Reprocessed multichannel seismic reflection data acquired offshore Southern California during USGS field activity L-4-90-SC

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Frequently anticipated questions:

What does this data set describe?

Title:
Reprocessed multichannel seismic reflection data acquired offshore Southern California during USGS field activity L-4-90-SC
Abstract:
Multichannel seismic (MCS) data were collected by the U.S. Geological Survey (USGS) in 1990 in the California Continental Borderland (USGS field activity L490SC). In 2021 these data were reprocessed to improve accuracy and resolvability of geologic structures and fault systems of California’s continental margin.
Supplemental_Information:
Additional information about the field activity from which these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=L490SC
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?
    Alongi, Travis, Balster-Gee, Alicia F., Kluesner, Jared W., and Sliter, Ray W., 20230809, Reprocessed multichannel seismic reflection data acquired offshore Southern California during USGS field activity L-4-90-SC: data release DOI:10.5066/P9FOES4K, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Alongi, T., Balster-Gee, A.F., Kluesner, J.W., Sliter, R.W., 2023, Reprocessed multichannel seismic reflection data acquired offshore Southern California during USGS field activity L-4-90-SC: U.S. Geological Survey data release, https://doi.org/10.5066/P9FOES4K.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -121.090570
    East_Bounding_Coordinate: -117.387666
    North_Bounding_Coordinate: 31.190785
    South_Bounding_Coordinate: 35.321160
  3. What does it look like?
    L490SC.preview.png (PNG)
    Map of MCS tracklines acquired during USGS field activity L-4-90-SC offshore Southern California.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 09-May-1990
    Ending_Date: 25-May-1990
    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?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (32)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is WGS 1984.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257224.
  7. How does the data set describe geographic features?
    L490SC.mcs.segy.zip
    Zip archive of seismic shots with time stamp in standard SEG-Y file format (Source: Society of Exploration Geophysicists (SEG) Technical Standards, available for download at http://seg.org/Publications/SEG-Technical-Standards)
    L490SC.mcs.trackline.shapefile.zip
    Zip file contains a polyline shapefile (.shp) of the location of each SEG-Y shot point along the navigated tracklines and associated files (Source: U.S. Geological Survey)
    LINE
    Number of navigation line (Source: Assigned unique line identifier name) Producer-assigned unique line identifier name
    Entity_and_Attribute_Overview:
    Seismic Shots with Time Stamp in standard SEG-Y file format, with trackline navigation presented in polyline shapefile 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)
    • Travis Alongi
    • Alicia F. Balster-Gee
    • Jared W. Kluesner
    • Ray W. Sliter
  2. Who also contributed to the data set?
    Reprocessing efforts were supported by an Interagency Agreement (IAA) between the Bureau of Ocean Energy Management (BOEM) and the U.S. Geological Survey. The authors acknowledge Danny Brothers (USGS) and Mark Leung (BOEM) for their role in coordinating the IAA. The authors also acknowledge the participants of the field activity L-4-90-SC, the crew of the R/V S.P. Lee and those involved in in survey planning and execution.
  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?

MCS data were acquired to support the Southern California Earthquake Hazards project to help mitigate earthquake and tsunami hazards for the Southern California region by improving our understanding of how deformation is distributed (spatially and temporally) in the offshore with respect to the onshore region. The reprocessed dataset enhances the seismic data quality which will be useful for future research on the geomorphic, sedimentary and tectonic history 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?
    original seismic-reflection data (source 1 of 1)
    Hart, P.E., 2016, namss.L-4-90-SC.mcs.airgun.zip: U.S. Geological Survey, online.

    Online Links:

    Type_of_Source_Media: online database
    Source_Contribution: seismic shot SEG-Y data for reprocessing
  2. How were the data generated, processed, and modified?
    Date: 20-May-1992 (process 1 of 2)
    Multichannel seismic-reflection data were acquired with a 10-airgun array seismic source with a combined chamber volume of 2424 cubic inches. The data were recorded using a 48-channel analog streamer which were spaced at 50 meter intervals, the furthest offsets was 2.4 kilometers aft of the airgun array. The length of the streamer and the 50 meter shot interval results in a fold of 20 traces or greater. The seismic traces were recorded at 2 ms sample rate with a total record length of 12 seconds. Data sources used in this process:
    • original seismic-reflection data
    Date: 20-May-2020 (process 2 of 2)
    Raw pre-stack SEG-Y data was imported into Reveal seismic software (https://www.shearwatergeo.com/4/reveal-software, v. 10.4.2019), where The seismic traces were detrended and the applied tape delay was removed. Corrections were applied to the SEG-Y headers which were recorded in reverse channel order and offsets were corrected to positive values. The preceding steps were applied to perform frequency - wavenumber analysis, with which noise and aliased signal were isolated and removed in Fourier space leaving the desired reflection signal. The raw data was quality controlled and 4 noisy channels at the furthest offsets were removed. The data was despiked, cleaned and trim statics were applied. Deconvolution wass done prestack and removed the source signature from the geologic reflections in order to produce crisp, collapsed, and high-resolution imaging. The deconvolution operator is an inverse filter that is computed statistically on a per-channel basis. The detailed 2D subsurface velocity structure was determined in a semblance analysis workflow. The velocity field was used to correctly move out the data before stacking to increase resolution, suppress random noise and reduce contamination from the sea surface multiple. Post-stack time migration was applied at 85 percent of the picked velocity for this data set. Finally, the water column was muted and the bottom edge of the data were muted. Data were exported to SEG-Y format with navigation in standard header byte locations and zipped into L490SC.mcs.segy.zip. CMP navigation was converted from points to a multi-line shapefile in QGIS-LTR (v. 3.21) and zipped into L490SC.mcs.trackline.shapefile.zip.
  3. What similar or related data should the user be aware of?
    Bohannon, R.G., Eittreim, S.L., and Childs, J.R., 1999, Cruise Report of R/V S.P. Lee, Leg 4, 1990, California continental borderland: U.S. Geological Survey Open-File Report 90-0502.

