Methane seep locations derived from water-column acoustic backscatter data collected along Cascadia Margin offshore Oregon and Northern California, 2018-2021

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Frequently anticipated questions:

What does this data set describe?

Title:
Methane seep locations derived from water-column acoustic backscatter data collected along Cascadia Margin offshore Oregon and Northern California, 2018-2021
Abstract:
This dataset contains the locations of 902 methane cold seeps that were detected in acoustic water-column backscatter collected by the U.S. Geological Survey between 2018 to 2021. Rising bubbles emitting from methane seeps on the seafloor can be detected acoustically with multibeam echo sounding sonar used to collected seafloor bathymetric mapping data, which the USGS and NOAA have cooperatively collected along the Cascadia Margin offshore of northern California and Oregon for several years.
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=2018-642-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2019-636-FA https://cmgds.marine.usgs.gov/fan_info.php?fan=2021-643-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?
    Conrad, James E., and Rudebusch, Jane A., 20230808, Methane seep locations derived from water-column acoustic backscatter data collected along Cascadia Margin offshore Oregon and Northern California, 2018-2021: data release DOI:10.5066/P9TW2X7Y, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Conrad, J.E., and Rudebusch, J.A., 2023, Methane seep locations derived from water-column acoustic backscatter data collected along Cascadia margin offshore Oregon and Northern California, 2018-2021: USGS data release, https://doi.org/10.5066/P9TW2X7Y.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -125.065269
    East_Bounding_Coordinate: -124.304200
    North_Bounding_Coordinate: 46.286529
    South_Bounding_Coordinate: 40.579799
  3. What does it look like?
    USGS_Cascadia_Seeps_2023.jpg (JPEG)
    A map of the Cascadia Margin showing the point locations of the seep flares contained in this dataset.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 31-Jul-2018
    Ending_Date: 09-Nov-2021
    Currentness_Reference:
    Ground conditions at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: point shapefile
  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 (902)
    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 D_WGS_1984.
      The ellipsoid used is WGS84.
      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: D_WGS_1984
      Depth_Resolution: 1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    Point
    A shapefile consisting of point locations indicating the geographic locations and depths of 902 fluid seeps on the seafloor of the Cascadia Margin. (Source: U.S. Geological Survey)
    FID
    Internal feature number (Source: Esri)
    Range of values
    Minimum:0
    Maximum:901
    Shape
    Feature Geometry (Source: Esri) The text ‘Point ZM’ indicating that objects area z-enabled features with point geometry
    Seep_No
    A unique identification number assigned to each seep feature. (Source: Producer defined) Each seep location was assigned a unique identifier consisting of an arbitrary two-letter prefix assigned according to the NOAA survey identifier of the location, followed by a sequential whole number. Note that the numbers are not all inclusive within the range - although they were assigned sequentially during seep detection, some were eliminated from the database because they were duplicates (located on adjacent or crossing survey lines) or later determined to not represent seep plumes.
    Line
    The file name of the water-column data and specified line identifier from which the seep was detected. (Source: Producer defined) The file name of the water-column data and specified line from which the seep was detected is assigned by NOAA during data acquisition and consists of a series of numbers and letters corresponding to the date, ship’s name, survey line, and sound receiver channel generally in the format ####_YYYYMMDD_#####_ShipName_LINE_RECCHAN#.
    Date
    Date of water-column data collection (Source: Producer defined)
    Range of values
    Minimum:08/01/2018
    Maximum:11/14/2021
    Units:month/day/year
    Time
    The timestamp of the acoustic ping where the seep registered in the water-column data. (Source: Producer defined)
    Range of values
    Minimum:00:16:07
    Maximum:23:37:08
    Units:UTC
    Longitude
    Geographic position of the seep in decimal degrees longitude. (Source: Ship GPS)
    Range of values
    Minimum:-124.304200
    Maximum:-125.065269
    Units:decimal degrees
    Resolution:0.000001
    Latitude
    Geographic position of the seep in decimal degrees latitude. (Source: Ship GPS)
    Range of values
    Minimum:40.579799
    Maximum:46.286529
    Units:decimal degrees
    Resolution:0.000001
    Depth
    The recorded depth measurement of the seep. (Source: Producer defined)
    Range of values
    Minimum:92
    Maximum:1372
    Units:meters
    Resolution:1
    Rise
    The maximum estimated height of the bubble plume observed in the water column. (Source: Producer defined)
    Range of values
    Minimum:4
    Maximum:1032
    Units:meters
    Resolution:1
    Comments
    Qualitative observations about the appearance, size, and/or quantity of the seep flares. (Source: Producer defined) Comments were made by J.E. Conrad to qualitatively describe the seep flares in terms of their size or quantity as they appeared in the water-column processing environment. Some fields are blank, meaning no notable observations were made about those seeps.
    SurveyID
    The identifier of the multibeam survey corresponding with the water column data and the associated seeps from that survey data. (Source: NOAA) The name of the multibeam survey from which the water-column data and seep location were derived. Survey IDs are assigned by NOAA and consist of a letter (H or W in this dataset) and a five-digit number. This ID can be used to search for the multibeam and water-column data used to create this dataset at NCEI.
    Entity_and_Attribute_Overview: Zip file of seep flare locations in shapefile format.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • James E. Conrad
    • Jane A. Rudebusch
  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?

