The ARAD 3-D (Anatomy of a Ridge Axis Discontinuity)
EW9707 cruise was undertaken in September and October 1997 to provide both
refelction and wide-angle seismic data for the study of the overlapping
spreading centre (OSC) at 9 degrees 3 minutes N on the
East Pacific Rise. The project is a joint endeavour between the University
of Cambridge / BIRPS and the Scripps Institute of Oceanography (SIO). The
significance of the experiment lies in the fact that it was the first truly
3-D survey of an OSC.
In Cambridge we are attempting to determine the large scale 3-D velocity
structure of the OSC by using recordings of the densely spaced
airgun shots by OBS's. The seismic images obtained will be free from unwanted
artefacts that would otherwise be included in traditional 2-D profiles.
This bathymetric map shows the overlapping spreading centre at
9degrees 3minutes N. YThe locations of the Ocean Bottom Seismometers (OBS's)
are indicated with the grid marking where 201 parallel MCS lines with a
spacing of 100m were shot during the EW9707 cruise. The numbered
instruments were designed and built at Cambridge.
Two limbs of the ridge segments show decline of magmatic supply towardsd
the ridge axis discontinuity. (MacDonald et al 1984)
Region of extensive partial melt under the overlap basin (Lonsdale 1983)
This page last updated on May 6th 1998