U.S. Geological Survey Data Series 308

Archive of Digital Boomer and Chirp Seismic Reflection Data Collected During USGS Cruise 06FSH03 Offshore of Fort Lauderdale, Florida, September 2006

By Arnell S. Harrison,1 Shawn V. Dadisman,2 Christopher D. Reich,2 Dana S. Wiese,2 Jason W. Greenwood,2 and Peter W. Swarzenski2

1Jacobs Technology Inc., St. Petersburg, FL 33701.
2U.S. Geological Survey, St. Petersburg, FL 33701.

U.S. Department of the Interior
U.S. Geological Survey
Florida Integrated 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).


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


Page Contents:

Information Statement

System Requirements

Project Summary

Disc Organization

Getting Started

Acknowledgments

References Cited

Location Map

Information Statement

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 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 6 for Windows and Firefox 1.5 for all platforms


Project Summary

In September of 2006, the U.S. Geological Survey (USGS) conducted geophysical surveys offshore of Fort Lauderdale, FL, as part of the USGS Florida Shelf Habitat (FLaSH) Mapping Project (http://coastal.er.usgs.gov/flash). This report serves as an archive of unprocessed digital boomer and Compressed High Intensity Radar Pulse (Chirp) seismic reflection 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. Filtered and gained (a relative increase in signal amplitude has been applied) 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. 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 USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 06FSH03 tells us the data were collected in 2006 for the Florida Shelf Habitat (FLaSH) Mapping Project and the data were collected during the third field activity for that project 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 ID.

The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled on the surface waters and when discharged emits a short acoustic pulse, or shot, that propagates through the water and sediment column. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by the receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.5 s) and recorded for specific intervals of time (for example, 100 ms). The resulting profile is a two-dimensional vertical image of the shallow geologic structure beneath the ship track. Figure 1 displays the acquisition geometry for the boomer system.

All Chirp systems use a signal of continuously varying frequency; however, the Chirp system used during this survey produces a high resolution, shallow penetration (less than 50-ms) profile image beneath the seafloor. 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). Likewise, the resulting profile is a two-dimensional vertical image of the shallow geologic structure beneath the ship track. Figure 2 displays the acquisition geometry for the Chirp system. 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 2A and table 2B list trackline statistics. Scanned images of the handwritten FACS logs are also provided as PDF files.

The unprocessed seismic data are stored in SEG-Y format (Barry and others, 1975). For a detailed description of the data format, refer to the SEG-Y Format page. See the How To Download SEG-Y Data page for download instructions. The printable profiles provided here are GIF images that were filtered and 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 then 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.

NOTE: 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. This option can be found on the main Toolbar under, Tools > Options > Content > Advanced

Allow scripts to:

checkChange status bar text

Use of other browsers may result in spurious or no information given in the status window.

The printable and interactive profiles can be viewed from the Profiles page or from links located on the Survey Map page.

Detailed information about the navigation systems 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.

NOTE: Due to a system malfunction, which occurred during boomer data collection, incorrect dates were recorded to the trace headers for some of the SEG-Y files, see table 2A.


Disc Organization

The Disc Contents page is a diagram of the location of all files and folders contained on this disc and provides links to these files and folders.


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 five sections: Navigation Data and Maps, Seismic Profiles, Field Activity Logs, 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. NOTE: 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


Acknowledgments

Funding for this study was provided by the USGS Coastal and Marine Geology Program and the Department of Planning and Environmental Protection (DPEP), Broward County, FL. This document was improved by the reviews of Karen Morgan (USGS) and Jordan Sanford (CSC) at the FISC - St. Petersburg, FL.


References Cited

Barry, R.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. Also available online at http://pubs.er.usgs.gov/usgspubs/ofr/ofr92590.


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