ANISOTROPY IN KURIL-KAMCHATKA SUBDUCTION ZONE STRUCTURE

To constrain the orientation and extent of seismic velocity anisotropy in the Kuril-Kamchatka subduction zone, we have developed a technique that isolates anisotropy at shallow depths by differencing splitting observed in teleseismic shear-wave phases. Olivine a-axis orientations inferred from 29 sS-S phase pairs and two local S phases vary between the major tectonic components of the trench/back-arc system. Although the sS paths do not uniquely constrain a single model of anisotropy, a-axes are consistent with finite strain patterns predicted by plate convergence and back-arc spreading and shearing.