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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 CD-ROM archive, contact USGS Information at (888) ASK-USGS.

In June 1999, the U.S. Geological Survey, conducted a study to test the effectiveness of high-resolution, shallow water marine seismic techniques in Lake Okeechobee, Fla. The main objective of this cruise was to ascertain if data useful to the Everglades Aquifer Storage and Recovery Project (ASR) could be acquired beneath Lake Okeechobee, Fla. using these techniques. The data indicate that shallow seismic stratigraphic maps can be produced from a survey of the entire lake. This CD-ROM serves as an archive of the unprocessed, digital, boomer seismic reflection data and all associated documentation and formal metadata. A GIF image of each seismic profile that has been filtered and gained is also provided.

This CD-ROM (Compact Disc-Read Only Memory) document was produced in accordance with the ISO 9660 CD-ROM standards and is readable on any computing platform that has standard CD-ROM driver software installed. The documentation on this CD-ROM was produced using HyperText Markup Language (HTML) utilized by the World Wide Web (WWW) and allows the user to access the information by using a WWW browser (i.e. Netscape or Internet Explorer). To access the information contained on this disc open the file index.htm at the top-level of this disc with your WWW browser. This report also contains WWW links to USGS collaborators and other agencies. These links are only accessible if access to the Internet is also available while viewing the CD-ROM.

The archived boomer single-channel, seismic reflection data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded for processing with Unix or Linux public-domain software such as Seismic Unix (SU) (http://www.cwp.mines.edu/cwpcodes/). 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 CD-ROM archive, contact USGS Information at (888) ASK-USGS. Examples of SU processing scripts are provided in the boom.tar file located in the SEISUNIX subfolder in the SOFTWARE folder at the top level of this CD-ROM. In-house (USGS) DOS and Microsoft Windows compatible software for viewing SEG-Y headers, DUMPSEGY.EXE (Zihlman, 1992) is provided in the USGS_EXE subfolder of the SOFTWARE folder located at the top level of the CD-ROM. The processed boomer profiles, reference maps, and logbooks (all GIF images) may also be viewed with your WWW browser.

This report consists of two-dimensional marine seismic reflection profile data from Lake Okeechobee, Fla., that were acquired in June of 1999, aboard the R/V G. K. Gilbert. These data are available in a variety of formats, including binary, ASCII and GIF images. Binary data are in Society of Exploration Geophysicists (SEG) SEG-Y format and may be downloaded for further processing or display. 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 CD-ROM archive, contact USGS Information at (888) ASK-USGS.

Purpose:

Marine seismic reflection data are used to image and map sedimentary and structural features of the seafloor and subsurface. The main objective of this cruise was to ascertain if data useful to the Everglades Aquifer Storage and Recovery Project could be acquired using seismic techniques. These data proved to be useful in mapping the extent and thickness of shallow sedimentary units beneath Lake Okeechobee, Fla., and in assessing other submarine geologic characteristics and features.

Supplemental Information:

Seismic reflection profiles are acquired by means of an acoustic source (usually generated electronically), and a hydrophone or hydrophone array. Both elements are typically towed in the water behind a survey vessel. The sound source emits a short acoustic pulse, which propagates through the water and sediment columns. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), and detected at the hydrophone. This process is repeated at intervals ranging between 100 ms and 1 s depending on the source type. In this way a two-dimensional image of the geologic structure beneath the ship track is constructed.

Seismic data are stored in SEG-Y format, which is a standard digital format that can be read and manipulated by most seismic-processing software packages. The SEG-Y file format includes a 3200-byte descriptive header that contains detailed information regarding the data acquisition and processing parameters. All data presented here are stored in SEG-Y, integer, Motorola format. The SEG-Y formatted trace data files are located in the SEGY folder at the top level of this disc, and have a .tra extension. Additional recording parameters for each seismic data file can also be found in the .par file associated with each .tra file. However, the .par files and the cent_rmc.pln file are only needed to replay the data with Triton Elics Delph Seismic software. 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 CD-ROM archive, contact USGS Information at (888) ASK-USGS.

