National Centers for Environmental Information (NCEI)
MULTICHANNEL SEISMIC-REFLECTION DATA
BATHYMETRY AND POTENTIAL FIELD DATA
USGS OPEN FILE REPORT 90-100
Data Announcement 91-MGG-01
In 1982, a geophysical survey in the territorial waters of
Vanuatu was conducted by the U.S. Geological Survey's R/V S.P.
Lee (cruise identifier L6-SP-82). 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 40 lines. The seismic source consisted
of a tuned, 5 airgun array totaling 1311 cubic inches,
pressurized to 2000 psi, towed at a depth of approximately 10.5
meters. Individual gun volumes were usually 148, 194, 194, 309,
and 466 cubic inches. The receiver consisted of a 24 channel
hydrophone 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 but resampled to a 4 millisecond
rate prior to processing. Primary navigation was by satellite.
The basic data processing sequence was editing-demultiplexing,
static corrections, CDP sort, velocity analysis, NMO correction,
stacking, and plotting on an electrostatic plotter. Particular
attention was devoted to accurate velocity estimation through the
use of 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 3-5 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 from
our office. To complement the seismic data, there are 2375
nautical miles of bathymetry data, 2216 nautical miles of
magnetic data, and 2302 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 Collected
in 1982, Open File Report 90-100, U.S. Geological Survey, Menlo
DATA AVAILABLE (please refer to 9-digit product numbers when
41 multichannel seismic-reflection profiles for 40 lines
(plastic sepia) Product #976F20179
(paper sepia) Product #976F19179
(blackline) Product #976F18179
2 trackline charts (scale: 1.5 inches = 10 nautical miles)
1 magnetic tape containing shotpoint navigation, magnetics,
bathymetry, and gravity. Product #976H07179. This is also
available on CD-ROM, Product #129F27001.
40 digital stacked tapes in SEG-Y format. Product #976L07179