Open-File Report 03-274
ARCHIVE OF BOOMER SEISMIC REFLECTION DATA
COLLECTED DURING USGS CRUISES 01SCC01 AND
01SCC02, TIMBALIER BAY AND OFFSHORE EAST
TIMBALIER ISLAND, LOUISIANA, JUNE - AUGUST 2001
by Karynna Calderon, Shawn V. Dadisman, James G. Flocks, Jack L. Kindinger, and Dana S. Wiese
U.S. Geological Survey Open-File Report 03-274
In June, July, and August of 2001, the U.S. Geological Survey (USGS), in cooperation with the University of New Orleans (UNO), the U.S. Army Corps of Engineers, and the Louisiana Department of Natural Resources, conducted a shallow geophysical and sediment core survey of Timbalier Bay and the Gulf of Mexico offshore East Timbalier Island, Louisiana. This report serves as an archive of unprocessed digital seismic reflection data, trackline navigation files, trackline navigation maps, observers' logbooks, Geographic Information Systems (GIS) information, and formal Federal Geographic Data Committee (FGDC) metadata. In addition, a filtered and gained digital Graphics Interchange Format (GIF) image of each seismic profile is provided. Please see Kulp and others (2002), Flocks and others (2003), and Kulp and others (in prep.) for further information about the sediment cores collected and the geophysical results. For convenience, a list of acronyms and abbreviations frequently used in this report is also included.
This Digital Versatile Disc (DVD) document is readable on any computing platform that has standard DVD driver software installed. Documentation on this DVD was produced using Hyper Text Markup Language (HTML) utilized by the World Wide Web (WWW) and allows the user to access the information using a web browser (i.e. Netscape, Internet Explorer). To access the information contained on this disc, open the file 'index.htm' located at the top level of the disc using a web browser. This report also contains WWW links to USGS collaborators and other agencies. These links are only accessible if access to the Internet is available while viewing this DVD.
The archived boomer seismic reflection data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry et al., 1975) and may be downloaded for processing with public domain software such as Seismic Unix (SU), currently located at http://www.cwp.mines.edu/cwpcodes/index.html. Examples of SU processing scripts are provided in the BOOM.tar file located in the SU subfolder of the SOFTWARE folder located at the top level of this disc. In-house (USGS) DOS and Microsoft Windows compatible software for viewing SEG-Y headersDUMPSEGY.EXE (Zihlman, 1992)is provided in the USGS subfolder of the SOFTWARE folder. Processed profile images, trackline navigation maps, logbooks, and formal metadata may be viewed with a web browser.
This archive consists of two-dimensional marine seismic reflection profile data collected in Timbalier Bay and in the Gulf of Mexico offshore East Timbalier Island, Louisiana. These data were acquired June 30 - July 9 (01SCC01) and August 1 - 18 (01SCC02), 2001, aboard the R/V G.K. Gilbert and a UNO 21-foot Proline. Included here are data in a variety of formats including binary, American Standard Code for Information Interchange (ASCII), HTML, Portable Document Format (PDF), Rich Text Format (RTF), GIF and Joint Photographic Experts Group (JPEG) images, and shapefiles. Binary data are in Society of Exploration Geophysicists (SEG) SEG-Y format and may be downloaded for further processing or display. Reference maps and GIF images of the profiles may be viewed with a web browser. The GIS map documents provided were created with Environmental Systems Research Institute (ESRI) GIS software ArcView 3.2 and 8.1.
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 stratigraphy and in assessing other submarine geologic characteristics and features. These data were collected as part of a Louisiana Sand Resources Study done in collaboration with the University of New Orleans, the U.S. Army Corps of Engineers, and the Louisiana Department of Natural Resources. This study is part of the USGS Subsidence and Coastal Change (SCC) Project.
