Structure of the upper mantle under the Antarctic Plate from surface wave tomography

We have analyzed surface wave data for 245 events occurring in Antarctica and surrounding oceans during,years 1991-1999. We first apply dispersion analysis to the fundamental mode of Rayleigh waves for periods ranging from 20 to 150 sec. We then invert path-averaged dispersion curves to obtain 2D maps of group velocity for different periods, represented by splines on a grid with 250 km spacing, with considerably more detail tail than that achieved by global models. We finally use group velocity maps in a nonlinear inversion for the regional 3D v(SV) structure of the upper mantle. The resulting model shows thick continental roots under East Antarctica, reaching depths below 200 km; low velocities under oceanic, ridges, mostly confined to the upper 150 kill; and a slow area under the Ross Sea volcanic centres, extending all the way down to 200 km, beyond which our data loose resolving power.