National Centers for Environmental Information (NCEI)

MULTICHANNEL SEISMIC-REFLECTION PROFILES
Cay Sal Bank Area - Southwestern Bahamas
Data from USGS Open File Report 84-346*

Data Announcement 86-MGG-01

     Approximately 550 km of multichannel seismic-reflection profiles in Santaren and Nicholas Channels, south and east of Cay Sal Bank, southwestern Bahamas, Atlantic Outer Continental Shelf, for purchase from the National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)). These data were collected in September 1979, during R/V GILLISS Cruise GS 7903, Leg 7, by the U.S. Geological Survey (USGS), in conjunction with the Rosenstiel School of Marine and Atmospheric Sciences of the University of Miami, Florida, and the Woods Hole Oceanographic Institution.

     The multichannel seismic-reflection system consisted of a 1200-m streamer and Bolt 40-cu. in. and 500-cu. in. airguns. The guns were positioned 15 m off the stern and the near-phone section was 230 m astern. The shot-point interval was 50 m. The streamer was composed of alternating active and inactive segments, each 50 m long.

     The quality of the 12-fold seismic records is excellent to 5 sec of recording time with the 500-cu. in. gun source and to 3 sec of recording time with two 40-cu. in. guns.

     Navigation was provided by the USGS's Integrated Navigation/Gravity System built around a Western Geophysical Survey and Data Management System. The Western system uses a Hewlett-Packard 21MX minicomputer and Western-designed interface circuitry to record data from six navigation sensors to calculate the accurate position of the vessel. The sensors used were: 1) Velocity output-range-range Loran, bottom-lock (pulsed) sonar, Doppler (continuous) sonar, gyroscope; and 2) position output - Navy Navigation Satellite receiver, hyperbolic Loran. The navigation is available on magnetic tape.

* Multichannel Seismic-Reflection Profiles collected aboard R/V GILLISS, Cruise GS7903, Leg 7, in Santaren and Nicholas Channels near Cay Sal, Southwestern Bahamas, by Mahlon M. Ball, Robert M. Bowles, Elizabeth L. Coward, and James E. Dodd, U.S. Geological Survey, U.S. Department of Interior, Open File Report 84-346.

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     Mention of a commercial company or product does not
     constitute an endorsement by the NOAA National Geophysical Data Center (now the National Centers for Environmental Information). Use for publicity or advertising purposes of
     information from this publication concerning proprietary
     products or the test of such products is not authorized.

DATA AVAILABLE

         1 Shot-Point Navigation magnetic tape (9-track, 1600 bpi, ASCII). This is also available on CD-ROM.

         7 Lines of multichannel seismic data available in plastic sepia, paper sepia, and blackline.

         15 Lines of velocity analyses data available on plastic sepia, paper sepia, and blackline.