National Centers for Environmental Information (NCEI)

Multichannel Seismic-Reflection Profiles
Western Ross Sea - Antarctica
USGS Open File Report 86-634*

Data Announcement 87-MGG-09

Approximately 2,350-line km of multichannel seismic- reflection data, as well as 4,500 km of other geophysical profile data including gravity, magnetic gradiometer, and echo-sounding profiles for the western Ross Sea, Antarctica are available for purchase from the National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)). The data were collected on the U.S. Geological Survey (USGS) R/V S.P. LEE, Cruise No. L284AN available to NGDC (now NCEI) for public dissemination.

The seismic source consisted of a tuned five-airgun array totaling 1,311 cu.in. pressurized to 1,900 psi, towed at a depth of 10.5 m. The receiver consisted of a 24-channel hydrophone streamer, with 100-m group lengths containing 60 hydrophones in each group. The streamer was towed at a depth of 12.5 m. The data were recorded with a GUS Model HDDR-4200 recording system. All lines were recorded to 12 sec, with exception of Line 407 (15 sec) and Line 419 (8 sec). Magnetic data were recorded continuously with a Geometrics proton-procession gradiometer to remove the large temporal magnetic variations commonly recorded at polar latitudes. The gradiometer system consisted of two proton- precession magnetometers separated horizontally by 500 ft (152 m) with the forward sensor lying 225 m aft of the ship. Both sensors were towed at a depth of approximately 20-40m. Data were sampled at 4-sec intervals. Gravity data were recorded continuously with a LaCoste and Romberg sea gravimeter (S53) on a two-axis stabilized platform. The data were collected at 20-sec intervals and subsequently desampled to 2 min or greater for plotting and modeling. All digital navigation, bathymetry, gravity, and magnetic gradiometer data have been condensed into a single file conforming to the marine geophysical data exchange format "MGD77".
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* Marine Geophysical Data from the western Ross Sea, Antarctica," by A.K. Cooper, D.M. Mann, J.R. Childs (USGS, Menlo Park, CA), and F.J. Davey (Geophysics Div., Dept of Industrial & Scientific Research, Wellington, NZ), OFR 86- 634, USGS, Menlo Park, CA.

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

1.  Multichannel-Seismic Data

    24-fold multichannel seismic data for 19 lines/19
    sections.

          (plastic sepia)  Product #976F20160
          (paper sepia)    Product #976F19160
          (blackline)      Product #976F18160

    19 sections of navigation, bathymetric, free-air
    gravity, and magnetic gradiometer profiles plotted at a
    horizontal scale identical to the multichannel seismic
    reflection data.

          (plastic sepia)  Product #976J20160
          (paper sepia)    Product #976J19160
          (blackline)      Product #976J18160

    1 navigation chart  Product #976A18160

2.  Digital Geophysics Data

    Digital navigation, shot-point navigation, bathymetry,
    gravity and magnetics on magnetic tape,
    Product #976A07160.  This is also available on CD-ROM,
    Product #129F27001.

3.  Magnetic Tapes

    19 Digital magnetic stacked tapes.  Product #976L07160
    19 Digital magnetic sort tapes.  Product #976L07161