The seismic energy source employed here was a boomer transducer towed on a sled at the lake surface providing 200 joules per shot. The reflected energy was received by an Innovative Transducer Inc. (ITI) solid core streamer and recorded by PC-based Triton Elics Delph Seismic acquisition software. The ITI streamer contains 10 hydrophones evenly spaced over 6 meters however only data received by elements 5-8 where summed, resulting in a higher signal to noise ratio for the data. The streamer was positioned parallel to the boomer sled and laterally separated from it by 7 m. The sled was towed 20 m behind the Global Positioning System (GPS) antennae. The sample frequency of the data was 16000 Hz and the total record length for tracklines oke699_1 to oke699_7 was 200 ms, and 300 ms for tracklines oke699_8 to oke69911. The fire rate was every 0.5 s, which resulted in a shot spacing of about 1 m based on survey speeds of 3.5-4 knots. GPS navigation was provided by a Trimble Centurian P-Code receiver directly fed to the acquisition system every 1 s. The shotpoint navigation provided in this report has not been corrected to reflect the 20 m offset of the source to the GPS antenna. The horizontal accuracy of the navigation data was within 31 m.

The navigation data are stored as flat ASCII files. The raw navigation files were generated by the Delph Seismic Software for each trackline and provides the following information for each unique position fix, all separated by commas: shotpoint number, longitude, latitude, heading, speed, date, and Greenwich Mean Time (GMT). The edited navigation file contains all the unique fixes for each trackline with spurious points removed. A separate file containing edited navigation for every 500th shotpoint interval is also provided. Both the edited navigation and the 500 shotpoint navigation files contain six fields separated by commas: shotpoint number, date, GMT, longitude, latitude, and the trackline number. This navigation data can be used to plot trackline maps of the seismic profiles at any scale or map projection desired. The trackline map provided on this disc is a Mercator projection and was created with ESRI's GIS software ArcView 3.2. The map was then exported to Adobe Illustrator and saved as a GIF image. This GIF image is viewable with your WWW browser.

INDEX.HTM: The home page for viewing this report using a World Wide Web (WWW) browser.

README.TXT: A brief discription of this Open File Report in ASCII text format.

DISCLAIM.TXT: The ASCII text file stating the USGS disclaimer for this report.

METADATA.TXT: The formal FDGC metadata for the seismic data in ASCII text format.

FACS Folder: Contains the Field Activity Collection System sheets documenting the cruise overview, crew, equipment, and trackline information in Microsoft Excel format.

HTML Folder: Contains the necessary HTML files to allow the user access to the CD-ROM via any WWW browser.

IMAGES Folder: Contains GIF and JPEG images that are used by HTML hyperlinks.

LOGBOOKS Folder: Contains the scanned images of the observers' handwritten logbooks in both PDF format and as GIF images.

MAPS Folder: Contains the GIF image of the trackline map.

RAWNAV Subfolder: Contains the RAWNAV and SHOTNAV folders.

RAWNAV Folder: Contains the raw unedited p-code GPS navigation files in ASCII text format.

SHOTNAV Folder: Contains the edited shot navigation data that was extracted from the SEG-Y headers and navigation fixes for every 500th shotpoint interval, both in ASCII text format (shot.txt & 500shot.txt).

SEGY Folder: Contains the unprocessed, digital, boomer, single-channel, seismic reflection data for each trackline in SEG-Y format.

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 CD-ROM archive, contact USGS Information at (888) ASK-USGS.

SEISIMAG Folder: Contains the GIF images of the boomer seismic profiles generated with Seismic Unix.

SOFTWARE Folder: Contains the SEISUNIX and USGS_EXE folders.

SEISUNIX Folder: Contains the Unix tar file (boom.tar), which contains example Seismic Unix scripts used to process and plot the boomer reflection data and extract shot navigation from the SEG-Y headers.

USGS_EXE Folder: Contains the DOS program DUMPSEGY.EXE for viewing SEG-Y headers and the associated reference documentation.

This Compact Disc-Read Only Memory (CD-ROM) publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Although all data published on this CD-ROM have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data, software, or related materials.

We thank Keith Ludwig, captain of the R/V G. K. Gilbert for his help in the data collection; Dave Foster and Jenna Hill, of the USGS Seafloor Mapping Group in Woods Hole, Mass., for providing examples of their archives; Jon Childs with the USGS in Menlo Park, Calif., who provided examples of his formal metadata; and Trent Faust and Rob Wertz, at the USGS in St. Petersburg, Fla., for their help with the web design and technical layout of the CD-ROM.

Barry, R.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats, Geophysics, v. 40, p. 344-352.

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.

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