcock, J.M., and Baskin, R.L., 2009, Tectonic evolution of the Salton Sea inferred from seismic reflection data: Nature Geoscience, v. 2, p. 581–584,
    Brothers, Daniel S., Klib, D. K., Luttrell, K., Kent, Graham M., Lin, G., and Driscoll, Neal W., 2011, Loading of the San Andreas fault by flood-induced rupture of faults beneath the Salton Sea.

    Online Links:

    Brothers, D., Kilb, D., Luttrell, K., Driscol, N., and Graham, K., 2011, Loading of the San Andreas fault by flood-induced rupture of faults beneath the Salton Sea: Nature Geoscience, v. 4, p. 486–492,

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

  1. How well have the observations been checked?
    Identified as the best available version.
  2. How accurate are the geographic locations?
    Position data were provided by a Hemisphere V100 Global Positioning System using L1, C/A code and carrier phase smoothing with a stated accuracy of 60 centimeters.
  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?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    Subbottom data were collected between 2006 and 2008 by researchers from Scripps Institution of Oceanography aboard USGS Utah Water Science Center’s R/V Stevens using a custom Edgetech sub-bottom profiling system owned by the Scripps Institution of Oceanography. This system consists of a source transducer and an array of receiving hydrophones housed in a 500-lb “fish” towed at a depth of several meters below the water surface. The swept-frequency “chirp” source signal is between 500 and 16,000 Hz, and data are recorded by hydrophones located on the bottom of the fish. Quality control was conducted during the collection process.

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 USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey and Scripps Institution of Oceanography as the originators of the dataset and in products derived from these data. This information is not intended for navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - CMGDS
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
  2. What's the catalog number I need to order this data set? contains high-resolution seismic-reflection (SEG-Y) data donated to PCMSC for public release by Scripps Institution of Oceanography. These data are divided up and presented by navigation line, as reflected in the individual file names.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata, and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: Zip file contains the raw seismic data per navigation line in format SEG-Y (version SEG-Y rev 1) Size: 21500
      Network links:
    • 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; VISTA by Seismic Image Software; SeiSee by Dalmorneftegeophysica (DMNG); amongst others.

Who wrote the metadata?

Last modified: 25-May-2022
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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