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National Centers for Environmental Information (NCEI)

University of Texas-Institute for Geophysics


Costa Rica-Middle America Trench

Data Announcement 86-MGG-18

Approximately 2,900 km of 24-channel common depth point (CDP) seismic-reflection data for purchase from the National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)) for the eastern equatorial Pacific off Costa Rica. The data were collected by the University of Texas - Institute for Geophysics R/V IDA GREEN during three cruises in 1977 and 1978. These data have been made available by the University of Texas to NGDC (now NCEI) for public dissemination.

The seismic data were collected from a 24-channel 2,293-m array using 3/4-pound explosive charges and two Bolt Model MAG-4200 airguns having a capacity of 1.500 cu. in. per gun at a pressure of 500 psi. Data were first demultiplexed and stacked. Sections were then filtered 25-80 Hz, wave-equation migrated, trace mixed (1-31-1), and scaled with a 500-ms window. The seismic data are available as full-scale copies (scale: 2.5 in/sec). A total of 15 lines (35 sections) were processed.

The multichannel data are supplemented by single-channel sparker, 3.5- and 12-kHz precision-depth recordings, and magnetic data. The magnetic data were taken using a Proton Precession Magnetometer with the sensor towed 250 m astern at a depth of 10 m. Magnetic data sampling rate was 3 sec, digitized to 5 min and corrected to the IGRF-75 reference fields. Navigation was primarily by satellite fixes.


1. Common-Depth Point Seismic Data:
         24-fold multichannel seismic data for 15 lines, 34 sections available in plastic sepia, paper sepia, and blackline.

2. Other Geophysical Data:
         3 Reels 35-mm Microfilm (Nos. R2120, 2121, 2122) (contains 3.5- and 12-kHz depth records, single-channel sparker profiles, and magnetic analogs)

3. Merged navigation, magnetic, and bathymetric data in MGD77 format.
         1 magnetic tape (9-track, 1600 bpi, ASCII) Also available on CD-ROM.

4. 1 Navigation chart available on plastic sepia, paper sepia and blackline.