Seismic Reflection, Geometrics multi-channel streamer tracklines, USGS field activity 2017-003-FA, Mississippi River Delta front offshore of southeastern Louisiana (Esri polyline shapefile, GCS WGS 84)

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Frequently anticipated questions:

What does this data set describe?

Title:
Seismic Reflection, Geometrics multi-channel streamer tracklines, USGS field activity 2017-003-FA, Mississippi River Delta front offshore of southeastern Louisiana (Esri polyline shapefile, GCS WGS 84)
Abstract:
High resolution bathymetric, sea-floor backscatter, and seismic-reflection data were collected offshore of southeastern Louisiana aboard the research vessel Point Sur on May 19-26, 2017, in an effort to characterize mudflow hazards on the Mississippi River Delta front. As the initial field program of a research cooperative between the U.S. Geological Survey, the Bureau of Ocean Energy Management, and other Federal and academic partners, the primary objective of this cruise was to assess the suitability of sea-floor mapping and shallow subsurface imaging tools in the challenging environmental conditions found across delta fronts (for example, variably distributed water column stratification and widespread biogenic gas in the shallow subsurface). Approximately 675 kilometers (km) of multibeam bathymetry and backscatter data, 420 km of towed chirp data, and 550 km of multichannel seismic data were collected. Varied mudflow (gully, lobe), prodelta morphologies, and structural features were imaged in selected survey areas from Pass a Loutre to Southwest Pass.
Supplemental_Information:
Additional information on the field activity is available from https://cmgds.marine.usgs.gov/fan_info.php?fan=2017-003-FA.
  1. How might this data set be cited?
    U.S. Geological Survey, 2018, Seismic Reflection, Geometrics multi-channel streamer tracklines, USGS field activity 2017-003-FA, Mississippi River Delta front offshore of southeastern Louisiana (Esri polyline shapefile, GCS WGS 84): data release DOI:10.5066/F7X929K6, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts.

    Online Links:

    This is part of the following larger work.

    Baldwin, Wayne E., Ackerman, Seth D., Worley, Charles R., Danforth, William W., and Chaytor, Jason D., 2018, High-resolution geophysical data collected along the Mississippi River Delta front offshore of southeastern Louisiana, U.S. Geological Survey Field Activity 2017-003-FA: data release DOI:10.5066/F7X929K6, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Baldwin, W.E., Ackerman, S.D., Worley, C.R., Danforth, W.W., and Chaytor, J.D, 2018, High-resolution geophysical data collected along the Mississippi River Delta front offshore of southeastern Louisiana, U.S. Geological Survey Field Activity 2017-003-FA: U.S. Geological Survey data release, https://doi.org/10.5066/F7X929K6.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.552178
    East_Bounding_Coordinate: -88.881535
    North_Bounding_Coordinate: 29.161340
    South_Bounding_Coordinate: 28.781718
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5a958e99e4b06990606a7db3/?name=2017-003-FA_MCS_Tracklines_browse.jpg (JPEG)
    Thumbnail image of multi-channel seismic-reflection tracklines from the Mississippi River Delta front offshore of southeastern Louisiana.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 21-May-2017
    Ending_Date: 26-May-2017
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • string (70)
    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 WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
  7. How does the data set describe geographic features?
    2017-003-FA_MCS_Tracklines
    Multichannel seismic-reflection tracklines for survey 2017-003-FA along the Mississippi River Delta front. (Source: U.S. Geological Survey)
    FID
    Internal feature number. (Source: Esri) Sequential unique whole numbers that are automatically generated.
    Shape
    Feature geometry. (Source: Esri) Coordinates defining the features.
    linename
    Name of the trackline along which MCS data were collected in the format: survey ID (i.e. 2017003FA_) + file name (i.e. transit4). (Source: U.S. Geological Survey) Character set
    imagename
    Name of the PNG image file associated with the MCS survey line. The appended '.stk-brute' in the file name indicates that the image represents a constant velocity, common midpoint stack version of the multi-channel seismic data. (Source: U.S. Geological Survey) Character set
    CMP_start
    common midpoint at the start of the line. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1000
    Maximum:1600
    Units:common midpoint
    Resolution:1
    CMP_end
    common midpoint at the end of the line. (Source: U.S. Geological Survey)
    Range of values
    Minimum:1912
    Maximum:45122
    Units:common midpoint
    Resolution:1
    jd_start
    Julian day at the start of the survey line (DDD). Julian day is the integer number (although recorded here in text string format) representing the interval of time in days since January 1 of the year of collection. (Source: U.S. Geological Survey)
    Range of values
    Minimum:141
    Maximum:146
    Units:Julian day
    Resolution:1
    jd_end
    Julian day at the end of the survey line (DDD). (Source: U.S. Geological Survey)
    Range of values
    Minimum:141
    Maximum:146
    Units:Julian day
    Resolution:1
    year
    Year the survey was conducted (YYYY). (Source: U.S. Geological Survey)
    Range of values
    Minimum:2017
    Maximum:2017
    Units:year
    Resolution:1
    surveyid
    WHCMSC field activity identifier (e.g. "2017-003-FA" where 2017 is the survey year, 003 is survey number of that year, and FA is Field Activity). (Source: U.S. Geological Survey) Character set
    vehicleid
    Survey vessel name. (Source: U.S. Geological Survey) Character set
    deviceid
    Sonar device used to collect MCS data in the format: source (AA S-Boom or SIG mini sparker)/receiver (GeoEel). (Source: U.S. Geological Survey) Character set
    length_km
    Length of MCS data line in kilometers (UTM Zone 16N, WGS 84) calculated in the SQLite database.. (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.711
    Maximum:34.438
    Units:kilometers
    Resolution:0.001
    Entity_and_Attribute_Overview:
    Each polyline feature in this shapefile can be hyperlinked to a corresponding PNG brute stack image in a GIS (see the 2017-003-FA_MCS_Images.zip archive accompanying 2017-003-FA_MCS_Images_meta.xml available from the larger work citation). The fist, last, and multiple of 100 common midpoint features in 2017-003-FA_MCS_100cmp.shp (available from the larger work citation) correspond to the x-axis ticks on the PNG images.
    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: Wayne E. Baldwin
    Geologist
    384 Woods Hole Road
    Woods Hole, Massachusetts
    US

