U.S. Geological Survey Data Series 259

FGDC Metadata

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Originator: Arnell S. Harrison
Originator: Shawn V. Dadisman
Originator: Nick F. Ferina
Originator: Dana S. Wiese
Originator: James G. Flocks
Publication_Date: 2007
Archive of Digital CHIRP Seismic Reflection Data Collected During USGS Cruise 06SCC01 Offshore of Isles Dernieres, Louisiana, June 2006
Geospatial_Data_Presentation_Form: Seismic Reflection Profile Section
Series_Name: U.S. Geological Survey Data Series
Issue_Identification: 259
Publication_Place: St. Petersburg, FL
Publisher: U.S. Geological Survey
In June of 2006, the U.S. Geological Survey conducted a geophysical survey offshore of Isles Dernieres, Louisiana. This report serves as an archive of unprocessed digital CHIRP seismic reflection data, trackline maps, navigation files, GIS information, Field Activity Collection System (FACS) logs, observer's logbook, and formal FGDC metadata. Gained digital images of the seismic profiles are also provided.

The archived trace data are in standard Society of Exploration Geophysicists (SEG) 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.

The data archived here were collected as part of the USGS Barrier Island Coastal Monitoring project, which is part of a broader study focused on Subsidence and Coastal Change (SCC).
The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 06SCC01 tells us the data were collected in 2006 for the Subsidence and Coastal Change (SCC) 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 ID. The naming convention used for each seismic line 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, b for boomer and c for CHIRP), ## is a 2-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 2-5 m above the seafloor. 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 seismic 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 consisted of an EdgeTech SB-424 towfish running Triton Imaging SB Logger (FSSB) V.1.6.421 acquisition software and towed about 10-m behind the GPS antenna. The frequency range was 4-20 kHz. Sample frequency of the data was 25 kHz, and record length was 30 ms. Shot spacing was about 0.668 m. During data collection, a vertical striped pattern was observed in the profiles. This anomaly was caused by an acquisition software malfunction that resulted in zero values being recorded for traces at miscellaneous intervals.

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 printable profiles provided here are GIF images that were gained using Seismic UNIX software. The processed SEG-Y data were exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce interactive versions of the profiles that 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 that the only supported Web browsers that properly display all features of the interactive profiles are Internet Explorer 6 for Windows and Firefox 1.5 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 Settings. 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.

Post-processing of the data also revealed the first shot value to be something other than one. The year and date were also omitted from the SEG-Y headers. A conversion program called FixPing V.1.0.0 was run to correct these three errors.The unprocessed seismic data are stored in SEG-Y, 4-byte integer format, which is a standard digital format that can be read and manipulated by most seismic processing software packages (Barry and others, 1975). The SEG-Y formatted trace files have a .SEG 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.

Beginning_Date: 20060608
Ending_Date: 20060630
Currentness_Reference: Data collection interval
Progress: Complete
Maintenance_and_Update_Frequency: None planned
West_Bounding_Coordinate: -90.952029
East_Bounding_Coordinate: -90.757764
North_Bounding_Coordinate: 29.033517
South_Bounding_Coordinate: 28.98394
Theme_Keyword_Thesaurus: None
Theme_Keyword: marine seismic reflection
Theme_Keyword: CHIRP
Theme_Keyword: SEG-Y
Theme_Keyword: 06SCC01
Theme_Keyword: Subsidence and Coastal Change
Theme_Keyword: Barrier Island Coastal Monitoring
Place_Keyword_Thesaurus: None
Place_Keyword: Louisiana
Place_Keyword: Isles Dernieres
Place_Keyword: Caillou Bay
Place_Keyword: Whiskey Pass
Place_Keyword: Lake Pelto
Place_Keyword: Gulf of Mexico
Access_Constraints: None. These data are held in the public domain.
The U.S. Geological Survey requests to be acknowledged as originator of the data in future products or derivative research.
Contact_Person: Nick Ferina
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
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. 3137
Contact_Electronic_Mail_Address: nferina@usgs.gov
Browse_Graphic_File_Name: DVD/maps/cruisenav/06scc01_location.jpg
Location map of all digital CHIRP seismic reflection data collected during USGS Cruise 06SCC01. This map was created at a scale of 1:522,159. Refer to the Lineage section below for the trackline map creation process.
Browse_Graphic_File_Type: JPEG
Browse_Graphic_File_Name: DVD/maps/cruisenav/06scc01_survey.jpg
Trackline map of digital CHIRP seismic reflection data collected in the survey area (refer to survey area on the location map) during USGS Cruise 06SCC01. This map was created at a scale of 1:129,085. Refer to the Lineage section below for the trackline map creation process.
Browse_Graphic_File_Type: JPEG
Funding and (or) support for this study were provided by the USGS Coastal and Marine Geology Program and the University of New Orleans. We thank R/V G.K. Gilbert captain Richard W. Young of the USGS in St. Petersburg, Florida, for his assistance in data collection. We also thank Karynna Calderon of CSC in St. Petersburg, Florida, for her assistance in data archiving. This document was improved by the reviews of Kate Ciembronowicz (ETI) and Dennis Krohn (USGS) of the FISC in St. Petersburg, Florida.

