Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore southern California

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Frequently anticipated questions:

What does this data set describe?

Title:
Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore southern California
Abstract:
Seismic-reflection data were collected offshore southern California in 1972 aboard the USNS Bartlett (USGS Field Activity B-1-72-SC). In 2021 these legacy data were reprocessed to improve accuracy and geologic resolvability of California’s continental margin.
Supplemental_Information:
Additional information about the field activities from which these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=B172SC https://cmgds.marine.usgs.gov/fan_info.php?fan=B272SC https://cmgds.marine.usgs.gov/fan_info.php?fan=B372SC https://cmgds.marine.usgs.gov/fan_info.php?fan=B472SC
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
The effort to rescue and reprocess these legacy seismic-reflection data profiles was supported by Pacific Gas and Electric (PG&E) through a USGS Cooperative Research and Development Agreement (CRADA). Stu Nishenko is thanked for providing copies of the original analog profiles and navigation.
  1. How might this data set be cited?
    Kennedy, Daniel J., Balster-Gee, Alicia F., Sliter, Ray W., and Kluesner, Jared W., 20220428, Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore southern California: data release DOI:10.5066/P9EK7CG3, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Kennedy, Daniel J., Balster-Gee, Alicia F., Sliter, Ray W., and Kluesner, Jared W., 2022, Reprocessed legacy seismic-reflection data from USGS field activity B-1-72-SC collected offshore central and southern California: data release DOI:10.5066/P9EK7CG3, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -120.6839
    East_Bounding_Coordinate: -117.38731
    North_Bounding_Coordinate: 34.2616
    South_Bounding_Coordinate: 32.40505
  3. What does it look like?
    B-1-72-SC_Tracklines_UTM11N.png (PNG)
    Map of seismic-reflection tracklines from B-1-72-SC falling within the UTM zone 11N geographic area of southern California.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 09-Nov-1972
    Ending_Date: 01-Dec-1972
    Currentness_Reference:
    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?
      Indirect_Spatial_Reference:
      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.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      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?
    Entity_and_Attribute_Overview:
    Navigation and seismic shots with Time Stamp in standard SEG-Y file format
    Entity_and_Attribute_Detail_Citation:
    Society of Exploration Geophysicists (SEG) Technical Standards, available for download at http://seg.org/Publications/SEG-Technical-Standards

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Daniel J. Kennedy
    • Alicia F. Balster-Gee
    • Ray W. Sliter
    • Jared W. Kluesner
  2. Who also contributed to the data set?
  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)
    pcmsc_data@usgs.gov

Why was the data set created?

Data were acquired to map geologic structure of central and southern California’s continental margin. The reprocessed dataset increases positional accuracy and enhances the data quality which will be useful for future research on the geomorphic, sedimentary and tectonic record offshore California. These data are intended for science researchers, students, 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: 10-Dec-1972 (process 1 of 4)
    Original seismic-reflection data were acquired during a November 1972 cruise on the USNS Bartlett offshore of central and southern California. Profiles were collected using a sparker sound source powered between 120 and 160 kJ and recorded using an analog hydrophone streamer with navigation fixes taken at 30- to 60-minute intervals using a LORAN navigation system. Data were written to paper rolls.
    Date: 17-Aug-2011 (process 2 of 4)
    Scanned copies of the original paper rolls were scanned to tiff and jpeg digital format. These images have subsequently been made available in the National Archive of Marine Seismic Surveys (NAMSS; Triezenburg and others 2016).
    Date: 10-Mar-2021 (process 3 of 4)
    Tiff image line parts were cropped, straightened, transposed, and merged by navigation line using Adobe Photoshop. Using Image2segy software (https://gma.icm.csic.es/ca/image2segy), raster seismic images were transformed to geo-referenced SEG-Y profiles using the original 30– to 60-minute navigation fixes. Assuming a survey speed of 8 knots (4 meters per second), shots were interpolated every 1.5 seconds resulting in 6-meter spacing between successive shots. Record delays were written to SEG-Y headers.
    Date: 10-Mar-2022 (process 4 of 4)
    The following process steps were applied using Shearwater’s Reveal seismic software (https://www.shearwatergeo.com/4/reveal-software): delay recording time shift, water column mute, bottom mute 2700 ms below the water bottom, time migration at a constant 1600m/s, 3 trace median gather filter, 0-10-150-200 Hz Bandpass filter, and a final water column mute and bottom mute.
  3. What similar or related data should the user be aware of?
    Triezenberg, Peter J., Hart, Patrick E., and Childs, Jonathan R., 2016, National Archive of Marine Seismic Surveys (NAMSS): A USGS data website of marine seismic reflection data within the U.S. Exclusive Economic Zone (EEZ).

    Online Links:

    Other_Citation_Details:
    Triezenberg, P.J., Hart, P.E., and Childs, J.R., 2016, National Archive of Marine Seismic Surveys (NAMSS): A USGS data website of marine seismic reflection data within the U.S. Exclusive Economic Zone (EEZ): U.S. Geological Survey data release, https://doi.org/10.5066/F7930R7P.
    Greene, H. Gary, Silver, Eli A., and Roland E. von Huene, 1975, Seismic reflection profiles November 1972 cruise, USNS Bartlett, offshore Central and southern California.

    Online Links:

    Other_Citation_Details:
    This USGS Open-File Report contains the hand-written seismic logs (field notes) from the acquisition cruise.

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

  1. How well have the observations been checked?
    Scanned copies of the original seismic-reflection data from paper rolls were provided by PG&E for this project. As these are scanned copies, an unknown loss of resolution may have occurred. These scanned copies of the original paper records are identified as the best available version and from which modern (c. 2021-2022) reprocessing of this legacy data occurred.
  2. How accurate are the geographic locations?
    Navigation fixes are only every 30 minutes to 1 hour using a LORAN navigation system that has a horizontal accuracy within tens of miles. Reprocessed data interpolates position for each trace using the original navigation fixes.
  3. How accurate are the heights or depths?
    Depths shown in 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?
    Navigation fixes are only every 30 minutes to 1 hour using a LORAN navigation system.

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 as the originator 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)
    pcmsc_data@usgs.gov
  2. What's the catalog number I need to order this data set? B-1-72-SC_UTM11N.zip contains reprocessed seismic-reflection (SEG-Y) data originally collected in 1972. The 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 reprocessed seismic-reflection data per navigation line from scans of the original paper records in format SEG-Y (version SEG-Y rev 1) Size: 1012.4
      Network links: https://doi.org/10.5066/P9EK7CG3
    • 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?

Dates:
Last modified: 28-Apr-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)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/CMGDS_DR_tool/DR_P9EK7CG3/B-1-72-SC_SoCal_UTM11N_metadata.faq.html>
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