Chirp seismic-reflection and navigation data collected in Alaskan lakes and fjords following the 2018 Anchorage earthquake

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Frequently anticipated questions:

What does this data set describe?

Title:
Chirp seismic-reflection and navigation data collected in Alaskan lakes and fjords following the 2018 Anchorage earthquake
Abstract:
Chirp seismic-reflection data and associated navigation files were collected from lacustrine and fjord basins in southcentral Alaska following the 2018 Anchorage earthquake. These data were collected from a 25-foot Boston Whaler (R/V Moose Dancer),18-foot cataraft (R/V Enterprise), and the R/V Alaskan Gyre in the summers of 2020 and 2021 for use in regional hazard assessments relating to Alaska’s seismic hazards.
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=2021-612-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2020-615-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2020-625-FA
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?
    Singleton, Drake M., Brothers, Daniel S., Hill, Jenna C., Haeussler, Peter J., and Witter, Robert C., 20230706, Chirp seismic-reflection and navigation data collected in Alaskan lakes and fjords following the 2018 Anchorage earthquake: data release DOI:10.5066/P924775B, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Singleton, Drake M., Brothers, Daniel S., Hill, Jenna C., Haeussler, Peter J., and Witter, Robert C., 2023, Geophysical and core sample data collected in lakes and fjords of southcentral Alaska following the 2018 Anchorage earthquake: data release DOI:10.5066/P924775B, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Singleton, D.M., Brothers, D.S., Hill, J.C., Haeussler, P.J., and Witter, R.C., 2023, Geophysical and core sample data collected in lakes and fjords of southcentral Alaska following the 2018 Anchorage earthquake: U.S. Geological Survey data release, https://doi.org/10.5066/P924775B.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -151.490850
    East_Bounding_Coordinate: -148.537050
    North_Bounding_Coordinate: 62.520180
    South_Bounding_Coordinate: 60.071108
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 08-Aug-2020
    Ending_Date: 22-Jun-2021
    Currentness_Reference:
    Ground conditions 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 and navigation polylines in shapefile 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 (39)
    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.
      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?
    2021_612_2020_625_2020_615_chirp_nav.shp
    Chirp seismic navigation in polyline format (Source: U.S. Geological Survey)
    FID
    Internal feature number (Source: Esri) Sequential unique integers automatically generated
    Shape
    Feature Geometry (Source: Esri) Feature shape automatically generated
    Field1
    USGS Pacific Coastal and Marine Science Center (PCMSC) field activity identifier followed by line number. For Example, 2021-612_CH21_59 is line CH21_59 collected during field activity number 2021-612-FA. (Source: U.S. Geological Survey) Unique seismic line number appended to field activity ID generated by the USGS
    Length
    Calculated length of the line in kilometers (Source: U.S. Geological Survey)
    Range of values
    Minimum:1.07490
    Maximum:11.00757
    Units:kilometers
    Resolution:0.00001
    Entity_and_Attribute_Overview:
    Zip archive of seismic shots with time stamp in standard SEG-Y format. Data for individual seismic lines follow file name format of Field-Activity-Number_LINE#.sgy. For example, 2021-612_CH21_59.sgy is line number CH21_59 collected during field activity 2021-612-FA.
    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)
    • Drake M. Singleton
    • Daniel S. Brothers
    • Jenna C. Hill
    • Peter J. Haeussler
    • Robert C. Witter
  2. Who also contributed to the data set?
    USGS PCMSC Marine Facility personnel Rachel Marcuson assisted with Chirp seismic data acquisition.
  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?

Identification of fault-related submarine hazards is a primary mission of the USGS Coastal and Marine Hazards and Resources Program. Intraslab earthquakes, which occur at depth within the subducting plate, can cause intense shaking at the Earth’s surface, but do not cause surficial faulting or result in significant land level changes. The seismic shaking associated with intraslab earthquakes can remobilize subaqueous sediment and lead to gravity driven sediment flows, potentially creating a record of past shaking from these events. To gain a better understanding of the conditions that produce seismically triggered deposits in subaqueous basins the USGS collected Chirp seismic and sediment cores from several lakes and fjords following the M7.1 2018 Anchorage earthquake. These data are intended to further our understand of geologic hazard in southcentral Alaska, improve risk assessments for local communities and critical infrastructure, and to provide data for future research on regional paleoseismic records in southcentral Alaska.