The validity or accuracy of marine seismic reflection profiles is highly qualitative and depends on equipment and operating condition variables. Visual inspection of the images rendered from the data showed that intermittently during data collection, a vertical striped pattern was observed in the profiles. This anomaly was caused by an acquisition software malfunction that resulted in repetitious zero values for traces when the record length was set to less than 50 ms. The cause of the malfunction was not determined until after the cruise. Refer to figure 2 included with this archive for an illustration of this acquisition anomaly.
This data set is from one cruise with consistent instrument calibrations.
These data are collected along tracklines (2-D) and are therefore inherently incomplete. Geologic details between lines must be inferred.
As the seismic reflection data were acquired, the position of the vessel was continuously determined by a Coda Octopus F190 receiver, which is accurate to within 20 centimeters. 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 10 m offset between the CHIRP and GPS antenna. Refer to figure 1 included with this archive (Data Series 259) for a diagram of the acquisition geometry, including the GPS offset measurements. Line navigation maps and interactive profiles generated with CTI SonarWeb software have been corrected for the GPS offset.
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 is recorded in the logbooks and is evident on the seismic profiles by steep, abrupt shifts in the seafloor return.
CHIRP processing: The SEG-Y data were processed with Seismic UNIX to produce GIF images of the seismic 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. The processed SEG-Y data were then exported to CTI SonarWeb software to produce an interactive version of each profile that allows the user to obtain a geographic location and depth from the profile for a cursor position. Refer to the Supplemental Information section above for details on how to use the interactive profiles.
Process_Date: 2006
SEG-Y header processing: All lines were first processed with FixPing V.1.0.0 software to correct first shot values that were other than one and add the year and dates, which were omitted from the trace headers. These corrected SEG-Y files are included in this archive.
Process_Date: 2006
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://www.remotesensing.org/proj) to generate UTM coordinates from latitude and longitude coordinates and reformatted for use with Environmental Systems Research Institute (ESRI) GIS software.
Process_Date: 2006
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 9.1 software and then exported to Adobe Illustrator for further editing. The maps were later converted into JPEG format by Adobe GoLive. The maps are unprojected (geographic coordinates, NAD83). The coastline layer is a Louisiana Oil Spill Coordinator's Office (LOSCO) dataset. The USGS is the originator of all other layers used. A map of trackline navigation for each seismic profile was also produced with CTI SonarWeb software.
Process_Date: 2006
Data Series preparation: In addition to the process steps described above, the following steps were taken to produce this Data Series report: 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: 2006

Horizontal X and Y locations (latitude and longitude and Zone 15 UTM coordinates) for each shot are provided as ASCII text files, along with the date and time (UTC) the shot was recorded.

Latitude_Resolution: 0.0000027
Longitude_Resolution: 0.0000027
Geographic_Coordinate_Units: decimal degrees
Horizontal_Datum_Name: WGS84
Ellipsoid_Name: WGS84
Semi-major_Axis: 6378137
Denominator_of_Flattening_Ratio: 298.257

Binary data file: Trace data are available as binary files in SEG-Y format. These files have a .SEG extension and range in size from 55 to 102 MB.
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 online at http://www.seg.org/publications/tech-stand.
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.
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 seismic profiles and line navigation maps.
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.
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.

Contact_Person: Shawn Dadisman
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
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. 3029
Contact_Electronic_Mail_Address: sdadisman@usgs.gov
Data may be available on-line only by special arrangement with the distributor above.
Resource_Description: U.S. Geological Survey Data Series 259
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, or for general or scientific purposes, 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 therein. Reference therein 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.
Format_Name: SEG-Y
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 seismic data samples that follow the trace identification header.
File_Decompression_Technique: None
Transfer_Size: 597 MB
Offline_Media: DVD
Recording_Format: ISO 9660
Compatibility_Information: UNIX, Linux, DOS, Macintosh
Format_Name: map document, shapefile, metadata
The GIS project used to create the trackline maps is composed of map documents, shapefiles, and metadata. Map documents were created with ESRI ArcGIS 9.1 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/index.html).
File_Decompression_Technique: unzip
Transfer_Size: 41.1 MB
Network_Resource_Name: DVD/software/arcgis/arc.zip
Prices vary.
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).
Use of SEG-Y data requires specialized seismic processing software, such as public domain software Seismic UNIX (http://www.cwp.mines.edu/cwpcodes/index.html).

Metadata_Date: 20070301
Contact_Person: Arnell Harrison
Contact_Organization: ETI, contracted by U.S. Geological Survey
Contact_Position: Geologist
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

Home | Acronyms | Contents | Navigation | Profiles | Logs | Metadata | Software