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U.S. Geological Survey Data Series 526

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Identification_Information:
Citation:
Citation_Information:
Originator: Arnell S. Forde
Originator: Shawn V. Dadisman
Originator: James G. Flocks
Originator: Timothy M. Dellapenna
Originator: Jordan M. Sanford
Originator: Dana S. Wiese
Publication_Date: 2010
Title:
Archive of Digital Chirp Sub-bottom Profile Data Collected During USGS Cruise 09CCT01 Offshore of Sabine Pass and Galveston, Texas, March 2009
Geospatial_Data_Presentation_Form: Seismic Reflection Profile Section
Series_Information:
Series_Name: U.S. Geological Survey Data Series
Issue_Identification: 526
Publication_Information:
Publication_Place: St. Petersburg, FL
Publisher: U.S. Geological Survey
Description:
Abstract:
In March of 2009, the U.S. Geological Survey and Texas A&M University at Galveston conducted geophysical surveys to investigate the shallow geologic framework from Sabine Pass to Galveston, TX, as part of the USGS's Coastal Change and Transport (CCT) study. This report serves as an archive of unprocessed digital Chirp sub-bottom profile data, trackline maps, navigation files, GIS information, FACS logs, observer's logbook, and formal FGDC metadata. Gained digital images of the sub-bottom profiles are also provided.

The archived trace data are in standard SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided.

Purpose:
The data archived here were collected as part of the USGS's Coastal Change and Transport (CCT) study.
Supplemental_Information:
The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 09CCT01 tells us the data were collected in 2009 for the Coastal Change and Transport (CCT) study and the data were collected during the first field activity for that study in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the cruise or field activity ID. The naming convention used for each trackline is as follows: yye##a, where 'yy' are the last two digits of the year in which the data were collected, 'e' is a 1-letter abbreviation for the equipment type (for example, c for Chirp), '##' is a two-digit number representing a specific track, and 'a' is a letter representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems.

The Chirp system uses a signal of continuously varying frequency. The towfish is a sound source and receiver, which is typically towed 1 - 2 m below the sea surface. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by a receiver, and recorded by a PC-based sub-bottom acquisition system. This process is repeated at timed intervals (for example, 0.125 s) and recorded for specific intervals of time (for example, 50 ms). In this way, a two-dimensional vertical image of the shallow geologic structure beneath the ship track is produced.

The seismic source employed for Chirp data collection, during this cruise, consisted of an EdgeTech SB-512i towfish running Triton Imaging SB Logger (FSSB) version 1.6.500.9 acquisition software that was towed about 16.5 m behind the GPS antenna. The frequency range was 1 - 10 kHz (shallow) and 0.5 - 7.2 kHz (deep). Sample frequency of the data was 21 kHz, and record length was approximately 50 ms. Shot spacing was about 0.386 - 0.514 m.

For each recorded shot of the Chirp data, three channels of trace data are collected. Channel 2 is the "real," or in-phase component of the signal, channel 1 is the "imaginary," or quadrature component of the signal, and channel 0 is the "envelope," or product of channels 1 and 2. Only channel 0 was used to produce the profiles presented here. However, all channels are included in the SEG-Y data files.

The unprocessed sub-bottom data are stored in SEG-Y, integer, IBM format, which is a standard digital format that can be read and manipulated by most sub-bottom processing software packages (Barry and others, 1975). The SEG-Y formatted trace files have a .sgy extension. Also provided are example Seismic Unix scripts that allow the user to strip off navigation fixes from the SEG-Y headers, along with a fix for every 1,000 shots, and produce a gained GIF image of each profile.

The printable profiles provided here are GIF images that were gained using Seismic Unix software. The processed SEG-Y data were exported to CTI SonarWeb software to produce interactive, geospatial versions of the profiles, which allow the user to obtain a geographic location and depth from the profile for a cursor position. This information is displayed in the status bar of the browser. NOTE: The only supported Web browsers that properly display all features of the geospatial profiles are Internet Explorer 8 or greater for Windows and Firefox 3.6 or greater for all platforms. For all browsers, the status bar and JavaScript must be enabled. Firefox also requires "Change status bar text" to be checked under Advanced JavaScript Options. If using Internet Explorer 8, you must disable scripts/Active X controls. To do this, right click the information bar (found at the top of the page), left click "Allow Blocked Content...", and then select "Yes". Use of other browsers may result in spurious or no information given in the status window. Firefox may be downloaded at http://www.mozilla.org/products/firefox.

Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20090302
Ending_Date: 20090306
Currentness_Reference: Data collection interval
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -94.783943
East_Bounding_Coordinate: -93.568742
North_Bounding_Coordinate: 29.632306
South_Bounding_Coordinate: 28.993926
Keywords:
Theme:
Theme_Keyword_Thesaurus: None
Theme_Keyword: marine sub-bottom profile
Theme_Keyword: Chirp
Theme_Keyword: SEG-Y
Theme_Keyword: 09CCT01
Theme_Keyword: Coastal Change and Transport
Place:
Place_Keyword_Thesaurus: None
Place_Keyword: Texas
Place_Keyword: Galveston
Place_Keyword: Sabine Pass
Place_Keyword: Port Bolivar
Place_Keyword: East Bay
Place_Keyword: Gulf of Mexico
Access_Constraints: None. These data are held in the public domain.
Use_Constraints: The USGS and Texas A&M University request to be acknowledged as originators of the data in future products or derivative research.
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: James Flocks
Contact_Organization: USGS
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: Saint Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 803-8747 ext. 3012
Contact_Electronic_Mail_Address: jflocks@usgs.gov
Browse_Graphic:
Browse_Graphic_File_Name: DVD/maps/cruisenav/09cct01_location.jpg
Browse_Graphic_File_Description:
Location map of all digital sub-bottom profile data collected during USGS field activity 09CCT01. This map was created at a scale of 1:367,000. Refer to the Lineage section below for the trackline map creation process and other details.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name: DVD/maps/cruisenav/09cct01_area1.jpg
Browse_Graphic_File_Description:
Trackline map of digital sub-bottom profile data collected offshore of Sabine Pass (refer to Area 1 on the location map) during USGS field activity 09CCT01. This map was created at a scale of 1:232,000.
Browse_Graphic_File_Type: JPEG
Browse_Graphic:
Browse_Graphic_File_Name: DVD/maps/cruisenav/09cct01_area2.jpg
Browse_Graphic_File_Description:
Trackline map of digital sub-bottom profile data collected offshore of Galveston and East Bay (refer to Area 2 on the location map) during USGS field activity 09CCT01. This map was created at a scale of 1:360,000.
Browse_Graphic_File_Type: JPEG
Data_Set_Credit:
Funding for this study was provided by the USGS CMGP and Texas A&M University - Galveston, TX. We thank R/V Manta Captain Charles Curry of the National Oceanic and Atmospheric Administration (NOAA) for his assistance in data collection. This document was improved by the reviews of Gregory Miller (USGS - WHSC) and Julie Bernier (USGS - SPCMSC).

Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
The validity or accuracy of marine sub-bottom profiles is highly qualitative and depends on equipment and operating condition variables. Visual inspection of the images rendered from the data did not show any major anomalies.
Logical_Consistency_Report:
This data set is from one field activity with consistent instrument calibrations.
Completeness_Report:
These data are collected along tracklines (2-D) and are therefore inherently incomplete. Geologic details between lines must be inferred.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
As the sub-bottom profiles were acquired, the position of the vessel was continuously determined by a Coda Octopus F190 receiver, which is accurate to within 20 cm. Positions were recorded and written to the trace headers in latitude and longitude coordinates about every 1 s. The ASCII navigation files and trackline maps have not been corrected to reflect the approximately 17.10-m offset between the Chirp and GPS antenna. Refer to figure 1 included with this archive (Data Series 526) for a diagram of the acquisition geometry, including the GPS offset measurements. Line navigation maps and geospatial profiles generated with CTI SonarWeb software have been corrected for the GPS offset.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
These data are not to be used for bathymetry. Depths shown on the Chirp profiles are relative to the depth of the towfish, not to sea level. Furthermore, the raising or lowering of the towfish during a survey (to avoid obstacles or follow relief) produces a relative shift in the multiple reflections seen in the profile, which may be confused as a geologic feature. Any elevation change of the towfish should be recorded in the logbooks and is evident on the sub-bottom profiles by steep, abrupt shifts in the seafloor return.
Lineage:
Process_Step:
Process_Description:
Chirp processing: The original trace files for lines 09c02, 09c18, 09c24, 09c44, 09c45, 09c48, 09c65, 09c66, and 09c74 were divided into two or more trace files each (for example, 09c02 became 09c02_a and 09c02_b) because the original total number of traces exceeded the maximum allowed by the processing software. The SEG-Y data were processed with Seismic Unix to produce gained GIF images of the sub-bottom profiles included in this report. A representative Chirp data processing sequence consisted of (1) stripping off channel 0 for each shot and converting to SU format, (2) applying automatic gain control, (3) displaying PostScript, and (4) converting of PostScript image to a GIF image.

All the processed SEG-Y data were then exported to CTI SonarWeb software to produce an interactive, geospatial version of each profile that allows the user to obtain a geographic location and depth for a cursor position on the profile. Refer to the Supplemental Information section above for details on how to use the geospatial profiles.

