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