Reflection seismic, magnetic, gravimetric survey of the Pacific Margin of the Antarctic Peninsula (Summer 1989-90, 1991-1992)

During the Antarctic summers1989 - 1990 and 1991 - 1992, the
Osservatorio Geofisico Sperimentale realized a geophysical survey in
the Ross Sea, making use of the Research Vessel OGS - Explora,
collecting magnetic, gravimetric and seismic data. This research has
been carried out in the context of the Nation Research Program in
Antarctic (PNRA), coordinated by the Italian ENEA, under the auspices
of the Italian Ministry for Scientific and Technological Research.
The parameters for the different campaign are:

Summer 1989-90:

in cooperation with the United States Geological Survey (USGS) the
survey interested four different areas: the Scotia Plate, the
Antarctic Peninsula, the South Pacific Ocean and the Ross Sea. The
second part of the survey has been dedicated to the Pacific Margin of
the Antarctic Peninsula, where 7 profiles have been collected for a
total of about 1,550 km, by using the following parameters:

Coverage 3000%
Record Length 14 sec
Sample Rate 4 ms
Shot Interval 50 m
Streamer Length 3000 m
Streamer Depth 12 m
Number of Groups 120
Group Interval 25 m
Air-Guns:
- Total Volume 45.16 1
- Pressure 140 bar
- Depth 6 m

During February and March 1992:

The survey has been dedicated to three different areas where data have
been collected with different sampling parameters. The first area of
investigation interested the Hero Fracture Zone. In this area 16 lines
have been acquired with "standard sampling parameters" for a total of
2607 km. The second area investigated during the survey is the
Bransfield Strait. Due to moderate ice coverage and the particular
conformation of the area, it was necessary to use a shorter streamer
and a reduced airgun array. About 561 km of data along 6 lines have
been recorded in this area. In the third area, on the Southern Margin
of the Scotia Arc, 2 lines for a total amount of about 225 km have
been acquired. In this area a deep crustal configuration for the
streamer was used. This was the first test to use a very long streamer
in Antarctic waters. The characteristic of data acquisition system
were as follows:

AREA1 AREA2 AREA3
(HERO FRACTURE ZONE) (BRANSFIELD STRAIT) (SCOTIA ARC)
(62S, 69S, 61W, 79W) (62S, 64S, 57W, 63W) (60S, 62S, 50W, 52W)

Coverage 3000 % 3800 % 4500 %
Record Length 14 sec 7 sec 16 s
Sample Rate 4 ms 4 ms 4 ms
Shot Interval 50 m 25 m 50m
Streamer Length 3000 m 1900 m 4500 m
Streamer Depth 12 m 12 m 12 m
Number of Groups 120 76 180
Group Interval 25 m 25 m 25 m
Air-Guns
- Total Volume 45.16 1 37,4 1 72 1
- Pressure 140 bar 140 bar 140 bar
- Depth 6 m 6 m 6m

Source Name:Research Vessel > OGS-Explora

Sensor Name:ASTR1>Analogic streamer, Prakla
Sensor Name:MSREC1>Multichannel seismic recorder,Sercel 358
Sensor Name:BGV2>Gravimetric Bodenseewerk, KSS31
Sensor Name:GMG1>Magnetometer Geometrics, G801-803