Identification_Information: Citation: Citation_Information: Originator: Jeffrey W. Nealon Originator: William P. Dillon Originator: William W. Danforth Publication_Date: 2001 Title: Deep-Towed Chirp Profiles of the Blake Ridge Collapse StructureCollected on USGS cruises 92023 and 95023 Aboard the R/V Cape Hatterason in 1992 and 1995 Series_Information: Series_Name: U.S. Geological Survey Open-File Report Issue_Identification: 01-123 Publication_Information: Publication_Place: Woods Hole, MA Publisher: U.S. Geological Survey Description: Abstract: 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). Purpose: 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. Supplemental_Information: 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 //woodshole.er.usgs.gov/operations/sfmapping/> Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 19921002 Beginning_Time: 164342 Ending_Date: 19951016 Ending_Time: 205000 Currentness_Reference: Publication date Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -76.03 East_Bounding_Coordinate: -75.36 North_Bounding_Coordinate: 32.03 South_Bounding_Coordinate: 31.76 Keywords: Theme: Theme_Keyword_Thesaurus: None Theme_Keyword: seismic reflection Theme_Keyword: SEG-Y Theme_Keyword: Chirp Theme_Keyword: Datasonics SIS-7000 Theme_Keyword: high resolution Place: Place_Keyword_Thesaurus: None Place_Keyword: Atlantic Ocean Place_Keyword: Blake Ridge Place_Keyword: Blake Ridge collapse structure Place_Keyword: South Carolina Place_Keyword: Duke Marine Lab Place_Keyword: USGS Place_Keyword: Woods Hole Field Center (WHFC) Place_Keyword: Eastern Regional Center 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 Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Dillon, William P. Contact_Organization: U.S. Geological Survey Contact_Position: Gas Hydrates Project Contact_Address: Address_Type: mailing address Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Country: USA Contact_Voice_Telephone: (508) 548-8700 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: bdillon@usgs.gov Browse_Graphic: Browse_Graphic_File_Name: images/chirptracks.jpg Browse_Graphic_File_Description: Map of Chirp Survey Area Browse_Graphic_File_Type: JPEG Data_Set_Credit: Nealon, Jeffrey; Dillon, William; Danforth William; O'Brien Thomas Native_Data_Set_Environment: SEG-Y Data_Quality_Information: Logical_Consistency_Report: 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. Completeness_Report: All data referenced in the CD-ROM are present Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: The ship was navigated with differential GPS Quantitative_Horizontal_Positional_Accuracy_Assessment: Horizontal_Positional_Accuracy_Value: 5-10 meters Horizontal_Positional_Accuracy_Explanation: DGPS is assumed to be accurate within 5-10 meters Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: The vertical position was local sea level and there was no correction to a datum or tides. Lineage: Process_Step: Process_Description: 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. Process_Date: 2001 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Danforth, William W. Contact_Organization: U.S. Geological Survey Contact_Position: Seafloor Mapping Project Contact_Address: Address_Type: mailing address Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Country: USA Contact_Voice_Telephone: (508) 548-8700 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: wdanforth@usgs.gov Spatial_Data_Organization_Information: Indirect_Spatial_Reference: 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. Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 18 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 9996 Longitude_of_Central_Meridian: -75 Latitude_of_Projection_Origin: 0 False_Easting: 500000 False_Northing: 0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 5 Ordinate_Resolution: 5 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1983 Ellipsoid_Name: Geodedic Reference System 80 Semi-major_Axis: 6378137 Denominator_of_Flattening_Ratio: 298257 Vertical_Coordinate_System_Definition: Altitude_System_Definition: Altitude_Datum_Name: assumed sea level Altitude_Resolution: 1 Altitude_Distance_Units: two-way travel time Altitude_Encoding_Method: Attribute values Depth_System_Definition: Depth_Datum_Name: local surface (sea level) Depth_Resolution: 1 Depth_Distance_Units: meters Depth_Encoding_Method: Attribute values Distribution_Information: Distributor: Contact_Information: Contact_Person_Primary: Contact_Person: Soderberg, Nancy Contact_Organization: U.S. Geological Survey Contact_Position: Data Librarian Contact_Address: Address_Type: mailing address Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Country: USA Contact_Voice_Telephone: (508) 548-8700 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: nsoderberg@usgs.gov Resource_Description: U.S. Geological Survey Open-File Report 01-123 CD-ROM Distribution_Liability: 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. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: SEG-Y Format_Information_Content: The SEG-Y standard format (Barry and others, 1975) consists of the A 3600-byte reel identification header with the first 3200 bytes consisting of a EBCDIC header block and a 400-byte binary header block. Both headers include information specific to line and reel number. The trace data block follows the reel identification header. The first 240 bytes of each trace block is the binary trace identification header. The seismic data samples follow the trace identification header. File_Decompression_Technique: Gnu Zip Transfer_Size: 144 NB Digital_Transfer_Option: OffLine_Option: Offline_Media: CD-ROM Recording_Format: UDF Compatibility_Information: UNIX, DOS, MAC Fees: available from the Denver Open-File Sales department, price varies. Metadata_Reference_Information: Metadata_Date: 20010510 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Danforth, William. Contact_Organization: U.S. Geological Survey Contact_Position: Seafloor Mapping Group Contact_Address: Address_Type: mailing address Address: 384 Woods Hole Road City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Country: USA Contact_Voice_Telephone: (508) 548-8700 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: wdanfoth@usgs.gov Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: universal time Metadata_Access_Constraints: none Metadata_Use_Constraints: none 12:27 2001