Seismic Reflection, EdgeTech SB-424 Chirp profile images collected in the vicinity of Buffalo Reef, Michigan, within Lake Superior, during USGS field activity 2018-043-FA, (PNG Images)

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Frequently anticipated questions:

What does this data set describe?

Title:
Seismic Reflection, EdgeTech SB-424 Chirp profile images collected in the vicinity of Buffalo Reef, Michigan, within Lake Superior, during USGS field activity 2018-043-FA, (PNG Images)
Abstract:
In September 2018, the U.S. Geological Survey, in collaboration with the U.S. Army Corps of Engineers, conducted high-resolution geophysical mapping and sediment sampling to determine the distribution of historical mine tailings on the floor of Lake Superior. Large amounts of waste material from copper mining, locally known as “stamp sands,” were dumped into the lake in the early 20th century, with wide-reaching consequences that have continued into the present. Mapping was focused offshore of the town of Gay on the Keweenaw Peninsula of Michigan, where ongoing erosion and re-deposition of the stamp sands has buried miles of native, white-sand beaches. Stamp sands are also encroaching onto Buffalo Reef, a large area of cobble/boulder substrate that supports productive fisheries in the lake. The objectives of this cooperative mapping project are to develop a framework for scientific research and provide baseline information required for management of resources within the coastal zone of northern Michigan. High-resolution bathymetry and backscatter data reveal the irregular topography of the shallow, cobble-covered Buffalo Reef and the relatively smooth surface of finer-grained sediment that covers adjacent, deeper parts of the lake floor. Previous research used numerous sediment samples to determine the general distribution of mine tailings on the lake floor in this area, but little information exists on the extent and thickness of the surficial deposits. The main priority of this project is to image the near-surface stratigraphy, specifically the thickness of surficial sand and mud that threaten to cover the reef, with seismic-reflection profiling systems. In addition to continuous coverage of bathymetric and backscatter data, this report includes a dense grid of closely spaced seismic profiles, which will guide efforts to mitigate the environmental impacts of the shifting stamp sands.
Supplemental_Information:
Additional information on the field activity is available from https://cmgds.marine.usgs.gov/fan_info.php?fan=2018-043-FA.
  1. How might this data set be cited?
    U.S. Geological Survey, 20200318, Seismic Reflection, EdgeTech SB-424 Chirp profile images collected in the vicinity of Buffalo Reef, Michigan, within Lake Superior, during USGS field activity 2018-043-FA, (PNG Images): data release DOI:10.5066/P9K4HX8V, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Andrews, Brian D., Barnhardt, Walter A., Foster, David S., Irwin, Barry J., and Nichols, Alex R., 2020, High-resolution geophysical data collected in the vicinity of Buffalo Reef, Michigan, within Lake Superior, U.S. Geological Survey Field Activity 2018-043-FA: data release DOI:10.5066/P9K4HX8V, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation:Andrews, B.D., Barnhardt, W.A., Foster, D.S., Irwin, B.J., and Nichols, A.R., 2020, High-resolution geophysical data collected in the vicinity of Buffalo Reef, Michigan, within Lake Superior, U.S. Geological Survey Field Activity 2018-043-FA: U.S. Geological Survey data release, https://doi.org/10.5066/P9K4HX8V
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.239889
    East_Bounding_Coordinate: -88.132397
    North_Bounding_Coordinate: 47.225725
    South_Bounding_Coordinate: 47.152425
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5ddeb3a6e4b04a30051bb448?name=2018-043-FA_EdgeTech424_Images_browse.jpg (JPEG)
    Thumbnail image of chirp seismic-reflection profile example from Lake Superior, Michigan.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 18-Sep-2018
    Ending_Date: 25-Sep-2018
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: raster digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions, type Pixel
    2. What coordinate system is used to represent geographic features?
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    The PNG seismic reflection images can be hyperlinked to their corresponding trackline or shotpoint locations in ArcGIS using the shapefiles '2018-043-FA_Edgetech424_Tracklines.shp' or '2018-043-FA_Edgetech424_500sht.shp', respectively (available from the larger work citation). The images show two-way travel time (seconds) on the y-axis and distance along profile (annotation at 500 shot intervals) on the x-axis.
    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)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: David S. Foster
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    US

    508-548-8700 x2271 (voice)
    508-457-2310 (FAX)
    dfoster@usgs.gov

Why was the data set created?