    508-548-8700 x2226 (voice)
    508-457-2310 (FAX)
    wbaldwin@usgs.gov

Why was the data set created?

This dataset contains common midpoint trackline navigation for approximately 550 km of multi-channel streamer seismic-reflection profiles collected by the U.S. Geological Survey during cruise 2017-003-FA along the Mississippi River Delta front offshore of southeastern Louisiana. This information allows for spatial correlation of brute stack seismic-reflection profiles images with other geophysical and sample data for investigating sea-floor morphology and geologic framework in the area.

How was the data set created?

  1. From what previous works were the data drawn?
    raw MCS data (source 1 of 1)
    U.S. Geological Survey, Unpublished Material, MCS trackline data.

    Type_of_Source_Media: disc
    Source_Contribution:
    Multichannel seismic-reflection data were shot using Applied Acoustics S-Boom or SIG mini sparker (ELC 1050 and 1200) sources powered by Applied Acoustics CSP-D (700 and 2400) power supplies. Both sparker and boomer sources were used to test their relative effectiveness in the delta front setting, and some lines were reoccupied with each source to provide comparative results over common sections of sea floor. Shots were recorded using a 150-m long 32-channel (50 m active section) solid-state Geometrics GeoEel streamer with 1.5625-m spaced groups connected to a Geometrics Streamer Power Supply Unit (SPSU). The seismic sources were towed from the center of the stern approximately 17 m (lines FA2017003_transit4 - FA2017003_sw8) and 22 m (lines FA2017003_sw9 - FA2017003_bonus3) aft and approximately 4 m starboard of the DGPS antenna, and the GeoEel streamer was towed approximately 3 m outboard of the port side of the vessel from a boom crane, with the center of the first and last active groups approximately 73 and 123 meters aft of the DGPS antenna, respectively. The S-Boom source was powered at 600 joules (200 J per plate) and deployed from the start of surveying up to 19:19 (UTC) 5/21/2017 (JD141), between 02:17 and 15:31 5/22/2017 (JD142), and between 20:06 5/22/2017 (JD142) and 10:08 5/23/2017 (JD143). SIG mini sparker sources were supplied between 200 and 500 joules and deployed between 15:31 and 20:04 5/22/2017 (JD142), and between 00:20 5/24/2017 (JD144) and 00:44 5/26/2017 (JD146). Geometrics CNT-1 seismic acquisition software (version 5.361) running on a Windows PC was used to control the multichannel system and digitally log traces in the Geometrics SEG-D format, and record GPS navigation coordinates to the SEG-D external headers. Data were acquired at shot rates of 0.5 and 1 s, record lengths between 400 and 800 milliseconds (ms), and a sample interval of 0.25 ms.
  2. How were the data generated, processed, and modified?
    Date: May-2017 (process 1 of 5)
    A SIOSEIS (version 2015.3.1) seismic processing software script (sio_segd2segy) was used to read Geometrics SEG-D formatted (SIOSEIS process SEGDDIN) traces and write them (SIOSEIS process DISKOX) to SEG-Y Rev. 1 format (IEEE floating point) for each line.
    This process step and all subsequent process steps were conducted by the same person - Wayne Baldwin. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Wayne E. Baldwin
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    (508) 548-8700 x2226 (voice)
    (508) 457-2310 (FAX)
    wbaldwin@usgs.gov
    Date: Nov-2017 (process 2 of 5)
    OpenCPS (version 3.3.0) seismic processing software was used to perform the following series of processing flows:
    1. 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 OpenCPS database table. Finally, Output wrote the traces to a new file "*.sht-raw.seis" in the internal OpenCPS format.
    2. geom.flow - Input read the "*.sht-raw.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 source shot and streamer geometry based on measured horizontal offsets from the DGPS antenna to the source (-17.35 or -22.35) and the centers of the first (1) and last (32) channel groups (-73.43/-112.8) of the active streamer section. The algorithm interpolated a sail line from the source shot positions (NRP_X and NRP_Y), then computed layback positions for the source shot and 32 channel groups for each FFID by translating them back along the sail line by their respective measured offsets. Midpoint positions along the sail line were also computed for each shot/receiver pair, allowing the traces to be binned by common midpoints (CMPs) spaced evenly (by 0.781 m) along the sail line. Output wrote the traces to a new file "*.sht-raw_geom.seis" in which the trace header words SRC_X, SRC_Y, REC_X, REC_Y, MPT_X, MPT_Y, BIN_X, BIN_Y, and OFFSET were populated to reflect the layback Source X and Y, layback Receiver X and Y, layback Source/Receiver Midpoint X and Y, and CMP BIN X and Y positions, as well as the offset value (computed by sqrt((REC_X - SRC_X) * (REC_X - SRC_X) + (REC_Y - SRC_Y) * (REC_Y - SRC_Y))) for each trace in the resulting CMPs. *A limitation of the ShotlineLayback module is the inability to layback source shot/receiver locations that would have occurred prior to the start of the interpolated sail line (i.e. it does not project the sail line backward). This results in erroneous computation of those shot/receiver locations and their respective midpoints, making them unable to be stacked by bin location in the subsequent step. Consequently, up to 40 dead traces exist at the start of each common midpoint stack profile.*
    3. brute_stack.flow - Input read the "*.sht-raw_geom.seis" file and sorted the traces to CMP/OFFSET. The Python module Butterworth applied an Obspy version (modified from Scipy version 0.17.1) of a zero-phase, four corner Butterworth bandpass filter to the traces, between 450 and 1800 Hz for data shot with the S-Boom, or between 350 and 1400 Hz for those shot with the mini sparker. NormalMoveout applied a travel time correction to each trace based on offset and a constant velocity of 1530 m/s (water column sound speed), as well as a 60 percent stretch mute with a 30 ms taper. Stack summed the traces within each CMP, computed the average amplitude for each trace sample, and wrote the computed samples to a single CMP trace, as well as averaging the Midpoint positions of the input traces and updating the header words MPT_X and MPT_Y with the resulting averaged values. Output wrote the stacked traces to a new file "*.stk-brute.seis" in the internal OpenCPS format.
    4. geom2geojson.flow - Input read the "*.stk-brute.seis" file and sorted the traces to CMP. The custom Python module Header2GeoJSON (developed by Nathan Miller of USGS-WHCMSC) exported the stacked trace navigation (using coordinates from the BIN_X and BIN_Y headers) as point features in the GeoJSON format. Attributes for CMP, BIN_X, BIN_Y, linename, surveyid, vehicleid, and deviceid were also included in the GeoJSON output.
    Date: Nov-2017 (process 3 of 5)
    A batch shell script, MCSGeojson2SQL, was executed on the output GeoJSON file from the previous step. First, ogr2ogr (version 2.1.1) was used to import the GeoJSON formatted CMP navigation point geometries into a Spatialite (version 4.3.0) enabled SQLite (version 3.21.0) database table, and in the process add fields for the coordinates converted from UTM Zone 16N WGS 84 meters to GCS WGS 84 decimal degrees. Second, GJpts2lines.py created two new database tables, one containing line geometries generated from the CMP point navigation (with sort order defined by the linename and CMP fields), and another containing CMP navigation filtered to maintain the first and last CMPs, and CMPs at multiples of 100.
    Date: Dec-2017 (process 4 of 5)
    The MCS trackline features were added (Add Data) into ArcMap (version 10.3.1) from the SQLite database, and then exported (Right click on database feature class > Data > Export Data) to the new Esri polyline shapefile 2017-003-FA_MCS_Tracklines.
    Date: 07-Aug-2020 (process 5 of 5)
    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
  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?
    Multichannel seismic-reflection data were navigated using a Wide Area Augmentation System (WAAS) enabled Hemisphere Differential GPS (DGPS) receiver, with an antenna mounted on an 01 deck port side rail 7.35 m from the stern of the R/V Point Sur. The seismic sources were towed from the center of the stern approximately 17 m (lines FA2017003_transit4 - FA2017003_sw8) and 22 m (lines FA2017003_sw9 - FA2017003_bonus3) aft and approximately 4 m starboard of the DGPS antenna. The 150-m long GeoEel 32-channel (50 m active section) streamer was towed approximately 3 m outboard of the port side of the vessel from a boom crane, with the center of the first and last active groups approximately 73 m and 123 m aft of the DGPS antenna, respectively. The Geometrics CNT-1 seismic acquisition software (version 5.361) logged the shot navigation coordinates to the to the SEG-D external header. Layback distance between the GPS antenna and the acoustic source and receivers were calculated in post processing (described in the processing steps). Although horizontal accuracy of WAAS enabled DGPS is estimated to be within 2 m, the actual accuracy is assumed to be coarser due to the additional uncertainty added from calculation of source/receiver layback and common midpoint positions.