The USGS Center for Coastal and Watershed Studies team in St. Petersburg, Florida, assigns a unique identifier to all seismic data collected during each cruise or field activity. The method used to assign the identifier for the activity is as follows: YYPPP##, where YY stands for the last 2 digits of the year in which the fieldwork is conducted, PPP is a 3-letter abbreviation for the project the data are collected for, and ## is a 2-digit event tag that represents a discreet leg or time period of fieldwork. Here, for example, 01SCC01 tells us the data were collected in 2001 for the Subsidence and Coastal Change Project and that the data were collected during the first field activity for that project in that calendar year. The naming convention the center uses for each seismic line is as follows: yye###a, where yy is the last 2 digits of the year in which the data were collected, e is a 1-letter abbreviation for the equipment type (i.e., c for chirp and b for boomer), ### is a 3-digit number representing a specific track, and a is a 1-letter abbreviation representing the section of a line if recording was prematurely terminated or rerun for quality or acquisition problems.
Seismic reflection profiles are acquired by means of an acoustic source (usually generated electronically) and hydrophone or receiver arrays. Both elements are typically towed in the water behind a survey vessel. The sound source 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) and detected at the receiver. This process is repeated at intervals ranging between 100 milliseconds (ms) and 1 second (s) depending on the seismic source employed. In this way, a two-dimensional vertical image of the geologic structure beneath the ship track can be interpreted.
The boomer energy source consists of capacitors that are charged to a high voltage and then discharged through a transducer in the water. The frequency range of the source is between 300 and 3,000 hertz (Hz). The transducer was towed on a sled at the sea surface providing 100 joules (J) per shot for lines 01b001-01b046 and 01b082-01b093 and 200 J per shot for lines 01b047-01b080. The reflected energy was received by a streamer and recorded by PC-based Triton Elics Delph Seismic acquisition software. In an attempt to resolve unknown acquisition problems, streamers were switched throughout the first cruise between Innovative Technologies, Inc. (ITI) ST5 and SN Technologies NexGen streamers. Only the NexGen streamer was used for the second cruise. Both streamers contain 10 hydrophones. These are evenly spaced every 2 feet (0.6 m) on the ITI streamer and every 2 m on the NexGen streamer. Only data received by elements 4-7 were summed for lines 01b001-01b028, by elements 5 and 6 for lines 01b029-01b089, and by elements 7 and 8 for lines 01b091-01b093. The streamer was positioned parallel to the boomer sled and laterally separated from it by about 7 m for lines 01b001-01b080, which were collected on the R/V G.K. Gilbert, and by about 4 m for lines 01b082-01b093, which were collected on a 21-foot Proline. The sled was towed about 20 m behind the Global Positioning System (GPS) antenna on the R/V G.K. Gilbert and about 12 m behind on the Proline. No correction for this offset has been made. The sample frequency of the data was 12 kilohertz (kHz). All tracklines were recorded to 100 ms. Based on survey speeds of 3.5-4 knots and a shot rate of every 0.5 s, the shot spacing was about 1 m.
Seismic data were 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 3,200-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 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 and .pln files included are only needed to process or display the data with Triton Elics Delph Seismic software. These files are all stored in the SEGY folder located at the top level of this disc. No SEG-Y data exists for tracklines 01b002 and 01b081.
For lines 01b001-01b080, Differential GPS (DGPS) navigation was provided by a CSI DGPS Max WAAS/Beacon DGPS receiver, whose accuracy is within 5 m. The DGPS string was fed to a navigation computer running Hypack software, which converted the data to Zone 15 Universal Transverse Mercator (UTM) coordinates. The navigation was then fed to the Delph Seismic acquisition system approximately every second and recorded in the SEG-Y headers. For lines 01b082-01b093, GPS navigation was provided by a Trimble Centurian P-Code receiver, whose accuracy is within about 100 m. The GPS string was fed directly to the acquisition system approximately every second in latitude and longitude and recorded in the SEG-Y headers. Both UTMs and latitude and longitude are provided for all lines. The data required some editing to remove spurious data values. The edited results were used to generate the trackline maps presented here. The navigation data have not been corrected to reflect the offset between the shotpoint and the GPS antenna. Position fixes for every 500 shots and for the start of lines are also provided as an aid for registering of the data after plotting. All navigation files are stored as flat ASCII text files within the NAV folder located at the top level of this disc. Raw navigation files are stored in the RAWNAV subfolder, edited navigation files are stored in the EDITNAV subfolder, and 500-shot interval files are stored in the SHOTNAV subfolder.
