Find U.S. Geological Survey Coastal and Marine Geology Program Web Information

Read Me

This DVD was produced in accordance with UDF (Universal Disc Format) standard for DVD . It is readable on any computing platform that has standard DVD driver software installed. The documentation on this DVD was produced using the Hyper Text Markup Language (HTML) utilized by the World Wide Web (WWW ) and allows the user access to the information contained on this disc by using a WWW browser (i.e. Netscape or Internet Explorer). 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 DVD .

About the CD-ROM

The CD-ROM included with this report contains GIS information for use with ESRI 's GIS software packages. It was produced in accordance with ISO9660 standards for CD-ROM.

Note: The web version of this archive does not contain the GIS files. These files are very large and would require long download times. To obtain the complete archive, contact USGS Information at (888) ASK-USGS.

How to Access The Data

To view the HTML formatted version of this report double-click on the file index.htm at the top level of this DVD . Also located at the top level of this disc are the text files readme.txt, metadata.txt, and disclaimer.txt, all of which will give you more information about the contents of this DVD . The CD-ROM contains an ARC Folder which has a Themes subfolder, containing shapefiles for use with ESRI software, and an ArcView 3.2 project keys.apr.

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 (888) ASK-USGS.

In October 1997, the U.S. Geological Survey, conducted a study to image the surficial and near surface features of the upper and middle Florida Keys. The main objective of this cruise was to fill a major gap in the seismic data record. No seismic data had been collected in this area during a 20 year study of the reef track. This DVD serves as an archive of the unprocessed, digital, boomer seismic reflection data and all associated documentation and formal metadata. A filtered and gained JPG image of each seismic profile is provided on the DVD . The CD-ROM contains GIS information for use with ESRI 's ArcExplorer 2.0, 4.0, ArcView 3.x and ArcGIS 8.1.

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 public domain software such as Seismic Unix (SU) (http://www.cwp.mines.edu/cwpcodes/). 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 DVD . 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 DVD . The processed boomer profiles, reference maps, and logbooks (JPG and GIF images) may be viewed with your WWW browser.

This report consists of two-dimensional marine seismic reflection profile data from the upper and middle Florida Keys. The area of operations extended from just north of Molasses Reef off north Key Largo to the eastern boundary of Looe Key National Marine Sanctuary. These data were acquired in October and November of 1997, aboard the Charter Research Vessel, Captain's Lady. The data are available in a variety of formats, including binary, ASCII, HTML , Shapefiles, JPG and GIF images. Binary data are stored in Society of Exploration Geophysicists (SEG) SEG-Y format and can be downloaded for further processing or display.

Purpose:

Marine seismic reflection data are used to image and map sedimentary and structural features of the seafloor and subsurface. These data are useful in mapping the extent and thickness of shallow sedimentary units in the upper and middle Keys, and in assessing other submarine geologic characteristics and features. The main objective of this cruise was to fill a major gap in the seismic data record. Seismic data had not been collected in this area during a 20 year study of the reef track.

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 should contain detailed information regarding the data acquisition and processing parameters. All data presented on this DVD 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 plg_gga.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 DVD archive, contact USGS Information at (888) ASK-USGS.

The seismic source employed here was a boomer transducer towed on a sled at the sea surface providing 100 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 GPS antennae. The sample frequency of the data was 12000 Hz and the total record length was 100 ms. The fire rate was every 0.25 sec which resulted in a shot spacing of about .5 m based on survey speeds of 3.5-4 knots.

GPS navigation was fed to the acquisition system every second by the navigation system, a Rockwell navigation receiver. The accuracy of this receiver is within 100 m, however the data required some editing. A filter was designed to remove spurious data values and these edited results were used to generate the trackline maps provided on this DVD . These maps were generated with ArcView 3.2 as geographic projections, and are provided in this report as GIF images. A position for every 500th shotpoint, and the start and end of each trackline are also provided for easy registering of the data. However, the shotpoint navigation has not been corrected to reflect the 20 m offset between the source and the GPS antenna. All navigation files are stored as flat ASCII text files. The raw navigation files, which did not have the year or julian day written to the record, are located in the RAWNAV subfolder of the NAV folder located at the top level of the DVD . The edited navigation files, which have year and julian day manually entered into the records, are stored in the EDITNAV subfolder of the NAV folder, and the 500 shotpoint interval files are stored in the SHOTNAV subfolder of the NAV folder. They also have the year and julian day manually entered into each record.

