Seismic wave propagation on a heterogeneous polar ice sheet

Abstract

Seismic wave propagation in a heterogeneous wave guide was studied using data obtained from several antarctic expeditions. The upper part of a polar ice sheet forms a wave guide in which a variety of body wave phases and surface waves can be propagated. The relative energy in successive compressional wave multiples can be predicted approximately from classical ray theory and measured velocity data. A compressional wave train observed on the Ross Ice Shelf appears to result from constructive interference of successive compressional wave multiples. Such wave trains are not recorded on the polar plateau, since the conditions for constructive interference do not exist. Analysis of surface wave dispersion from sites on the polar plateau and the Ross Ice Shelf suggests that the plateau wave guide is essentially isotropic but that the wave guide on the shelf is transversely isotropic and that compressional wave velocity anisotropy of up to 20% may be found. This suggests that the base of the wave guide is probably deeper than indicated by refraction data.