Antarctic Ice Properties Revealed From Teleseismic P Wave Coda Autocorrelation

Antarctica is largely covered by an ice cap of a variable thickness characterized by relatively low density and seismic velocities. Passive seismological deployments have a limited use in imaging a thin ice layer because of the dominance of a relatively low-frequency content in the teleseismic wavefield. Here we use passive seismological data and an improved autocorrelation method utilizing P wave coda to image the ice cover. The resulting autocorrelograms are interpreted as reflectivity records from a virtual source on the surface and reflection pulses at the ice base. We convert the reflection delay of P waves to the ice thickness measurements using a homogeneous P wave speed compatible with previous studies. Apart from P wave reflectivity, we obtain S wave reflectivity from the autocorrelation of radial component. The ratio of S wave and P wave reflection times represents a measurement of the P over S wave speed ratio (and Poisson's ratio). The successful application to unveil the Antarctic ice sheet properties presented here opens a way for future studies to measure properties of the ice cover in Antarctica, other continents, and icy planets in future space missions.