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National Centers for Environmental Information (NCEI)

Multichannel Seismic-Reflection Data
Bathymetry and Potential Field Data
Central and Northern New Hebrides Island Arc
Vanuatu to the Solomon Islands, Southwest Pacific
U.S.G.S. Open File Report 90-280*

Data Announcement 91-MGG-02

The U.S. Geological Survey conducted a geophysical survey in 1984 in the central and northern parts of the New Hebrides Arc with the R/V S.P. LEE (cruise identification L5-SP-84). These data for purchase from the National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)).

Approximately 2400 km of 24-fold multichannel seismic reflection data were collected along 37 lines. The seismic source consisted of a tuned, 5 airgun array totaling 1426 cubic inches, pressurized to 2000 psi, towed at a depth of approximately 10 meters. Individual gun volumes were usually 148, 194, 309, 309, and 466 cubic inches. The receiver consisted of a 24 channel hydrophone streamer with 100 meter group lengths containing 60 hydrophones in each group. The near channel offset from the airguns was 297 m and far channel offset 2611 m. The data were recorded with a Gus Model HDDR-4200 recording system. Shots were fired every 50 meters and records were sampled in the field at a 2 millisecond rate prior to processing. Primary navigation was by satellite.

The basic data processing sequence was editing-demultiplexing, static corrections, CDP sort, velocity analysis, and correction, stacking, and plotting on an electrostatic plotter. Particular attention was devoted to accurate velocity estimation through the use of a standard semblance plots and constant velocity stacks. The semblance velocity analyses were performed every 2.5 km (50 CDP's) along each line, using a summation of 3 to 5 adjacent CDP gathers for each analysis. The seismic lines are available on plastic, paper sepia, paper blackline, and magnetic tape. Digital geophysical data from this cruise are also available. To complement the seismic data, there are 2548 nautical miles of bathymetric data, 2067 nautical miles of magnetic data, and 2225 nautical miles of gravity data. The data are formatted in the standard MGD77 format and available as 1600 or 6250 bpi and in ASCII OR EBCDIC code tapes.

* Greene, H.G., Macfarlane, A., Smith, G.L., and Geist, E.L., Multichannel Seismic-Reflection Profiles from Vanuatu to the Solomon Islands collected in 1984, Open File Report 90-208, U.S. Geological Survey, Menlo Park, California.

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

42 multichannel seismic-reflection profiles for 37 lines
      (plastic sepia) Product #976F20178
      (paper sepia) Product #976F19178
      (blackline) Product #976F18178

3 trackline charts (scale: 1 3/8 inches = 10 nautical miles)
      Product #976A18178

1 magnetic tape containing shotpoint navigation, magnetics, bathymetry, and gravity. Product #976H07178. This is also available on CD-ROM, Product #129F27001.

37 digital stacked tapes in SEG-Y format. Product #976L07178