Frequency-dependent shear-wave splitting and multilayer anisotropy in northeast Japan

Zhouchuan Huang, Dapeng Zhao, Liangshu Wang

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36 Citations (Scopus)


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.

Original languageEnglish
Article numberL08302
JournalGeophysical Research Letters
Issue number8
Publication statusPublished - 2011 Apr 28


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