National Centers for Environmental Information (NCEI)

Multichannel Seismic-Reflection Profiles

EASTERN GULF OF ALASKA
USGS OPEN FILE REPORT 87-148*

Data Announcement 87-MGG-18

Approximately 2,108 km of 24-channel seismic-reflection profiles in the Eastern Gulf of Alaska for purchase from the National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)). These profiles were collected during the summer of 1978 aboard the R/V S.P. Lee, Cruise L3-78-EG, by the U.S. Geological Survey (USGS), Department of Interior.

The seismic energy was provided by a tuned array of five airguns with a total volume of 1,326 cu. in. of air compressed to approximately 1,900 psi. The recording system consisted of a 24- channel, 2,400-m long 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 resulted in the 24-fold data collection. Navigational control for the survey was provided by a Marconi integrated navigation system using transit satellites and Doppler sonar augmented by Loran C (Rho-Rho). The data were recorded at a 2-msec sampling rate and were later desampled to 4 msec during the demultiplexing process. Data were recorded for 6-sec subbottom time, which, combined with a deep-water delay, yielded a total of approximately 11 sec of two-way travel time. The processing sequence included demultiplexing, velocity analysis, CDP stacking, deconvolution-filtering, and plotting on an electrostatic plotter. The illustration below shows the trackline chart for shotpoint navigation. The seismic lines are available on plastic, paper sepia, paper blackline, and magnetic tape.

* "Multichannel Seismic-Reflection Profiles Collected in 1978 in the Eastern Gulf of Alaska," by Terry R. Bruns, Dennis M. Mann, and Ray W. Sliter, USGS Open File Report No. 87-148, U.S. Geological Survey, Menlo Park.

DATA AVAILABLE

1.  Common-Depth Point Seismic Sections:  24-fold multichannel
seismic data for 28 lines, 30 sections.

          (plastic sepia)  Product #976F20155
          (paper sepia)    Product #976F19155
          (blackline)      Product #976F18155

2.  Navigation Sections:  available at no charge.  Please call
for details.

3.  Digital Geophysics Data:
          Navigation, bathymetric, gravity, magnetic, gradiometer
          data, and shot-point numbers:

1 magnetic tape (9-track, 1600 bpi, ASCII).  Product #976H07155.
This is also available on CD-ROM, Product #129F27001.


4.  CDP Stack Tapes:

          28 Digital magnetic stack tapes
               (Not deconvolved or band-pass filtered.  Copies of
                tapes and description of tape format available).
                Product #976L07155

          28 Digital magnetic demultiplexed stack tapes
               (Edited for missed shots, blanking and muting
                times.
                Product #976L07156