The Antarctic upper mantle: 
Recent advances and future challenges using surface waves

Nikolai M. Shapiro and Michael H. Ritzwoller
Department of Physics
University of Colorado at Boulder
Boulder, CO 80309-0390
nshapiro@ciei.colorado.edu


The use of surface wave data to constrain mantle structure at high 
southern latitudes helps to circumvent problems created by the 
relative paucity of receiving stations on the Antarctic continent 
and the shortage of intraplate seismicity across the Antarctic plate. 
For this reason, there is a long history of surface wave studies 
of Antarctica. Only recently, however, have sufficient 
broad-band seismic data accumulated to the point that surface wave
tomography can yield relatively high resolution images across much 
of the Antarctic region.

The long wave paths 
needed to image the upper mantle beneath Antarctica make it 
advisable to apply diffraction tomography which 
accounts for the finite extent of surface-wave Fresnel zones, models
wavefront healing, and provides more realistic resolution estimates
than traditional ray-theory based tomographic methods.
We discuss a recent model of the upper mantle at high 
southern latitudes produced from a large data set of fundamental 
mode surface wave dispersion measurements that has been constructed
using diffraction tomography followed by Monte-Carlo inversion.
We discuss several aspects of the resulting model focusing on the
transition in lithospheric structure between East and West Antarctica.
We also discuss preliminary efforts to estimate mantle temperatures
in Antarctica which are relevant for inferring geothermal flux and
mantle viscosity.

Finally, we discuss how new broad-band stations in Antarctic-Array
may improve lateral resolution. A particular need for Antarctic 
surface-wave tomography is improving the number of measurements at periods
greater than about 100 sec, particularly for Love-waves which
are important to estimate radial anisotropy. This will require the use 
genuinely broad-band instruments in future Antarctic seismic
deployments and attention to be paid to noise on the horizontal
components.