These PNG images represent approximately 272 km of chirp seismic-reflection data collected by the U.S. Geological Survey during cruise 2018-043-FA along Traverse Bay, Lake Superior. This information allows for spatial correlation of chirp seismic-reflection profiles images with other geophysical and sample data for investigating lake-floor morphology and stratigraphy in the area. Images of each seismic profile were generated in order to provide portable and easily viewable alternatives to the SEGY versions of the data. Each profile image can be hotlinked to its corresponding trackline navigation contained within the Esri polyline shapefile '2018-043-FA_Edgetech424_Tracklines.shp'. Shot-point index marks along the top of the PNG images correlate to the positions of 500 shot intervals within the Esri point shapefile '2018-043-FA_Edgetech424_500sht.shp'.

How was the data set created?

  1. From what previous works were the data drawn?
    SEG-Y SB-424 data (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, SB-424 PNG image data.

    Type_of_Source_Media: disc
    Source_Contribution:
    Chirp seismic data were collected using an EdgeTech 3100 portable sub-bottom profiling system and an SB-424 towfish (4-24 kHz), which was towed from a port side davit on the R/V Rafael with the transducer approximately 2 m below the water line, and 8.5 meters astern of the DGPS antenna mounted atop the port side of the cabin. Chesapeake Technology SonarWiz (version 6.05.0011) seismic acquisition software was used to control the 3100 topside unit, digitally log trace data in the SEG-Y Rev. 1 format (IEEE floating point), and record GPS navigation coordinates to the SEG-Y trace headers (in arc seconds of Latitude and Longitude, multiplied by a scalar of 360000). Data were acquired using a 250 milliseconds (ms) shot rate, a 5-ms pulse length, and a 4 to 24 kHz frequency sweep at 30 to 50 percent power. Traces were recorded with a 23-microsecond sample interval over lengths of approximately 100 ms.
  2. How were the data generated, processed, and modified?
    Date: Sep-2019 (process 1 of 3)
    PROCESS STEP 1:
    SIOSEIS (version 2015.3.1), Shearwater Reveal (version 2019), and Seismic Unix (version 4.2) were used to process SEG-Y data, create navigation files, and plot images. The processing flow and scripts used to produce navigation files including trackline shapefiles are summarized below and in the following processing steps.
    1) SIOSEIS was used to read the raw SEG-Y files, extract the envelope-detected trace, renumber shots starting from one, and write out new SEG-Y files.
    2) Reveal was use to run the following flows:
    A) read_segy.flow - SegyTapeRead read the traces. HeaderMath and UTMLatLong were used to convert the source lat/lon positions from seconds of arc to decimal degrees, project them to UTM Zone 16N WGS 84 meters, and write each to new header words (NRP_LAT, NRP_LON, NRP_X, and NRP_Y). DBWrite wrote the UTM positions for the first channel of each FFID to an internal Reveal database table. Finally, Output wrote the traces to a new file "*.sht-raw.seis" in the internal OpenCPS format.
    B) layback_shift.flow - Input read the "*.seis" file and sorted the traces to FFID/CHANNEL. The custom Python module ShotlineLayback (developed by Nathan Miller of USGS-WHCMSC) was used to define the measured horizontal offset between the DGPS antenna and the SB-424 transducer (-8.5 m). The algorithm interpolated a sail line from the source shot positions (NRP_X and NRP_Y), then computed layback positions for the SB-424 shots by translating them back along the sail by the measured offset. ApplyStatic was used to shift the traces down by 2.7 ms to account for the approximate 2 m tow depth of the SB-424 (a sound speed of 1500 m/s was used). Output wrote the shifted traces to a new SEG-Y files in which the trace header words SRC_X, SRC_Y represent the calculated layback coordinates, and REC_X, REC_Y maintain the original DGPS coordinates.
