Affiliation:
1. Institute for Geophysics & Department of Earth and Planetary Sciences Jackson School of Geosciences The University of Texas at Austin Austin TX USA
2. Department of Physics University of Colorado Boulder Boulder CO USA
3. Cooperative Institute for Research in Environmental Sciences and Department of Geological Sciences University of Colorado Boulder Boulder CO USA
Abstract
AbstractWe estimate depth‐dependent azimuthal anisotropy and shear wave velocity structure beneath the Alaska subduction zone by the inversion of a new Rayleigh wave dispersion dataset from 8 to 85 s period. We present a layered azimuthal anisotropy model from the forearc region offshore to the subduction zone onshore. In the forearc crust, we find a trench‐parallel pattern in the Semidi and Kodiak segments, while a trench‐oblique pattern is observed in the Shumagins segment. These fast directions agree well with the orientations of local faults. Within the subducted slab, a dichotomous pattern of anisotropy fast axes is observed along the trench, which is consistent with the orientation of fossil anisotropy generated at the mid‐ocean ridges of the Pacific‐Vancouver and Kula‐Pacific plates that is preserved during subduction. Beneath the subducted slab, a trench‐parallel pattern is observed near the trench, which may indicate the direction of mantle flow.
Funder
Division of Earth Sciences
Jackson School of Geosciences,University of Texas at Austin
Publisher
American Geophysical Union (AGU)