Archive of Digital Boomer Seismic Reflection Data Collected Offshore East-Central Florida during USGS Cruises 96FGS01 and 97FGS01 in November of 1996 and May of 1997
In November of 1996 and May of 1997, the U.S. Geological Survey (USGS), in cooperation with the Florida Geological Survey (FGS), conducted geophysical surveys of the shallow geologic framework of the continental shelf offshore east-central Florida from Cape Canaveral to Sebastian Inlet. This report serves as an archive of unprocessed digital boomer seismic reflection data, navigation files, trackline maps, GIS files, FACS logs, and FGDC metadata. Filtered and gained digital images of the seismic profiles are also provided. The archived trace data are in standard Society of Exploration Geophysicists SEG Y format (rev. 0) (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.
These data are also available for viewing using GeoMapApp (
http://www.geomapapp.org/) and Virtual Ocean (
http://www.virtualocean.org/) multi-platform open source software. In addition, the SEG Y files can also be downloaded from the USGS Coastal and Marine Geoscience Data System (
http://cmgds.marine.usgs.gov).
The U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (SPCMSC) in Florida assigns a unique identifier to each cruise or field activity. For example, 96FGS01 tells us the data were collected in 1996 for the Florida Geological Survey (FGS) cooperative agreement 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 cruise or field activity ID. The naming convention used for each seismic line is as follows: yy_e##_a, where 'yy' are the last two digits of the year in which the data were collected, 'e' is a one-letter abbreviation for the equipment type (for example, b for boomer), '##' is a two-digit number representing a specific track, and 'a' is a letter representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems.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 at the sea surface 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 a receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.25 seconds) and recorded for specific intervals of time (for example, 100 milliseconds). In this way, a two-dimensional vertical image of the shallow geologic structure beneath the ship track is produced.A Huntec power supply provided 60-135 joules per shot for 96FGS01 and 480 joules per shot for 97FGS01. Reflected energy was received by an Innovative Transducers, Inc. (ITI) ST-5 streamer and recorded by Delph Seismic and DelphWin acquisition software. The streamer, which contains 10 hydrophones evenly spaced over a length of 6 meters (every 2 feet), was positioned parallel to the boomer sled and laterally separated from it by about 7 meters. Refer to figure 1 included with this archive for a diagram of acquisition geometry. For both cruises, the sample frequency of the data is 16 kilohertz, and record length is 100 milliseconds. Based on survey speeds of 3.5 - 4 knots and a shot rate of every 0.25 seconds, shot spacing is about every 0.5 meters.The unprocessed seismic data are stored in SEG Y (rev. 0), integer, Motorola format, which is a standard digital format that can be read and manipulated by all seismic processing software packages (Barry and others, 1975). The SEG Y files may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU) (Cohen and Stockwell, 2005). See the How To Download SEG Y Data page for download instructions. The SEG Y formatted trace files have a .tra extension. Additional recording parameters for each trace file can also be found in the .par file associated with each .tra file. However, the .par and .pln files included here are only needed to process or display the data with Delph Seismic software. Also provided are example Seismic Unix scripts that allow the user to strip off navigation fixes from the SEG Y headers, along with a fix for every 500 shots, and produce a filtered and gained GIF image of each profile. The printable profiles provided here are GIF images that were filtered and gained using SU software. Refer to the Software page for links to example SU processing scripts and USGS software for viewing the SEG Y files (Zihlman, 1992). The processed SEG Y data were exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce geospatial versions of the profiles that allow the user to obtain a geographic location and depth from the profile for a curser position. This information is displayed in the status bar of the browser. The SEG Y files for both cruises do not fit on one disc, so they have been distributed onto two DVDs. Disc 1 contains data for all 96FGS01 lines and 97FGS01 lines sb_a1_a - sb_b25_b. Disc 2 contains 97FGS01 lines sb_b26_a - t1_sb. The 97FGS01 lines are grouped by alphabetical/numerical order, not the order in which they were collected. NOTE: The only supported Web browsers that properly display all features of the geospatial profiles are Internet Explorer 8 or greater for Windows and Firefox 3.6 or greater for all platforms. For both browsers, the status bar and JavaScript must be enabled. Firefox also requires "Change status bar text" to be checked under Advanced JavaScript Options. If using Internet Explorer 8, you must disable scripts/Active X controls. To do this, right click the information bar (found at the top of the page), left click "Allow Blocked Content...", and then select "Yes." Use of other browsers may result in spurious or no information given in the status window. Firefox may be downloaded at
http://www.mozilla.org/products/firefox.
