Identification_Information: Citation: Citation_Information: Originator: Patrick E. Hart Originator: Deborah R. Hutchinson Originator: Myung Lee Publication_Date: 2005 Title: High-resolution multichannel seismic-reflection data acquired in the northern Gulf of Mexico, 2003 Series_Information: Series_Name: U.S. Geological Survey Open-File Report Issue_Identification: 05-XXX Publication_Information: Publication_Place: Menlo Park, CA Publisher: U.S. Geological Survey Online_Linkage: 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 2003 with the Research Vessel Gyre (G-1-03-GM). The data are available in binary and JPEG 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 JPEG 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 provide site survey information for the two JIP drilling sites/lease blocks (Keathley Canyon 195 and Atwater Valley 14). (b) To tie the new data to regional coverages in the Gulf. (c) To tie the Marion Dufresne coring sites into the regional MCS grid. (d) To provide baseline information for selecting targets for the August NRL/DOE Gyre cruise. The seismic profiles provide high-quality images with approximately 5 meters of vertical resolution and up to 2 km of subbottom 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 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 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 survey G-1-03-GM is available at . The data window for G-1-03-GM is -94.818 26.715 -89.239 29.345 (decimal degrees). Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20030429 Ending_Date: 20030516 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: -94.82 East_Bounding_Coordinate: -89.24 North_Bounding_Coordinate: +29.35 South_Bounding_Coordinate: +26.72 Keywords: Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: U.S. Geological Survey Theme_Keyword: USGS Theme_Keyword: Coastal and Marine Geology Program Theme_Keyword: CMGP Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: geoscientific Theme_Keyword: imageryBaseMapsEarthCover Theme_Keyword: oceans Theme: Theme_Keyword_Thesaurus: Olsen, L.M., G. Major, S. Leicester, K. Shein, J. Scialdone, H. Weir, S. Ritz, C. Solomon, M. Holland, R. Bilodeau, T. Northcutt, R. Vogel. 2004. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 5.1.1 [online: http://gcmd.nasa.gov/Resources/valids/keyword_list.html] Theme_Keyword: Gas Hydrates Theme_Keyword: AIRGUN ARRAYS Theme_Keyword: WATERGUNS Theme_Keyword: MULTICHANNEL FILTER RADIOMETERS Theme_Keyword: SEISMIC REFLECTION PROFILERS 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: G-1-03-GM Theme_Keyword: G1-03-GM Place: Place_Keyword_Thesaurus: Geographic Names Information System (GNIS) Place_Keyword: Gulf of Mexico Place: Place_Keyword_Thesaurus: none Place_Keyword: Northern Gulf of Mexico Place_Keyword: Mississippi Canyon Place_Keyword: Keathley Canyon Place_Keyword: Atwater Valley 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: USGS, MailStop 999, 345 Middlefield Road City: Menlo Park State_or_Province: CA Postal_Code: 94025-3561 Country: USA Contact_Voice_Telephone: (650) 329-5160 Contact_Electronic_Mail_Address: hart@usgs.gov Browse_Graphic: Browse_Graphic_File_Name: Browse_Graphic_File_Description: Map of Northern Gulf of Mexico showing areas of 2003 USGS seismic research cruise Browse_Graphic_File_Type: JPEG Cross_Reference: Citation_Information: Originator: Deborah R. Hutchinson Originator: Patrick E. Hart Publication_Date: 2003 Title: Cruise Report for G1-03-GM, USGS Gas Hydrates Cruise, R/V Gyre, 1-14 May 2003, Northern Gulf of Mexico Series_Information: Series_Name: USGS Open-File Report Issue_Identification: 03-474 Publication_Information: Publication_Place: Woods Hole, MA Publisher: U. S. Geological SurveyCross_Reference Other_Citation_Details: Cross_Reference: Citation_Information: Originator: Patrick E. Hart Originator: Alan K. Cooper Originator: David Twichell Originator: Myung Lee Originator: Warren Agena Publication_Date: 2002 Title: High-Resolution Multichannel Seismic-Reflection Data Acquired in the Northern Gulf of Mexico, 1998-99 Series_Information: Series_Name: USGS Open-File Report Issue_Identification: 02-368 Publication_Information: Publication_Place: Menlo Park, CA Publisher: U. S. Geological Survey Other_Citation_Details: 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: Cross_Reference: Citation_Information: Originator: United States Geological Survey (USGS), Coastal and Marine Geology (CMG) Publication_Date: 2005 Title: USGS Coastal & Marine Geology InfoBank, USGS CMG G-1-03-GM Metadata Online_Linkage: 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: Entity_and_Attribute_Overview: Graphic image file: Each profile is available as a JPEG 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 plus/minus 10 m. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: The vertical position was local sea level and there have been no corrections to a datum or for tidal variations. Lineage: Process_Step: Process_Description: 2003 multichannel seismic data acquisition: Acquisition and recording of air-gun and water-gun seismic reflection data. The source consisted of either a 13/13 cubic inch dual-chamber GI ("Generator-Injector") air gun, a 24/24 cubic inch GI 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 2 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: 2003 Process_Step: Process_Description: Multichannel data processing: A representative data processing sequence consisted of: 1. SEG-D input and resample to 1.0 millisecond; 2. Geometry assignment and sort to CDP at 5 m spacing; 3. Wavelet deconvolution (Derived wavelet using 3 shot gathers and 16-18 msec window); 4. Predictive deconvolution (1st-zero crossing, operator length = 60 msec and a single design window); 5. Trace edit ; 6. Single window balance; 7. Band-pass filtering; 8. Common-Offset DMO; 9. Velocity analysis and NMO; 10. Stack (12-fold where 10 m shot spacing, 6-fold where 20 m shot spacing, 4-fold where 30-m shot spacing); 11. True amplitude gain application on stacked data; 12. Post-stack 2nd-zero crossing deconvolution (Operator length = 30 msec and single design window); 13. Migration velocity analysis based on the stacking velocity: Iteratively adjusted; 14. Migration; 15. Post-stack 40-400 Hz band-pass filtering ; 16. Water-bottom mute. Process_Date: 2003 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: 2003 Process_Step: Process_Description: Open File preparation The migrated seismic profiles were converted from SEG-Y format to CGM plot files using Paradigm Focus software. Then the CGM files were converted to 300 dots per inch JPEG image file using Larson CGM to Image software. Process_Date: 2004 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: USGS, MailStop 999, 345 Middlefield Road City: Menlo Park State_or_Province: CA Postal_Code: 94025-3561 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: USGS, MailStop 999, 345 Middlefield Road City: Menlo Park State_or_Province: CA Postal_Code: 94025-3561 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 05-XXX 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 in this report 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, JPEG, ASCII Transfer_Size: 8 gigabytes Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: 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: 20050822 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: USGS, MailStop 999, 345 Middlefield Road City: Menlo Park State_or_Province: CA Postal_Code: 94025-3561 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