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: 08-Aug-2020 (process 1 of 4)
    Field seismic data collection 2020-625-FA: Seismic data were collected onboard the R/V Moose Dancer using an EdgeTech SB-424 Chirp sub-bottom profiler. Field data were collected in JSF format. Navigation data were collected simultaneously with a Hemisphere V110 GPS and saved into the seismic headers during acquisition. Profiles Kel20-04 and Kel20-06 collected during 2020-625-FA experienced power loss in the tow-fish data cable resulting in loss of recorded data for a short period of time.
    Date: 12-Sep-2020 (process 2 of 4)
    Field seismic data collection 2020-615-FA: Seismic data were collected onboard the R/V Alaskan Gyre using an EdgeTech SB-516 Chirp sub-bottom profiler. Field data were collected in JSF format. Navigation data were collected simultaneously with a Hemisphere V110 GPS and saved into the seismic headers during acquisition.
    Date: 12-Jun-2021 (process 3 of 4)
    Field seismic data collection 2021-612-FA: Seismic data were collected onboard the R/V Enterprise using an EdgeTech SB-216 Chirp sub-bottom profiler. Field data were collected in JSF format. Navigation data were collected simultaneously with a Hemisphere V110 GPS and saved into the seismic headers during acquisition.
    Date: 01-Jun-2022 (process 4 of 4)
    The following processing flow was carried out in SioSeis (v. 2022.1.2) to process field data output to SEG-Y files: (1) Trace envelope data from field-collected JSF files were converted to SEG-Y format.
  3. What similar or related data should the user be aware of?

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

  1. How well have the observations been checked?
    Quality control of attribute accuracy was conducted during field data collection and processing workflows.
  2. How accurate are the geographic locations?
    A Hemisphere V110 GPS system was used for obtaining navigation data during the cruise with a stated accuracy of 0.6 meters (95 percent confidence). Horizontal position coordinates in WGS 84/UTM zone 6N reference frame are located in index position 73-80 within the segy header.
  3. How accurate are the heights or depths?
    Two-way travel time in milliseconds referenced to sea level is provided in the SEG-Y files. Referencing two-way travel time to sea level is accomplished via an internal pressure logger within the Chirp towfish with a stated accuracy of approximately 0.001 psi which is converted to water depth accurate to within approximately 1 cm. If this depth information is recorded, it is populated in the receiver group elevation header in the SEG-Y files (bytes 41-44). Data collected during Field Activity 2021-612-FA does not record internal pressure logger information, but instead was collected from fixed pole position at a water depth of 60 centimeters.
  4. Where are the gaps in the data? What is missing?
    Profiles Kel20-04 and Kel20-06 collected during 2020-625-FA experienced power loss in the tow-fish data cable resulting in loss of recorded data for a short period of time. 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?
    All SEG-Y and navigation data were derived from the same instruments and processing workflows. Paired navigation and SEG-Y files have corresponding filenames and/or corresponding names indicated in shapefile attribute fields.

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(s) 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? Seismic data are available in SEG-Y format (2021-612_2020-625_2020-615_chirp.zip) with navigation provided in a shapefile format (2021-612_2020-625_2020-615_chirp.nav.zip) and accompanied by CSDGM FGDC-compliant metadata.
  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 processed seismic data per single navigation line. Data for individual seismic lines follow file name format of Field-Activity-Number_LINE#.sgy. in format SEG-Y (version SEG-Y rev 1) Size: 4400
      Network links: https://doi.org/10.5066/P924775B
    • Cost to order the data: None.

  5. What hardware or software do I need in order to use the data set?
    Viewing SEG-Y data requires specialized software. A list of common SEG-Y processing and visualization software is available at http://www.oilfieldwiki.com/wiki/List_of_free_geophysics_software. Shapefile navigation data can be viewed using any Geographic Information System software (for example, ArcGIS, QGIS).

Who wrote the metadata?

Dates:
Last modified: 06-Jul-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_P924775B/2021-612_2020-625_2020-615_seismic_metadata_052223.06-13-2023.faq.html>
Generated by mp version 2.9.51 on Wed Jul 26 11:09:59 2023