Data Series 924
U.S. Geological Survey, St. Petersburg, FL, 33701.
U.S. Department of the Interior
U.S. Geological Survey
St. Petersburg Coastal and Marine Science Center
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).
Page Contents: |
Figure 1. Regional map showing the August 2013 geophysical survey area, offshore of Petit Bois Island, Mississippi, during U.S. Geological Survey (USGS) field activity 13CCT04. Base map modified from USGS 1:100,000-scale Digital Line Graph data (World Geographic System 1984 (WGS84)). |
This Digital Versatile Disc (DVD) publication was prepared by an agency of the United States Government. Although these data were 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.
This disc is readable on any computing platform with standard DVD driver software installed. The minimum software requirements are a Web browser, a portable document format (PDF) reader, and a text editor. If you cannot fully access the information on this page, please contact USGS Information Services at infoservices@usgs.gov or 1-888-ASK-USGS.
To access the information contained on this disc, use a Web browser to open the file index.html. This report has eight sections: Home, Abbreviations, Disc Contents, Navigation Data and Maps, Subbottom Profiles, Field Activity Logs, FGDC Metadata, and Software. Links at the top and bottom of each page provide access to these sections. This report contains links to the USGS and collaborators or other resources that are only accessible if the Internet is available while viewing these documents.
This disc contains a readme (3-Kilobyte (KB) text file) document, which provides a brief description of the report; a folder containing Society of Exploration Geophysicists (SEG) Y binary data files; Geographic Information System (GIS) files used to create the trackline map; and all the Hypertext Markup Language (HTML) files, folders, and images used to produce the Web pages included in this report. The Disc Contents page contains a diagram with locations and links to all files and folders contained on this disc.
From August 13–23, 2013, the U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers (USACE) conducted geophysical surveys to investigate the geologic controls on barrier island framework and long-term sediment transport offshore of Petit Bois Island, MS. This investigation is part of a broader USGS study on Coastal Change and Transport (CCT). These surveys were funded through the Mississippi Coastal Improvements Program (MsCIP) with partial funding provided by the Northern Gulf of Mexico Ecosystem Change and Hazard Susceptibility Project. This report serves as an archive of unprocessed digital chirp subbottom data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FGDC) metadata. Gained–showing a relative increase in signal amplitude–digital images of the seismic profiles are also provided. Refer to the Abbreviations page for explanations of acronyms and abbreviations used in this report.
All chirp systems use an acoustic signal of continuously varying frequency; the EdgeTech SB-424 and 512i systems used during this survey, produce high-resolution, shallow-penetration (typically less than 50 ms) profile images of sub-seafloor stratigraphy. The towfish contains a transducer that transmits and receives acoustic energy and is typically towed 1–2 meters (m) below the sea surface. As transmitted acoustic energy intersects density boundaries, such as the seafloor or sub-surface sediment layers, some energy is reflected back toward the transducer, received, and recorded by a PC-based seismic acquisition system. This process is repeated at regular intervals (for example, 0.125 s) and returned energy is recorded for a specific duration (for example, 50 ms). In this way, a two-dimensional (2-D) vertical image of the shallow geologic structure beneath the ship's track is produced. Figure 2 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters and table 2 for trackline statistics.
The archived trace data are in standard SEG Y rev. 0 format (Barry and others, 1975); the first 3,200 bytes of the card image header are in American Standard Code for Information Interchange (ASCII) format instead of Extended Binary Coded Decimal Interchange Code (EBCDIC) format. The SEG Y files are available on the DVD version of this report or on the Web, downloadable via the USGS Coastal and Marine Geoscience Data System (http://cmgds.marine.usgs.gov). The data are also available for viewing using GeoMapApp (http://www.geomapapp.org) and Virtual Ocean (http://www.virtualocean.org) multi-platform open source software. The Web version of this archive does not contain the SEG Y trace files. To obtain the complete DVD archive, contact USGS Information Services at 1-888-ASK-USGS or infoservices@usgs.gov. The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (Cohen and Stockwell, 2010). See the How To Download SEG Y Data page for download instructions. The printable profiles provided are Graphics Interchange Format (GIF) images processed and gained using SU software and can be viewed from the Profiles page or by using the links located on the trackline maps; refer to the Software page for links to example SU processing scripts.
Detailed information about the navigation system used can be found in table 1 and the FACS logs. To view the trackline map and navigation files, and for more information about these items, see the Navigation page.
NOTE: Due to system malfunctions, subbottom data was collected using both the 512i and 424 systems.Funding for this study was provided by the USGS Coastal and Marine Geology Program. We thank R/V Tommy Munro captain Paul Beaugez and crew (University of Southern Mississippi/Gulfcoast Research Laboratory - Biloxi, MS) for their assistance in data collection and Will Pfeiffer and Nancy DeWitt for their assistance with bathymetry data processing. This document was improved by the reviews of Marci Marot and Samantha Kuzma of the USGS - St. Petersburg, Fla. and Cherokee Nation Technology Solutions, respectively.
Disc Image Credit: Descloitres, J., Moderate Resolution Imaging Spectroradiometer (MODIS) Land Rapid Response Team at the NASA Goddard Space Flight Center, 2001, Mississippi.A2001361.1640.250m.jpg. Available on-line at http://visibleearth.nasa.gov/view_rec.php?id=2364.
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 at https://dx.doi.org/10.1190/1.1440530.]
Cohen, J. K. and Stockwell, Jr. J. W., (2010), CWP/SU–Seismic Un*x Release No. 41–An open source software package for seismic research and processing, Center for Wave Phenomena, Colorado School of Mines Web page, accessed on October 15, 2014, at http://www.cwp.mines.edu/cwpcodes/.
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., accessed on October 15, 2014, at http://pubs.er.usgs.gov/usgspubs/ofr/ofr92590.
Forde, A.S., Flocks, J.G., Kindinger, J.L, Bernier, J.C., Kelso, K.W., and Wiese, D.S., 2015, Archive of Digital Chirp Subbottom Profile Data Collected During USGS Cruise 13CCT04 Offshore of Petit Bois Island, Mississippi, August 2013: U.S. Geological Survey Data Series 924, 3 DVDs, available at https://dx.doi.org/10.3133/ds924.
