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Frequency‐dependent shear‐wave splitting and multilayer anisotropy in northeast Japan
Author(s) -
Huang Zhouchuan,
Zhao Dapeng,
Wang Liangshu
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl046804
Subject(s) - subduction , geology , shear wave splitting , slab , anisotropy , seismology , trench , s wave , shear (geology) , mantle wedge , wedge (geometry) , geophysics , mantle (geology) , petrology , tectonics , physics , optics , materials science , layer (electronics) , composite material
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 ( δ t) 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 δ t, are strongly frequency‐dependent. Although the δ t is indubitably smaller under NE Japan than the other subduction zones regardless of the frequency band, nine large δ t 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 δ t is observed.