On the CD-ROM included with this report are GIS files created with ESRI 's ArcView 3.2, displaying the shotpoint information for each seismic trackline. These files are compatible with either ArcView 3.x (UNIX or WINDOWS) or ArcGIS 8.1 (WINDOWS). The files can also be viewed by using Windows compatible public domain software ArcExplorer 2.0, and Java Edition 4.0. To download a free copy of ArcExplorer go to the ESRI website (http://www.esri.com/software/arcexplorer/).

Index.htm - The home page for viewing this report using a World Wide Web (WWW ) browser.

Readme.txt - A brief description 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 FGDC 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 operation information in Rich Text format.

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

IMAGES Folder: Contains GIF images that are used by HTML hotlinks.

LOGBOOKS Folder: Contains the scanned images of the handwritten observers logbooks as GIF images.

MAPS Folder: Contains the GIF images of the trackline maps.

NAV Folder: Contains the RAWNAV, SHOTNAV and EDITNAV subfolders.

RAWNAV Subfolder: Contains the raw, unedited Delph Seismic navigation files in ASCII text format.

SHOTNAV Subfolder: Contains the navigation fixes for every 500th shotpoint interval extracted from the SEG-Y headers, in ASCII text format.

EDITNAV Subfolder: Contains the edited Delph Seismic navigation files in ASCII text format.

SEGY Folder: Contains the unprocessed, digital, boomer, single-channel, seismic reflection data for the tracklines 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 DVD archive, contact USGS Information at (888) ASK-USGS.

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

SOFTWARE Folder: Contains the SEISUNIX and USGS_EXE subfolders.

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

CD-ROM CONTENTS

Note: The web version of this archive does not contain the GIS files. These files are very large and would require long download times. To obtain the complete archive, contact USGS Information at (888) ASK-USGS.

ARC Folder: Contains the subfolder THEMES and the ArcView 3.2 project file 97KEY01.apr.

THEMES Subfolder: Contains the shapefiles used to create the trackline maps in ArcView 3.2. Which may also be used with ArcExplorer and ArcGIS.

This Digital Versatile Disc (DVD ) and 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 DVD and 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.

The USGS Coastal and Marine Geology Program (CMGP) provided the funding for research east and northeast of the Looe Key National Marine Sanctuary (LKNMS), to Molasses Reef off the upper Keys. Bill Causey, Superintendent of the Florida Keys National Marine Sanctuary (FKNMS), and Sanctuary Rangers (Florida Department of National Resources, Bureau of Environmental Land Management) are thanked for their cooperation during the field survey. Personnel from the USGS in St. Petersburg, Fla., and the National Oceanic and Atmospheric Administration's (NOAA) FKNMS conducted most of the project in the middle and upper Keys as a cooperative study under permit FKNMS-29-97. We thank Captain Stephen R. Cawthon who led Captain's Lady on her final voyage as a research vessel in 1997, for assistance in data collection. Appreciation is extended to numerous colleagues for their field assistance. All are acknowledged by name in publications resulting from each part of the project. Stanley D. Locker, University of South Florida St. Petersburg campus, assisted in numerical data conversion to compensate for the rapid speed-of-sound return in shallow water. James G. Flocks, USGS geologist, produced the seismic-profile trackline navigation and data map panels for contouring. Digital cartographer Lance E. Thornton digitized final contours into the ARC/INFO GIS program for the bedrock and isopach plates. Shawn V. Dadisman, helped in the processing and production of the GIF image profiles and thumbnails for this archive. Jeff Dismukes provided scripts for editing and reformatting the navigation data for use with ESRI 's ArcView 3.2. The authors greatly appreciate the efforts of these colleagues.

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.