High-resolution multichannel seismic-reflection data acquired in the northern Gulf of Mexico, 1998-99
Metadata also available as - [Questions & Answers] or as a [text file]
Metadata:
- Identification_Information:
Citation:
Citation_Information:
Originator: Patrick E. Hart
Originator: Alan K. Cooper
Originator: David Twichell
Publication_Date: 2002
Title:
High-resolution multichannel seismic-reflection data acquired in the northern Gulf of Mexico, 1998-99
Series_Information:
Series_Name: U.S. Geological Survey Open-File Report
Issue_Identification: 02-368
Publication_Information:
Publication_Place: Menlo Park, CA
Publisher: U.S. Geological Survey
Online_Linkage: <http://geopubs.wr.usgs.gov/open-file/of02-368/>
Geospatial_Data_Presentation_Form: seismic reflection profile section
Description:
Abstract:
This report consists of two-dimensional marine seismic reflection profile data from the northern Gulf of Mexico. These data were acquired in 1998 and 1999 with the Research Vessels Tommy Munro (M1-98-GM) and Gyre (G1-99-GM). The data are available in binary and GIF image formats. Binary data are in Society of Exploration Geologists (SEG) SEG-Y format and may be downloaded for further processing or display. Reference maps and GIF images of the profiles may be viewed with your Web browser.
Purpose:
Marine seismic reflection data are used to image and map sedimentary and structural features of the seafloor and subsurface. These data were acquired across the upper and middle continental slope of the northern Gulf of Mexico as part of an investigation of the of the seismic character, distribution, and potential effects of naturally-occurring marine gas hydrates and related free gas within the gas hydrate stability zone. The specific objectives of this investigation are (a) to produce high-resolution images of the gas hydrate stability zone; (b) to study the distribution and character of potential seafloor failures and their relationship to known and inferred gas hydrate deposits; (c) to look at systematic variations in subsurface structure in gas hydrate and non-hydrate areas; and (d) to estimate, if possible, the amounts of hydrates present within the gas hydrate stability zone. The seismic profiles provide high-quality images with approximately 5 meters of vertical resolution and up to 2 km of penetration.
Supplemental_Information:
Multichannel seismic reflection profiles are acquired by means of an acoustic source (usually compressed air discharged via an air gun or water gun), and a hydrophone array. Both elements are typically towed in the water behind a survey vessel. The sound source emits a short acoustic pulse, which propogates 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 10 and 30 meters depending on the source type. In this way a two-dimensional image of the geologic structure beneath the ship track is constructed.
Additional information about the USGS surveys M1-98-GM and G1-99-GM are available at <http://walrus.wr.usgs.gov/infobank/m/m198gm/html/m-1-98-gm.meta.html> <http://walrus.wr.usgs.gov/infobank/g/g199gm/html/g-1-99-gm.meta.html> The data window for M1-98-GM is -89.941 28.024 -88.995 28.656 (decimal degrees). The data window for G1-99-GM is -92.991 27.368 -91.429 27.944 (decimal degrees).
Time_Period_of_Content:
Time_Period_Information:
Multiple_Dates/Times:
Single_Date/Time:
Calendar_Date: 1998
Single_Date/Time:
Calendar_Date: 1999
Currentness_Reference:
Data assumed to be constant over time, but may change due to geologic processes.
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -93.00
East_Bounding_Coordinate: -89.00
North_Bounding_Coordinate: +28.67
South_Bounding_Coordinate: +27.37
Keywords:
Theme:
Theme_Keyword_Thesaurus: none
Theme_Keyword: marine seismic reflection
Theme_Keyword: gas hydrate
Theme_Keyword: air gun
Theme_Keyword: water gun
Theme_Keyword: multichannel
Theme_Keyword: SEG-Y
Theme_Keyword: M1-98-GM
Theme_Keyword: G1-99-GM
Place:
Place_Keyword_Thesaurus: none
Place_Keyword: Northern Gulf of Mexico
Place_Keyword: Mississippi Canyon
Access_Constraints: None. These data are held in the public domain.
Use_Constraints:
The U.S. Geological Survey requests to be acknowledged as the originator of the data in future products or derivative research.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Patrick E. Hart
Contact_Organization: U.S. Geological Survey
Contact_Position: geophysicist
Contact_Address:
Address_Type: mailing address
Address: Mail Stop 999, 345 Middlefield Rd.
