Seismic Azimuthal Anisotropy Beneath the Alaska Subduction Zone

Abstract We 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 sub...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: Chuanming Liu, Anne F. Sheehan, Michael H. Ritzwoller
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2024
Subjects:
seismic anisotropy
surface wave tomography
Alaska subduction zone
azimuthal anisotropy
surface wave
aleutian subduction zone
Geophysics. Cosmic physics
QC801-809
Pacific
Kodiak
Alaska
Online Access:https://doi.org/10.1029/2024GL109758
https://doaj.org/article/e5d82138422e4a4aaf9dd87b130a849f
Description
Summary:Abstract We 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.

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