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National Centers for Environmental Information (NCEI)

Aleutian Arc and Trench, Alaska
USGS Open File Reports 88-502 and 89-202*

Data Announcement 89-MGG-06

     In June and July 1980 and again in July and August 1981, the U.S. Geological Survey (USGS) conducted reconnaissance surveys from 171 degrees W to 173 degrees E longitude along the Aleutian Arc and Trench near the islands of Atka, Amlia, Kiska, Agattu and Seguam. A total of 2880 km of 24-channel seismic-reflection data were collected on the USGS Research Vessel S.P. Lee (USGS cruise identifiers L5-80-AA and L9-81-AA). These profiles for purchase from the National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)).

     Seismic energy was provided by a tuned array of five airguns with a total volume of 1212 cubic inches of air (L5-80-AA) or 1301 cubic inches of air (L9-81-AA) compressed to 1900 psi. The recording system during both cruises consisted of a 24-channel, 2400 meter streamer with a group interval of 100 m, and a GUS (Global Universal Science) model 4200 digital recording instrument. A shooting geometry of 50-m shotpoint intervals with 100-m group intervals resulted in a 24-fold data collection. Navigational control for the survey was provided by a Magnavox integrated navigation system using satellites fixes, doppler- sonar and during cruise L5-80-AA, Loran-C (Rho-Rho). A 2- millisecond sampling rate was used in the field; the data were later resampled to 4-milliseconds during the demultiplexing process. Record lengths of 8 to 16 seconds were used which, combined with a deep water delay, yielded up to 16 seconds of two way travel time. Processing was done at the USGS processing center in Menlo Park, California, in the sequence: editing- demultiplexing, velocity analysis, CDP stacking, deconvolution- filtering, and plotting on an electrostatic plotter. The seismic lines are available on plastic, paper sepia, paper blackline, and magnetic tape.

* "Multichannel Seismic-Reflection Profiles Collected in 1980 across the Aleutian Arc and Trench, Alaska" By D.M. Mann, D.W. Scholl and R.W. Sliter, U.S.G.S. Open File Report 89-202, U.S. Geological Survey, Menlo Park, California.

    "Multichannel Seismic Reflection Profiles Collected in 1981 across the Aleutian Arc and Trench, Alaska" By D.W. Scholl, D.M. Mann, T.L. Vallier and R.W. Sliter, U.S.G.S. Open File Report 88- 592, U.S. Geological Survey, Menlo Park, California.

DATA AVAILABLE (please refer to 9-digit product numbers when ordering).

multichannel seismic-reflection profiles (24 lines, 34 sections)
      (plastic sepia) Product #976F20174
      (paper sepia) Product #976F19174
      (blackline) Product #976F18174

3 trackline charts (scale: 1:500,000). Product #976F18174

1 magnetic tape containing shotpoint navigation, magnetics, bathymetry and gravity. Product #976H07174. This is also available on CD-ROM, Product #129F27001.

24 digital magnetic stack tapes (not deconvolved or band-pass filtered, Phoenix format). Product #967L07174.

24 digital magnetic demultiplexed tapes (edited for missed shots and muting times, Phoenix format - modified S.E.G.-X 32 bit floating point). Product #976L07175.