作者

Zhouchuan Huang, Dapeng Zhao, Liangshu Wang

发表日期

2011/4/1

期刊

Geophysical Research Letters

简介

We analyzed carefully shear‐wave splitting on 320 intermediate‐depth earthquakes occurring in the subducting Pacific slab in different frequency bands to investigate the S‐wave anisotropy and subduction dynamics under Northeast (NE) Japan. Our results show that the differential time between the fast and slow shear waves (δt) is definitely smaller (<0.2 s) in the high‐frequency band than that (0.3–0.4 s) in the low‐frequency band, and so the splitting parameters, especially δt, are strongly frequency‐dependent. Although the δt is indubitably smaller under NE Japan than the other subduction zones regardless of the frequency band, nine large δt values (0.5–0.7 s) are detected, which indicates that the anisotropy is potentially strong in NE Japan. Both the P and S wave anisotropy results in NE Japan are consistent with a model of subduction‐driven back‐arc spreading and convection in the mantle wedge causing trench‐normal fast orientations in the wedge and aligned faults and cracks in the subducting Pacific slab causing trench‐parallel fast orientations in the slab. When an S wave travels through the area with the multilayer orthogonal anisotropies, some of its splitting would be cancelled and thus small δt is observed.