A FIRST LOOK AT THE UPPER MANTLE VELOCITY STRUCTURE OF THE ROSS SEA REGION, WEST ANTARCTICA, USING SURFACE WAVE INVERSION TECHNIQUES

Two-station surface wave inversion techniques provide a first look at the upper mantle structure beneath the Ross Sea region, West Antarctica. The Ross Sea region contains a series of extensional basins formed during the last tectonic activity in Antarctica, and is considered the boundary between the craton of East Antarctica and the younger West Antarctica.

Surface wave inversion of the entire southern hemisphere by Ritzwoller et al., (2001), reveal an anomalously slow velocity structure in all of West Antarctica and high velocity structure of the East Antarctic craton. Those findings are in agreement with other regional studies of Antarctica within East Antarctica, and along the boundary between East and West Antarctica.

This study addresses the Ross Sea, a region of thinned continental crust adjacent to the boundary between East and West Antarctica. Select seismic traces, recorded by broadband seismic stations circumscribing the Ross Sea Region, were inverted to determine velocity-depth profiles between stations across the region and along its boundaries.

Preliminary data are broadly consistent with previous findings in that the observed velocities are slower than those predicted by whole earth structure models. Transects within the Transantarctic Mountains show velocities that are slower than whole earth models at shallow lithospheric depths, which is consistent with thick crust. Meanwhile, transects crossing the Ross Sea show even slower velocities, suggesting warm upper mantle.