The trackline maps provided in this archive are unprojected, set in geographic coordinates, North American Datum 1983 (NAD83). They were created using ESRI GIS software ArcView 3.2 and 8.1, exported to Adobe Illustrator for further editing, and saved for the web in JPEG format. These JPEG images are viewable with a web browser and can be found in the MAPS folder located at the top level of this disc. Also included on this disc are the ArcView map documents and shapefiles used to create the trackline maps presented here. These can be found in the ARC subfolder of the SOFTWARE folder located at the top level of this disc. The map documents are compatible with ArcGIS 8.x (Windows). The shapefiles can also be viewed using ArcView 3.x or public domain software ArcExplorer 2.0 (Windows) and 4.0 (Windows, Unix, Linux), which can currently be downloaded from the ESRI website at http://www.esri.com/software/arcexplorer/index.html.
Field Activity Collection System (FACS) logs are available in both HTML and Rich Text Format. They can be found in the FACS folder located at the top level of this disc. Scanned versions of the handwritten logbooks are provided as PDF files which can be found in the LOGBOOKS folder located at the top level of this disc.
Also included on this disc are example Seismic Unix (SU) 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. These images can then be displayed using a variety of shareware programs such as ImageMagick (Unix, Linux) or a web browser. The example scripts are included in the BOOM.tar file which can be found in the SU subfolder of the SOFTWARE folder located at the top level of this disc.
INDEX.htm: a home page for viewing this report using a web browser
DISCLAIM.rtf: the USGS disclaimer for this report in Rich Text Format
METADATA.rtf: formal FGDC metadata for the seismic reflection data and associated shotpoint navigation maps in Rich Text Format
README.rtf: a Rich Text Format version of this page
FACS Folder: contains the 01SCC01 and 01SCC02 subfolders
HTML Folder: contains all HTML documents used in this report and JPEG images used by the HTML hyperlinks
LOGBOOKS Folder: contains CREW.pdf, a PDF file with scanned images of the handwritten crew logbooks filled out by James G. Flocks, and FACS.pdf, a PDF file with scanned images of the handwritten FACS logbooks filled out by Dana S. Wiese
MAPS Folder: contains the trackline maps as JPEG images
NAV Folder: contains the EDITNAV, RAWNAV, and SHOTNAVsubfolders
PROFILES Folder: contains the 01SCC01 and 01SCC02 subfolders
SEGY Folder: contains the 01SCC01 and 01SCC02 subfolders
SOFTWARE Folder: contains the ARC, SU, and USGS subfolders
This Digital Versatile Disc (DVD) 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 have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or 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 or related materials.
Funding and/or support for this study were provided by the Coastal and Marine Geology Program (CMGP) of the USGS, the University of New Orleans, the U.S. Army Corps of Engineers, and the Louisiana Department of Natural Resources. We thank R/V G.K. Gilbert Captains Dave Bennett of Eckerd College in St. Petersburg, Florida, and Keith A. Ludwig and Richard W. Young of the USGS in St. Petersburg, Florida, for their assistance in data collection. We also thank reviewers Thomas J. Smith and Kimberly K. Yates of the USGS in St. Petersburg, Florida, whose comments improved this document.
Barry, R.M., Cavers, D.A., and Kneale, C.W., 1975, Recommended standards for digital tape formats: Geophysics, v. 40, p. 344-352.
Flocks, J., Kulp, M., and Kindinger, J., 2003, Identifying offshore sand resources to restore Louisiana's barrier shorelines: Coastal Sediments 2003 Conference, Proceedings, 13 p.
Kulp, M., Penland, S., Flocks, J., and Kindinger, J., 2002, Regional geology, coastal processes, and sand resources in the vicinity of East Timbalier Island: Louisiana Department of Natural Resources Technical Report, 101 p.
Kulp, M., Penland, S., Flocks, J., and Kindinger, J., in prep., Regional geology, coastal processes, and sand resources in the vicinity of East Timbalier Island: U.S. Geological Survey Open-File Report, 101 p.
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.