    Online Links:

    Other_Citation_Details:
    Bohannon, R.G., Eittreim, S.L., and Childs, J.R., 1990, Cruise Report of R/V S.P. Lee, Leg 4, 1990, California continental borderland: U.S. Geological Survey Open-File Report 90-0502, 10 p., http://pubs.usgs.gov/of/1990/0502/report.pdf.
    Fisher, Michael A., Langenheim, Victoria E., Nicholson, Craig, Ryan, Holly F., and Sliter, Ray W., 2000, Recent developments in understanding the tectonic evolution of the Southern California offshore area: Implications for earthquake-hazard analysis.

    Other_Citation_Details:
    Fisher, M.A., Langenheim, V.E., Nicholson, C., Ryan, H.F., and Sliter, R.W., 2009, Recent developments in understanding the tectonic evolution of the Southern California offshore area: Implications for earthquake-hazard analysis, in Lee, H.J., and Normark, W.R., (eds.) Earth Science in the Urban Ocean: The Southern California Continental Borderland: Geological Society of America Special Papers, v. 454, https://doi.org/10.1130/2009.2454(4.2).

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

  1. How well have the observations been checked?
    Quality control was conducted during acquisition. Some seismic profiles have gaps in them due to system crashes or intentional shutdowns as required, under terms of our operating permit, to protect marine mammals.
  2. How accurate are the geographic locations?
    The primary underway navigational sensor was Loran-C operated in the range-range mode. Loran-C calibration factors were derived from GPS solutions when GPS coverage was adequate(approximately 12 hours per day). The absolute accuracy of LORAN-C varies from 0.10 to 0.25 nmi (185 to 463 m). Repeatable accuracy is much greater, typically from 60 to 300 ft (18 to 91 m) (COMDTPUB P16562.6, "LORAN-C Users Handbook", 1992, https://chetaero.files.wordpress.com/2016/11/loran-c_users_handbook_entire.pdf). Further positional error may have been introduced from assigning receiver locations and CMP binning.
  3. How accurate are the heights or depths?
  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. Seismic data are unavailable where equipment failed and where marine mammal observers determined mammals were within the 250-m shutdown radius.
  5. How consistent are the relationships among the observations, including topology?
    Quality control was conducted during acquisition and processing to ensure consistency of SEG-Y header navigation and seismic-reflection data that matches bathymetry along the tracklines. Navigation data are available as a trackline shapefile in the ‘Data Files’ section. Trackline navigation combines SEG-Y line parts into a single-track line (32 tracklines and 32 SEG-Y files, including parts).

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? SEG-Y data are available in the zip file L490SC.mcs.segy.zip containing 32 standard SEG-Y format files of seismic shots with time stamp (Society of Exploration Geophysicists (SEG) Technical Standards, available for download at http://seg.org/Publications/SEG-Technical-Standards). A shapefile of the SEG-Y shot-track navigation is available in the zip file L490SC.mcs.trackline.shapefile.zip.
  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 (L490SC.mcs.segy.zip) contains the processed seismic data per navigation line. in format SEG-Y (version SEG-Y rev 1) Size: 489.1
      Network links: https://doi.org/10.5066/P9FOES4K
      Data format: Zip file contains a shapefile with SEG-Y trackline navigation in format shapefile (version ArcGIS Pro (version 2.4.1)) Size: 1.2
      Network links: https://doi.org/10.5066/P9FOES4K
    • 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 Reveal by Shearwater; 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. Users must have software capable of reading shapefile (.shp) format to use the shot point shapefile.

Who wrote the metadata?

Dates:
Last modified: 09-Aug-2023
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_P9FOES4K/L490SC.metadata.faq.html>
Generated by mp version 2.9.51 on Fri Aug 18 09:04:50 2023