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National Geophysical Data Center

University of Texas-Institute for Geophysics

Offshore Brazil

Data Announcement 83-MGG-09

Approximately 2,072-line km of 3- and 12-fold multichannel common depth point (CDP) seismic data are now available for offshore Brazil. The data were collected by the University of Texas Institute for Geophysics during 2 cruises of Research Vessel FRED M. MOORE in July 1979 as part of its Southwest Atlantic IPOD (International Phase of Ocean Drilling) Site Survey. Data were gathered to define the geologic and geophysical setting for proposed IPOD drilling sites.

Data acquisition during the first cruise originated in the Hunter Channel area and approximately 1,035-line km of 6-trace 3-fold data (23 lines) are available. A 600-m streamer was used as the receiver and the sound source consisted of an array of three Bolt (R) airguns firing simultaneously at 500 psi. On some lines, 5/8- lb maxipulse charges served as the high-resolution profiling source. The airgun lines were recorded as filtered multiplexed data on a DFS-4 system at a 4-ms sampling rate and the maxipulse data at a 2-ms rate. The multichannel data were supplemented by continuous 12-kHz precision depth recordings. Total field magnetic intensity measurements were made with a Varian(R) proton precession magnetometer. The CDP seismic data are available as full-scale copies (Scale: 2.5 in/sec). Other geophysical data are available on 35-mm microfilm or magnetic tape.

Data acquired during the second cruise in the northern Argentine Basin area consists of approximately 1,035-line km of 24-trace 12- fold data (41 lines). A 1,200-m streamer was used as the receiver for both the airgun and the maxipulse lines. Velocity analyses for the CDP seismic data collected during this part of the cruise are available on 1 reel of 35-mm microfilm. The University of Texas has provided these data to the National Geophysical Data Center (NGDC) for public dissemination.

1. Common Depth Point Seismic Data: 3- and 12-fold data for 64 lines (full-scale). Available in plastic sepia, paper sepia, and blackline.

2. Other Geophysical Data: includes sparker, profiler magnetics on 2 rolls of microfilm (Nos. 1845 and 1846). Available in 35-mm microfilm.

3. Velocity Analyses - 1 roll of microfilm (No. 1847 - WSA lines only). Available in 35-mm microfilm.

4. Track Charts (scale: 4 in/degree) available in plastic sepia, paper sepia, and blackline.

Merged navigation, magnetics and bathymetry data are available on 1 magnetic tape, 9-track, 1,600 bpi, and ASCII. This is also available on CD-ROM.

Please contact NGDC for prices.