National Geophysical Data Center

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). The data were collected on the U.S. Geological Survey (USGS) R/V S.P. LEE, Cruise No. L284AN available to NGDC 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

Please contact NGDC for prices.