    3) The SIOSEIS script read424 was used to read layback and static corrected SEG-Y files, write a Seismic Unix file, and extract SEG-Y trace header information, including shot number, pre-layback and layback longitude and latitude, year, Julian day, and time of day (UTC). Header information from each SEG-Y file was saved to text files after an AWK (no version) filter was used to maintain the first and last shots, shots at multiples of 100, 500, and shots with unique navigation coordinates. Geographic coordinates (WGS 84) were converted to UTM zone 16 N coordinates (WGS 84) using Proj (version 4.9.3). End shots and shots at multiples of 100 may not have unique navigation coordinates. Separate text files containing the first and last shots and even 500 shot intervals were also saved. A 500 shot interval was chosen because it corresponds to the annotation interval provided along the top of the seismic-reflection profile images. Read424 called a Python script 424inlbtoSQL18043.py, written by Wayne Baldwin (USGS-WHCMSC), which imported the CSV files to a Spatialite (version 3.21.0) enabled SQLite (version 3) database, creating two tables containing point geometries for the unique and 500 shot interval navigation. The script also created line geometries from the unique navigation (sorted by LineName and Shot) and wrote them to an additional database table. The tracklines are based on all the shot navigation.
    4) The SIOSEIS script siothresh_pltwbt was used to pick the water-bottom time from the layback corrected SEG-Y files, apply a swell filter to smooth water-bottom time picks and shift the trace data by the difference between the smoothed and unsmoothed water bottom time before writing the shifted trace data to a new SEG-Y file.
    5) The Seismic Unix script Plot424 read the swell filtered SEG-Y files, saved as Seismic Unix format, and creates 12-inch-high variable density plots of the chirp profiles from the swell filtered SEG-Y files, which are converted to PNG format using ImageMagick (version 6.9.3-4). Images show two-way travel time (seconds) along the y-axis (left margin) and shots along profile (labeled at 500 shot intervals) on the x-axis (along top of profile). Person who carried out this activity:
    David S. Foster
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    (508) 548-8700 x2271 (voice)
    (508) 457-2310 (FAX)
    dfoster@usgs.gov
    Date: 07-Aug-2020 (process 2 of 3)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 25-Jan-2021 (process 3 of 3)
    Changed the distribution format name from digital data to PNG to better represent the data. Changed the series issue from a URL to the DOI number. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  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?
  2. How accurate are the geographic locations?
    Although navigation is not stored in the images, positional accuracy is relevant to the accuracy of these data. The EdgeTech SB-424 subbottom profiler was towed from a port side davit on the R/V Rafael with the transducer approximately 2 m below the water line, and 8.5 meters astern of the DGPS antenna mounted atop the port side of the cabin. Navigation data for the SB-424 were collected using a Hemisphere Differential GPS (DGPS) receiver. Positioning data were recorded using Chesapeake Technology SonarWiz (version 6.05.0011) acquisition software, which logged positioning coordinates to individual trace headers SEG-Y format. DGPS horizontal positional accuracy is assumed to be within 2 m; the layback position of the transducer relative to the DGPS antenna was accounted for during processing.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Data were not collected on the following dates because of weather: September 20-21 (JD263-264).
  5. How consistent are the relationships among the observations, including topology?
    Processed seismic data were converted to PNG format for ease of seismic trace display. Quality control was conducted during processing.

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:
Public domain data from the U.S. Government are freely re-distributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? USGS data release 2018-043-FA SB-424 PNG imagery from Lake Superior, Michigan includes the zip archive 2018-043-FA_Edgetech424_Images.zip containing 61 PNG images named according to line convention, the browse graphic 2018-043-FA_Edgetech424_Images_browse.jpg, and the Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (CSDGM) metadata file 2018-043-FA_Edgetech424_Images_meta.xml.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with any PNG image viewing software. The zip files must be uncompressed in order to view the images.

Who wrote the metadata?

Dates:
Last modified: 25-Jan-2021
Metadata author:
U.S. Geological Survey
Attn: David S. Foster
Geologist
384 Woods Hole Rd.
Woods Hole, MA

(508) 548-8700 x2271 (voice)
(508) 457-2310 (FAX)
dfoster@usgs.gov
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P9K4HX8V/2018-043-FA_Edgetech424_Images_meta.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:19:02 2021