These data were collected from a multibeam echosounder survey as part of the broader effort by the USGS Marine Geohazards Program to compile high-resolution bathymetric maps of the Cascadia Margin. These data are used to characterize the seafloor geomorphology to help understand geologic hazards posed by the megathrust fault and other tectonic features of the Cascadia subduction zone. Multibeam echo sounding sonar used to map the depth and topography of the seafloor also captures anomalies in the water column above the seafloor, such as rising fluid bubbles that produce strong acoustic reflectance in the imaging sonar. Globally, vast reserves of methane are stored beneath the seafloor that can seep up into the water column and can be detected with multi-beam echo sounder. The seeps in this dataset were detected in the water-column acoustic backscatter data and recorded for the purposes of understanding patterns in the distribution of fluid seepage along the margin.

How was the data set created?

  1. From what previous works were the data drawn?
    NOAA (source 1 of 1)
    NOAA, 20220128, Bathymetry data for H13117, H13118, H13206, H13119, H13137, H13549, W00474, and W00475: NOAA, online.

    Online Links:

    Type_of_Source_Media: Digital Resource
    Source_Contribution:
    Bathymetry data consisting of the .all and .wcd (water column data) files from surveys H13117, H13118, H13119, H13206, H13137, H13549, W00474, and W00475 were obtained from the NOAA National Centers for Environmental Information (NOAA NCEI).
  2. How were the data generated, processed, and modified?
    Date: 22-Feb-2023 (process 1 of 1)
    Bathymetry data from surveys H13117, H13118, H13119, H13206, H13137, H13549, W00474, and W00475 consisting of the .all and .wcd (water column data) files were loaded into QPS FMMidwater v 7.7.9 software running under the MacOS X Monterey operating system on an Apple MacBook Pro (2019) and converted into an internal .gwc format for water column inspection. These bathymetry data files, which typically consist of 30-minute segments of survey trackline, were then individually viewed simultaneously in an along-track view showing stacked acoustic pings and an across-track fan view usually configured to show 11 stacked acoustic pings. After adjusting acoustic backscatter gain levels to best show water column acoustic anomalies, the stacked water column data views are inspected using a survey data playback mode set to 15x or 30x normal speed. Upon recognition of seep plumes, playback mode is paused, the along-track view is switched to display a single-ping fan view of the data, and the data is manually stepped through ping-by-ping to best identify the seafloor and apparent top xyz locations of the seep plume, which are selected using a geopick tool. These locations, along with the date and time of the acoustic ping for each location, are then copied into a MS Excel spreadsheet for further analysis and import into GIS.
  3. What similar or related data should the user be aware of?
    Rudebusch, Jane A., Prouty, Nancy G., Conrad, James E., Watt, Janet T., Kluesner, Jared W., Hill, Jenna C., Miller, Nathaniel C., Watson, Sally J., and Hillman, Jess I.T., 2023, Diving Deeper Into Seep Distribution Along the Cascadia Convergent Margin, USA.

    Online Links:

    Other_Citation_Details:
    Rudebusch, J.A., Prouty, N.G., Conrad, J.E., Watt, J.T., Kluesner, J.W., Hill, J.C., Miller, N.C., Watson, S.J., Hillman, J.I.T. 2023. Diving Deeper into Methane Seep Distributions Along the Cascadia Convergent Margin, USA. Frontiers in Earth Science.

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

  1. How well have the observations been checked?
    The location and depth values recorded in this dataset were derived directly from the dataset’s co-located multibeam bathymetry, and therefore values are considered to have the level of accuracy to that of the multibeam data itself. Accuracy estimates of multibeam positional (x,y,z) coordinates is explained further in this metadata document.
  2. How accurate are the geographic locations?
    Ship position data were provided by a Differential Global Positioning System navigation receiver with +/- 10-centimeter accuracy. The acquired water column acoustic data used for seep detection, however, are not corrected for water column diffraction. Positional error in seep locations resulting from this is negligible at nadir (directly below the ship) and increases outward in the acoustic beams perpendicular to the ship track. Although no formal accuracy assessment of the horizontal positional information in the data set has been conducted, comparison of locations of seeps detected in multiple survey tracklines indicates that horizontal positional errors are less than about 10 meters in the outer survey beams.
  3. How accurate are the heights or depths?
    The acquired water-column acoustic data used for seep detection are not corrected for water-column diffraction, and no formal accuracy assessment of the horizontal positional information in the data set has been conducted. Comparison of depth values from gridded NOAA bathymetric data to those determined from water column data at seep sites indicate that the vertical positional accuracy varies from about +/- 3 meters on smooth sea floors to about +/- 10 meters in areas of steep slopes, rough seafloor, and in the outer beams of the water-column data.
  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?
    No formal logical consistency tests were conducted.

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.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - CMGDS
    2885 Mission Street
    Santa Cruz, CA

    1-831-427-4747 (voice)
    pcmsc_data@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available in shapefile format (USGS_Cascadia_Seeps_2023.shp and associated files) contained in a single zip file (USGS_Cascadia_Seeps_2023.zip) 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 point shapefile of seep locations. in format shapefile (version ArcGIS Pro (version 3.0.1)) Size: 0.0662
      Network links: https://doi.org/10.5066/P9TW2X7Y
    • Cost to order the data: None.

  5. What hardware or software do I need in order to use the data set?
    Shapefile navigation data can be viewed using any Geographic Information System (GIS) software (for example, ArcGIS, QGIS).

Who wrote the metadata?

Dates:
Last modified: 08-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_P9TW2X7Y/USGS_Cascadia_Seeps_2023_metadata.faq.html>
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