TY - JOUR
T1 - Depth-varying azimuthal anisotropy in the Tohoku subduction channel
AU - Liu, Xin
AU - Zhao, Dapeng
N1 - Funding Information:
We thank the Hi-net data center and the JMA Unified Earthquake Catalog for providing the high-quality arrival-time data used in this study (www.hinet.bosai.go.jp). We appreciate the helpful suggestions from Profs. Martha Savage and Jeffrey Park, and discussions with Drs. Zhouchuan Huang, You Tian and Shujuan Zhao. We are very grateful to Prof. An Yin (the Editor) and two anonymous reviewers who provided thoughtful review comments and suggestions which have improved this paper. The free software GMT (Wessel and Smith, 1998) is used for making most of the figures. This work was supported by grants from the JSPS (Kiban-S 23224012) and the MEXT (26106005) to D. Zhao, and a grant from the Chinese NSFC (41602207) to X. Liu.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/9/1
Y1 - 2017/9/1
N2 - We determine a detailed 3-D model of azimuthal anisotropy tomography of the Tohoku subduction zone from the Japan Trench outer-rise to the back-arc near the Japan Sea coast, using a large number of high-quality P and S wave arrival-time data of local earthquakes recorded by the dense seismic network on the Japan Islands. Depth-varying seismic azimuthal anisotropy is revealed in the Tohoku subduction channel. The shallow portion of the Tohoku megathrust zone (<30 km depth) generally exhibits trench-normal fast-velocity directions (FVDs) except for the source area of the 2011 Tohoku-oki earthquake (Mw 9.0) where the FVD is nearly trench-parallel, whereas the deeper portion of the megathrust zone (at depths of ∼30–50 km) mainly exhibits trench-parallel FVDs. Trench-normal FVDs are revealed in the mantle wedge beneath the volcanic front and the back-arc. The Pacific plate mainly exhibits trench-parallel FVDs, except for the top portion of the subducting Pacific slab where visible trench-normal FVDs are revealed. A qualitative tectonic model is proposed to interpret such anisotropic features, suggesting transposition of earlier fabrics in the oceanic lithosphere into subduction-induced new structures in the subduction channel.
AB - We determine a detailed 3-D model of azimuthal anisotropy tomography of the Tohoku subduction zone from the Japan Trench outer-rise to the back-arc near the Japan Sea coast, using a large number of high-quality P and S wave arrival-time data of local earthquakes recorded by the dense seismic network on the Japan Islands. Depth-varying seismic azimuthal anisotropy is revealed in the Tohoku subduction channel. The shallow portion of the Tohoku megathrust zone (<30 km depth) generally exhibits trench-normal fast-velocity directions (FVDs) except for the source area of the 2011 Tohoku-oki earthquake (Mw 9.0) where the FVD is nearly trench-parallel, whereas the deeper portion of the megathrust zone (at depths of ∼30–50 km) mainly exhibits trench-parallel FVDs. Trench-normal FVDs are revealed in the mantle wedge beneath the volcanic front and the back-arc. The Pacific plate mainly exhibits trench-parallel FVDs, except for the top portion of the subducting Pacific slab where visible trench-normal FVDs are revealed. A qualitative tectonic model is proposed to interpret such anisotropic features, suggesting transposition of earlier fabrics in the oceanic lithosphere into subduction-induced new structures in the subduction channel.
KW - azimuthal anisotropy
KW - megathrust earthquakes
KW - subduction
KW - Tohoku
KW - tomography
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U2 - 10.1016/j.epsl.2017.05.034
DO - 10.1016/j.epsl.2017.05.034
M3 - Article
AN - SCOPUS:85020438995
SN - 0012-821X
VL - 473
SP - 33
EP - 43
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -