Deep-Towed Chirp Profiles of the Blake Ridge Collapse Structure Collected on USGS cruises 92023 and 95023 Aboard the R/V Cape Hatteras in 1992 and 1995

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Frequently anticipated questions:

What does this data set describe?

Deep-Towed Chirp Profiles of the Blake Ridge Collapse Structure Collected on USGS cruises 92023 and 95023 Aboard the R/V Cape Hatteras in 1992 and 1995
This CD-ROM contains copies of the navigation and deep-towed chirp subbottom data collected aboard the R/V Cape Hatteras,on cruises 92023 and 95023 in 1992 and 1995 respectively. This CD-ROM is (Compact Disc-Read Only Memory UDF (Universal Disc Format) CD-ROM Standard (ISO 9660 equivalent). The HTML documentation is written utilizing some HTML 4.0 enhancements. The disk should be viewable by all WWW browsers but may not properly format on some older WWW browsers. Also, some links to USGS collaborators and other agencies are available on this CD-ROM. These links are only accessible if access to the Internet is available during browsing of the CD-ROM. On cruise 92023, 58 km of deep-towed chirp data were recorded on 4 lines and broken into a total of 8 files. 78 square kilometers of sidescan mosaic and approximately 1000 km of air gun single channel seismic reflection data were recorded as well but are not achived on this report. On cruise 95023, 100km of deep- towed chirp data were recorded on 5 lines and broken into 18 files. 152 square kilometers of sidescan mosaic and 244.3 km of GI gun single channel seismic reflection were also recorded but are not archived on this report. The archived Chirp subbottom data are in standard Society of Exploration Geologists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded for processing with software such as Seismic Unix or SIOSEIS. The subbottom data were recorded on the ISIS data acquisition system in QMIPS format. Chirp subbottom channel extracted from raw QMIPS format sonar files and converted to 16-bit Int. SEG-Y format using the program QMIPSTOSEGY. Even though the data are in SEG-Y format, it is not the conventional time series data (e.g. voltages or pressures), but rather instantaneous amplitude or envelope detected and therefore all of the amplitudes are positive (though not simply rectified).
Seismic reflection profiles are acquired by means of an acoustic source (usually generated electromagnetically or with compressed air), and a hydrophone or hydrophone array. Both elements are typically towed in the water behind a survey vessel, or some cases, mounted on side of the hull. The sound source emits a short acoustic pulse, which propagates through the water and sediment columns. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), and detected at the hydrophone. As the vessel moves, this process is repeated at intervals ranging between 0.5 and 20 meters depending on the source type. In this way, a two-dimensional image of the geologic structure beneath the ship track is constructed. For more information concerning seismic reflection profiling at the USGS Woods Hole . Additional information on the field activities these data pertain to can be found at: and .
  1. How might this data set be cited?
    Nealon, Jeffrey W., Dillon, William P., and Danforth, William W., 2001, Deep-Towed Chirp Profiles of the Blake Ridge Collapse Structure Collected on USGS cruises 92023 and 95023 Aboard the R/V Cape Hatteras in 1992 and 1995: U.S. Geological Survey Open-File Report 01-123, U.S. Geological Survey, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.03
    East_Bounding_Coordinate: -75.36
    North_Bounding_Coordinate: 32.03
    South_Bounding_Coordinate: 31.76
  3. What does it look like? (JPEG)
    Map of Chirp Survey Area
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 02-Oct-1992
    Beginning_Time: 164342
    Ending_Date: 16-Oct-1995
    Ending_Time: 205000
    data acquisition date range. These data are from 2 separate cruise. The first cruise occurred in 1992 from Sept. 21 to Oct. 4. The second cruise occurred in 1995 from Oct. 11 to Oct. 19.
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Horizontal X and Y UTM coordinates for each shot location are located in the SEG-Y trace headers, and latitude, longitude coordinates for each shot are also provided in ascii files extracted from the trace headers.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 18
      Scale_Factor_at_Central_Meridian: 9996
      Longitude_of_Central_Meridian: -75
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 5
      Ordinates (y-coordinates) are specified to the nearest 5
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodedic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298257.
      Altitude_Datum_Name: assumed sea level
      Altitude_Resolution: 1
      Altitude_Distance_Units: two-way travel time
      Altitude_Encoding_Method: Attribute values
      Depth_Datum_Name: local surface (sea level)
      Depth_Resolution: 1
      Depth_Distance_Units: meters
      Depth_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Jeffrey W. Nealon
    • William P. Dillon
    • William W. Danforth
  2. Who also contributed to the data set?
    Nealon, Jeffrey; Dillon, William; Danforth William; O'Brien Thomas
  3. To whom should users address questions about the data?
    Dillon, William P.
    U.S. Geological Survey
    Gas Hydrates Project
    384 Woods Hole Road
    Woods Hole, MA

    (508) 548-8700 (voice)
    (508) 457-2310 (FAX)

Why was the data set created?

This study was completed as part of an ongoing project in the field of natural gas hydrate research. Natural gas hydrates are an ice-like crystalline combination of water and gas, most commonly methane. The data included in this report were collected in an effort to understand a site where we believe large quantities of methane, approximately 4% of the present atmospheric total, was released from seafloor sediments. This site is known as the Blake Ridge collapse structure, located 300 km off the South Carolina coast at approximately 2600 m of water depth.

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: 2001 (process 1 of 3)
    The subbottom data were recorded on the ISIS data acquisition system in QMIPS format. Chirp subbottom channel extracted from raw QMIPS format sonar files and converted to 16-bit Int. SEG-Y format using the program QMIPSTOSEGY. The fish depth was recorded in two-way time (ms) in the delay field (byte 109) of the SEG-Y trace header. Person who carried out this activity:
    Danforth, William W.
    U.S. Geological Survey
    Seafloor Mapping Project
    384 Woods Hole Road
    Woods Hole, MA

    (508) 548-8700 (voice)
    (508) 457-2310 (FAX)
    Date: 13-Jun-2016 (process 2 of 3)
    Peter Schweitzer made several improvements to the metadata, most notably in the distribution section to provide the network resource links to download the data. Additionally, he add the ISO Topic Categories thesaurus and term, as well as the USGS Thesaurus and terms. He added the online link to the publications in the identification section, as well as the full link to the browse graphic. He also added information to the distribution section, specifically the digital transfer information with the links to download individual SEG-Y files as well as adding information with regards to the navigation files and links to download those individual files. These edits were used to improve the metadata file provided from Geo-NSDI. Part of his work included putting himself as the metadata contact. The original metadata indicates William Danforth as the metadata contact. Person who carried out this activity:
    Peter N Schweitzer
    USGS Midwest Area
    Collection manager, USGS Geoscience Data Clearinghouse,
    Mail Stop 954 12201 Sunrise Valley Dr
    Reston, VA

    703-648-6533 (voice)
    703-648-6252 (FAX)
    Date: 17-Nov-2021 (process 3 of 3)
    Edits to the metadata were made to fix any errors that MP v 2.9.50 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Minor edits to the structure of the metadata were performed such as removing extra carriage returns. The DOI link was added to the identification section. Added additional USGS Thesaurus terms. Added the links to the field activities related to these data. Updated the currentness reference to more accurately describe the range of dates and data. No attempt was made to add detailed entity and attribute information specific to the data. The user will need to reference the original Open-File Report for that information. Reorganized the digital transfer information slightly from what Peter had done. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent. Additional edits were probably made to the original metadata by someone else who did not document what they changed (20210406). Tweaked a thesaurus name (20211117). 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)
  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?
    The ship was navigated with differential GPS.
  3. How accurate are the heights or depths?
    The vertical position was local sea level and there was no correction to a datum or tides.
  4. Where are the gaps in the data? What is missing?
    All data referenced in the CD-ROM are present
  5. How consistent are the relationships among the observations, including topology?
    This data archive was collected on two cruises with a single collection platform, therefore while there may be differences between the two, each dataset is internally consistent.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints The U.S. Geological Survey must be referenced as the originator of the datasetin any future products or research derived from these data.
Use_Constraints None
  1. Who distributes the data set? (Distributor 1 of 1)
    Soderberg, Nancy
    U.S. Geological Survey
    Data Librarian
    384 Woods Hole Road
    Woods Hole, MA

    (508) 548-8700 (voice)
    (508) 457-2310 (FAX)
  2. What's the catalog number I need to order this data set? U.S. Geological Survey Open-File Report 01-123 CD-ROM. The CD-ROM contains Chirp data in SEG-Y format, shot point navigation, JPEG format files of the Chirp subbottom profiles. The Open-File report also contains additional information with regards to data acquisition, processing, and maps of navigation.
  3. What legal disclaimers am I supposed to read?
    This Compact Disc-Read Only Memory (CD-ROM) publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe upon privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Although all data published on this CD-ROM have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials.
  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 07-Jul-2022
Metadata author:
Danforth, William.
U.S. Geological Survey
Seafloor Mapping Group
384 Woods Hole Road
Woods Hole, MA

(508) 548-8700 (voice)
(508) 457-2310 (FAX)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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