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    Sections of tracklines where navigation was recorded but no seismic data were logged are not included such as some turns and transits (e.g. FA2017003_sw13a, from which the CMPs prior to 1600 are not included because many of the raw traces contain no data). There are no lines FA2017003_transit1, FA2017003_transit2, FA2017003_transit3, or FA2017003_dw13. Troubleshooting of the seismic power source during line FA2017003_sw9 caused shots 3003 - 4343 to not be logged. As a result, there is a gap in the CMP navigation for FA2017003_sw9 (see 2017-003-FA_MCS_100cmp.shp and the accompanying 2017-003-FA_MCS_cmp-nav.csv available from the larger work citation), as well as a conspicuous artifact in the form of an abrupt vertical sea floor offset in the PNG brute stack image corresponding to those CMPs (contained in the MCS.zip folder accompanying 2017-003-FA_MCS_Images_meta.xml available from the larger work citation). Similarly, the power source was briefly suspended and restarted during line FA2017003_sw25 causing shots 1014 - 1146 to not be logged. While the resulting gap is evident in the CMP navigation, the effect is less conspicuous in the PNG brute stack image.
  5. How consistent are the relationships among the observations, including topology?
    Multichannel seismic-reflection profile data were collected continuously throughout the cruise except during a survey hiatus between 19:19 (UTC) 5/21/2017 (JD141) and 02:17 5/22/2017 (JD142), a period of inclement weather, rough sea state, and system malfunction between 10:45 5/23/17 (JD 143) and 00:20 5/24/17 (JD144), and within Louisiana state waters, where the cruise was not permitted to use the seismic sources. Sparker and boomer sources were used with the multichannel streamer during the cruise to test their relative effectiveness in the delta front setting, and some lines were reoccupied with each source to provide comparative results over common sections of sea floor. Substantial flux of freshwater from the Mississippi River caused rather low at several locations during the cruise, which reduced the effectiveness of the sparker source, which is predicated on operation in sea water conditions. During these periods, the boomer source was deployed instead. Line numbering begins at FA2017003_transit4 and ends at FA2017003_bonus3. The attribute field 'imagename' lists the PNG image of the brute stack profile that corresponds to each line feature (see MCS.zip folder accompanying 2017-003-FA_MCS_Images_meta.xml available from the larger work citation). One image exists for each feature.

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 redistributable 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
    Federal Center
    Denver, CO

    1-888-275-8747 (voice)
  2. What's the catalog number I need to order this data set? USGS data release 2017-003-FA MCS data from the Mississippi River Delta front area: includes the shapefile 2017-003-FA_MCS_Tracklines.shp, the browse graphic 2017-003-FA_MCS_Tracklines_browse.jpg, and the Federal Geographic Data Committee (FGDC) Content Standards for Digital Geospatial Metadata (CSDGM) metadata file 2017-003-FA_MCS_Tracklines_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?
    To utilize these data, the user must have software capable of reading shapefile format, or GIS software capable of utilizing web mapping or feature services.

Who wrote the metadata?

Dates:
Last modified: 07-Aug-2020
Metadata author:
U.S. Geological Survey
Attn: Wayne E. Baldwin
Geologist
384 Woods Hole Rd.
Woods Hole, MA

(508) 548-8700 x2226 (voice)
(508) 457-2310 (FAX)
wbaldwin@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_F7X929K6/2017-003-FA_MCS_Tracklines_meta.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:18:58 2021