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Archive of Digital Chirp Sub-bottom Profile Data Collected During USGS Cruise 09CCT01 Offshore of Sabine Pass and Galveston, Texas, March 2009

By Arnell S. Forde,¹ Shawn V. Dadisman,¹ James G. Flocks,¹ Timothy M. Dellapenna,² Jordan M. Sanford,¹ and Dana S. Wiese¹

¹U.S. Geological Survey, St. Petersburg, FL 33701.
²Texas A&M University at Galveston, Galveston, TX 77553.

U.S. Department of the Interior
U.S. Geological Survey
St. Petersburg Science Center - St. Petersburg

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 (Disc 1 of 5): Information Statement System Requirements Project Summary Disc Organization Getting Started Acknowledgments References Cited

Information Statement

This Digital Versatile Disc (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.

System Requirements

This disc is readable on any computing platform that has standard DVD driver software installed. The minimum software requirements are a Web browser, Adobe 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. NOTE: The only supported Web browsers that properly display all features of the interactive profiles are Internet Explorer 8 for Windows and Firefox 3.6 or greater for all platforms

Project Summary

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 512i Chirp sub-bottom profile data, trackline maps, navigation files, Geographic Information System (GIS) files, Field Activity Collection System (FACS) logs, observer's logbook, and formal Federal Geographic Data Committee (FGDC) metadata. Gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansion of acronyms and abbreviations used in this report.

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 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 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 field activity identification (ID).

All Chirp systems use a signal of continuously varying frequency; the Chirp system used during this survey produces a high resolution, shallow penetration profile image beneath the seafloor. 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 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. Figure 1 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters. See the digital FACS equipment log (12-KB PDF) for details about the acquisition equipment used. Table 2 lists trackline statistics. Scanned images of the handwritten FACS logs and handwritten science logbook (397-KB PDF) are also provided.

The unprocessed seismic data are stored in SEG-Y integer format (Barry and others, 1975). See the How To Download SEG-Y Data page for download instructions. Note: The web version of this archive does not contain the SEG-Y trace files. These files are very large and would require extremely long download times. To obtain the complete DVD archive, contact USGS Information at 1-888-ASK-USGS or infoservices@usgs.gov. The printable profiles provided here are GIF images that were gained using Seismic Unix software. Refer to the Software page for details about the processing and examples of the processing scripts. The processed SEG-Y data were exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce an interactive version of the profile that allows 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.

The printable and interactive profiles can be viewed from the Profiles page or from links on the trackline maps. Detailed information about the navigation system used can be found in table 1 and the FACS equipment log (12-KB PDF). To view the trackline maps and navigation files, and for more information about these items, see the Navigation page.

Disc Organization

The Disc Contents page is a diagram with links to the locations of all files and folders contained on this disc; all discs in the set are identical except for the SEG-Y files they contain. Disc 1 contains SEG-Y files for lines 09c01 through 09c19, disc 2 contains SEG-Y files for lines 09c20 through 09c37, disc 3 contains SEG-Y files for lines 09c38 through 09c53, disc 4 contains SEG-Y files for lines 09c54 through 09c67, and disc 5 contains SEG-Y files for lines 09c68 through 09c80.

Getting Started

To access the information contained on this disc, use a Web browser to open the file index.html. This report is divided into seven sections: Acronyms and Abbreviations, Disc Contents, Navigation Data and Maps, Seismic 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 accessible only if access to the Internet is available while viewing these documents.

Acknowledgments

Funding and (or) support for this study was provided by the USGS Coastal and Marine Geology Program and Texas A&M University. 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 Woods Hole Coastal and Marine Science Center - Woods Hole, MA) and Julie Bernier (USGS St. Petersburg Coastal and Marine Science Center - St. Petersburg, FL).

References Cited

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. (284-KB PDF)

Cohen, J.K., and Stockwell, J.W., Jr., 2005, CWP/SU: Seismic Unix Release 41: An open source software package for seismic research and processing: Center for Wave Phenomena, Colorado School of Mines. Also available on-line 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. Also available on-line at http://pubs.er.usgs.gov/usgspubs/ofr/ofr92590.