City: Menlo Park
State_or_Province: CA
Postal_Code: 94025
Country: USA
Contact_Voice_Telephone: (650) 329-5160
Contact_Electronic_Mail_Address: hart@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name:
<http://geopubs.wr.usgs.gov/open-file/of02-368/images/cruisemap.jpg>
Browse_Graphic_File_Description:
Map of Northern Gulf of Mexico showing areas of USGS seismic research cruises
Browse_Graphic_File_Type: jpeg
Browse_Graphic:
Browse_Graphic_File_Name:
<http://geopubs.wr.usgs.gov/open-file/of00-368/images/99gif/41.gif>
Browse_Graphic_File_Description: Gulf of Mexico Line 41.gif (water-gun source)
Browse_Graphic_File_Type: gif
Cross_Reference:
Citation_Information:
Originator: Alan K. Cooper
Originator: Patrick E. Hart
Publication_Date: 2002
Title:
High-resolution seismic-reflection investigation of the northern Gulf of Mexico gas-hydrate-stability zone
Publication_Information:
Publication_Place: Great Britain
Publisher: Elsevier Sciences, Ltd
Other_Citation_Details: Marine and Petroleum Geology, in press
Cross_Reference:
Citation_Information:
Originator: Alan K. Cooper
Originator: Patrick E. Hart
Originator: Ingo Pecher
Publication_Date: 1998
Title:
Cruise report for a seismic investigation of gas hydrates in the Mississippi Canyon region, northern Gulf of Mexico - Cruise M1-98-GM,
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 98-506
Publication_Information:
Publication_Place: Menlo Park, CA
Publisher: U. S. Geological Survey
Other_Citation_Details: <http://geopubs.wr.usgs.gov/open-file/of98-506/>
Cross_Reference:
Citation_Information:
Originator: Alan K. Cooper
Originator: David Twichell
Originator: Patrick E. Hart
Publication_Date: 1999
Title:
A seismic-reflection investigation of gas-hydrates and sea-floor features of the upper continental slope of the Garden Banks and Green Canyon regions, northern Gulf of Mexico: Report for cruise G1-99-GM (99002)
Series_Information:
Series_Name: USGS Open-File Report
Issue_Identification: 99-570
Publication_Information:
Publication_Place: Menlo Park, CA
Publisher: U. S. Geological SurveyCross_Reference
Other_Citation_Details: <http://geopubs.wr.usgs.gov/open-file/of99-570/>
Cross_Reference:
Citation_Information:
Originator: Myung Lee
Originator: Patrick E. Hart
Originator: Warren Agena
Publication_Date: 2000
Title:
Processing Strategy for Water-Gun Seismic Data from the Gulf of Mexico
Series_Information:
Series_Name: USGS Bulletin
Issue_Identification: 2181
Publication_Information:
Publication_Place: Denver, CO
Publisher: U. S. Geological Survey
Other_Citation_Details: <http://greenwood.cr.usgs.gov/pub/bulletins/b2181/>
- Entity_and_Attribute_Information:
Overview_Description:
Entity_and_Attribute_Overview:
Binary data file: Each profile is available as a binary file in Society of Exploration Geophysicists SEG-Y format. A SEG-Y file consists of 1) a 3200-byte file identification record of EBCDIC encoded general information; 2) a 400-byte binary record with information such as sample rate and record length specific to the data set; and 3) multiple records, one seismic reflection trace per record. Each trace record is preceded by a 240-byte "trace header" containing information such as trace number and acquisition day and time specific to each trace. The trace data are represented as a time series of unitless 16-bit integer or 32-bit real numbers proportional to the pressure recorded at each hydrophone. The SEG-Y file is useful only if you have access to specialized software designed to process and display seismic reflection data.
Entity_and_Attribute_Detail_Citation:
Barry, K.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, v. 40, n. 2, p. 344 - 352. Also available online at: <http://www.seg.org/publications/tech-stand/index_body.html>
Entity_and_Attribute_Overview: Graphic image file: Each profile is available as a GIF image.
- Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
The validity or accuracy of marine seismic reflection profiles is highly qualitative, and depends on equipment and operating condition variables too numerous to quantify. There have been no efforts to assess the validity of the data.
Logical_Consistency_Report: These data have not been assessed for internal consistency.
Completeness_Report:
These are sparse line coverages (2D). Therefore, data are inherently incomplete. Geologic details between lines must be inferred. The surveys were not designed to cover a particular geographic area; the line spacings and azimuths were chosen to assess geologic features related to known and inferred gas hydrate deposits.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Positions were determined with differential Global Positioning System (GPS). Absolute position accuracy was approximately ± 10 m.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
The vertical position was local sea level and there has been no corrections to a datum or for tidal variations.
Lineage:
Process_Step:
Process_Description:
1998 multichannel seismic data acquisition: Acquisition and recording of air-gun and water-gun seismic reflection data. The source consisted of either a 35/35 cubic inch dual-chamber GI ("Generator-Injector") air gun or a 15 cubic inch water gun. The "injector" chamber of the GI gun was timed to discharge a short time (typically 20-30 msec) after the "generator" chamber so as to suppress the bubble pulse and create an optimal signal. The streamer was 240 meters in length with a 10-meter group interval (three hydrophones per group), and was manufactured by Innovative Transducers, Inc. (ITI) with solid-core construction and "thin-film" cylindrical hydrophones of polyvinylidene fluoride (PVDF) plastic. A problem with a streamer connection caused the far 7 channels to be very noisy, and these channels were eliminated during data processing. Data were digitized with the Geometrics Strataview seismograph and recorded with the Geometrics Marine Controller in SEG-D format.
