The Seychelles Plateau is believed to be continental material isolated during the separation of Africa from India some 60 million years ago. A 10 month deployment of broad-band and short-period 3-component seismometers started February 2003 with the aim of studying the heterogeneity and anisotropy of the upper-mantle beneath the Seychelles. Questions to be addressed are the role of the Seychelles during breakup, evidence of subsequent plume activity and the extent to which the plateau is continental in nature. This experiment links with a collaborative controlled-source experiment to study the crust and upper-mantle of the Seychelles-Laxmi Ridge conjugate margin pair (Imperial College, Southampton and Leeds University) . The aim of this experiment is to help establish the role of extension rate in the development of rifted margins.
A variety of techniques will be used to investigate upper-mantle heterogeneity and anisotropy. For example, shear-wave splitting analysis will be used to investigate whether the anisotropy is associated with absolute plate motions or deformation associated with break-up. Tomographic inversion of travel-times will be used to produce images of the velocity structure of the mantle beneath the plateau. Receiver functions will be used to investigate crustal thicknesses and deeper mantle discontinuities.
Methods & Equipment