Process_Date: 2009
Process_Step:
Process_Description:
Navigation processing: Shotpoint navigation files and 1,000-shot-interval location files were extracted from the trace headers of each line using Seismic Unix software. These files were then processed with PROJ.4 software (http://trac.osgeo.org/proj/) to generate UTM coordinates from latitude and longitude coordinates.
Process_Date: 2009
Process_Step:
Process_Description:
Trackline map creation: The trackline maps provided in this archive were created using the Points to Lines ArcScript (D. Rathert, http://arcscripts.esri.com/details.asp?dbid=12702) along with ESRI ArcGIS 9.3 software and then exported to Adobe Illustrator for further editing. The maps were later converted into JPEG format by Adobe GoLive version 8.0.1. The maps are unprojected (geographic coordinates, NAD83). The cities and interstates layers used on the trackline maps were created by ESRI. The USGS is the originator of all other layers used. A map of trackline navigation for each sub-bottom profile was also produced with CTI SonarWeb software.
Process_Date: 2009
Process_Step:
Process_Description:
Data Series preparation: In addition to the process steps described above, the following steps were taken to produce this Data Series: the handwritten logs were scanned and saved as PDF files, digital FACS logs were created using the handwritten logs and personal accounts of the crew members and saved as PDF files, and an HTML-based format was used to present the various parts of this archive.
Process_Date: 2009

Spatial_Data_Organization_Information:
Indirect_Spatial_Reference:
Horizontal X and Y locations (latitude and longitude coordinates) for each shot are provided as ASCII text files, along with the day of year and time (UTC) the shot was recorded.

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.0000027
Longitude_Resolution: 0.0000027
Geographic_Coordinate_Units: Decimal Degrees
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222

Entity_and_Attribute_Information:
Overview_Description:
Entity_and_Attribute_Overview:
Binary data file: Trace data are available as binary files in SEG-Y format. These files have a .sgy extension and range in size from 55 to 883 MB.
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, no. 2, p. 344-352. Also available on-line at: http://www.seg.org/SEGportalWEBproject/prod/SEG-Publications/Pub-Technical-Standards/Documents/seg_y_rev0.pdf.
Entity_and_Attribute_Detail_Citation:
Cohen, J.K., and Stockwell, J.W., Jr., 2005, CWP/SU: Seismic Unix Release 41: A free package for sub-bottom research and processing, Center for Wave Phenomena, Colorado School of Mines. Available on-line at http://www.cwp.mines.edu/cwpcodes/.
Entity_and_Attribute_Detail_Citation:
Zihlman, F.N., 1992, DUMPSEGY V1.0: A program to examine the contents of SEG-Y disk-image seismic data: U.S. Geological Survey Open-File Report 92-590, 28 p. Also available on-line at http://pubs.er.usgs.gov/usgspubs/ofr/ofr92590.
Entity_and_Attribute_Overview:
Graphic image file: Printable profiles are available as GIF images. Interactive profiles are available as HTML pages with accompanying JPEG images. The line navigation maps and trackline maps are JPEG images. The trackline maps contain links to the sub-bottom profiles and line navigation maps.
Entity_and_Attribute_Overview:
Navigation file: Navigation files are available as ASCII text files. Provided are raw (unprocessed) shotpoint navigation files, processed shotpoint navigation files, and processed 1,000-shot-interval location files.
Entity_and_Attribute_Overview:
GIS file: The GIS project used to create the trackline maps is provided as a .zip file composed of ESRI map documents, shapefiles, and metadata.

Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Arnell Forde
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 803-8747, ext. 3111
Contact_Electronic_Mail_Address: aharrison@usgs.gov
Contact_Instructions:
All of this report except the SEG-Y files is available on-line.
Resource_Description: U.S. Geological Survey Data Series 526
Distribution_Liability:
This DVD publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. 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.
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 following: a 3,600-byte reel identification header, with the first 3,200 bytes consisting of an ASCII header block followed by a 400-byte binary header block, both of which include information specific to line and reel number; a trace data block that follows the reel identification header, with the first 240 bytes of each trace block consisting of the binary trace identification header; and sub-bottom data samples that follow the trace identification header.
File_Decompression_Technique: None
Transfer_Size: 27.4 GB
Digital_Transfer_Option:
Offline_Option:
Offline_Media: DVD
Recording_Format: ISO 9660
Compatibility_Information: UNIX, Linux, DOS, Macintosh
Digital_Form:
Digital_Transfer_Information:
Format_Name: map document, shapefile, metadata
Format_Information_Content:
The GIS project used to create the trackline maps is composed of map documents, shapefiles, and metadata. Map documents were created with ESRI ArcGIS 9.3 software. The shapefiles provided may also be viewed using other versions of ArcView, ArcGIS, or public domain software ArcExplorer (http://www.esri.com/software/arcexplorer/).
File_Decompression_Technique: unzip
Transfer_Size: 19.4 MB
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name: DVD/software/arc/arc.zip
Fees:
Prices vary.
Ordering_Instructions:
Publications are available from USGS Information Services, Box 25286, Federal Center, Denver, CO 80225-0046 (telephone: 1-888-ASK-USGS, e-mail: infoservices@usgs.gov).
Technical_Prerequisites:
Use of SEG-Y data requires specialized sub-bottom processing software, such as public domain software Seismic Unix (http://www.cwp.mines.edu/cwpcodes/).

Metadata_Reference_Information:
Metadata_Date: 20100630
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Arnell Forde
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 803-8747, ext. 3111
Contact_Electronic_Mail_Address: aharrison@usgs.gov
Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998

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