Process_Date: 1998
Process_Step:
Process_Description:
1999 multichannel seismic data acquisition: The multichannel data acquisition equipment and parameters in 1999 were the same as 1998 except the 15 cubic inch water-gun source was used on all lines, and the recording problem with the far 7 streamer channels was corrected.
Process_Date: 1999
Process_Step:
Process_Description:
Multichannel data processing: A representative data processing sequence consisted of: 1. SEG-D input and resample to 0.5 millisecond 2. Trace edit 3. Geometry assignment 4. 50 Hz low-cut filter 5. Water-bottom mute 6. Deep-water recording delay correction 7. Spherical divergence correction 8. Noise-spike editing 9. FK filter 10. Deconvolution 11. Common midpoint (CMP) sort 12. Stacking velocity analysis 13. Normal move-out correction 14. Stack 15. SEG-Y output 16. 60-320 Hz bandpass filter 17. Whole-trace balance 18. gif image file output
Process_Date: 1999
Process_Step:
Process_Description:
Positional (navigation) data: As the seismic reflection data were acquired, the position of the vessel was continuously determined with the differnetial Global Positioning System (GPS). GPS positions were recorded approximately every second, and written to an ASCII file. This file was subsequently used to determine the position of each seismic reflection "shotpoint".
Process_Date: 199806, 199904
Process_Step:
Process_Description:
Open File preparation The data were plotted in 8-bit gray scale representation to Postscript files using the Seismic Unix 'psimage' algorithm at a scale of 0.15 seconds per inch and 75 traces per inch. The Postscript images were then converted to GIF with Aladdin Ghostview v5.50.
Process_Date: 2001
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Patrick E. Hart
Contact_Organization: U.S. Geological Survey
Contact_Position: geophysicist
Contact_Address:
Address_Type: mailing address
Address: Mail Stop 999, 345 Middlefield Rd.
City: Menlo Park
State_or_Province: CA
Postal_Code: 94025
Country: USA
Contact_Voice_Telephone: (650) 329-5160
Contact_Electronic_Mail_Address: hart@usgs.gov
- Spatial_Data_Organization_Information:
Indirect_Spatial_Reference:
Horizontal X and Y locations for each shot location are provided in ASCII position files.
- Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.00001
Longitude_Resolution: 0.00001
Geographic_Coordinate_Units: decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: WGS 84
Ellipsoid_Name: WGS 84
Semi-major_Axis: 6378137 m
Denominator_of_Flattening_Ratio: 298.257
- Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Patrick E. Hart
Contact_Organization: U.S. Geological Survey
Contact_Position: geophysicist
Contact_Address:
Address_Type: mailing address
Address: Mail Stop 999, 345 Middlefield Rd.
City: Menlo Park
State_or_Province: CA
Postal_Code: 94025
Country: USA
Contact_Voice_Telephone: (650) 329-5160
Contact_Electronic_Mail_Address: hart@usgs.gov
Contact_Instructions:
Data may be available off-line only by special arrangement with the distributor above. Please use the on-line download option unless precluded by download times or access difficulties.
Resource_Description: U.S. Geological Suvey Open-File Report 02-368
Distribution_Liability:
This dataset 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 for information, apparatus, products, or processes disclosed in this report, nor represents that its use would not infringe privately owned rights.
Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by 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. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data.
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: SEG-Y, GIF, ASCII
Transfer_Size: 12 gigabytes
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: <http://geopubs.wr.usgs.gov/open-file/of02-368/>
Offline_Option:
Recording_Format: ISO 9660
Offline_Media: CD-R or DVD-R
Fees: none
Technical_Prerequisites:
Use of SEG-Y data requires specialized software, such as ProMax and Seisworks by Landmark Geophysical; FOCUS and SeisX by Paradigm Geophysical; SPW by Parallel Geoscience; or VISTA by Seismic Image Software.
- Metadata_Reference_Information:
Metadata_Date: 20020916
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Patrick E. Hart
Contact_Organization: U.S. Geological Survey
Contact_Position: geophysicist
Contact_Address:
Address_Type: mailing address
Address: Mail Stop 999, 345 Middlefield Rd.
City: Menlo Park
State_or_Province: CA
Postal_Code: 94025
Country: USA
Contact_Voice_Telephone: (650) 329-5160
Contact_Electronic_Mail_Address: hart@usgs.gov
Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Generated by mp version 2.7.9 on Fri Sep 20 07:52:59 2002