Seismic Anisotropy Evidence for Ductile Deformation of the Forearc Lithospheric Mantle in Subduction Zones

Jian Wang, Xiaoge Huang, Dapeng Zhao, Zhenxing Yao

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

Seismic anisotropy provides important information on the structure and geodynamics of the Earth. The forearc mantle wedge in subduction zones mainly exhibits trench-parallel azimuthal anisotropy globally, which is inconsistent with the model of olivine a axis aligning with the slab-driven corner flow. Its formation mechanism is currently unclear. Here we present high-resolution 3-D P wave anisotropic tomography of the Tohoku subduction zone. We suggest that ductile deformation of the forearc lithospheric mantle of the overriding plate induces the trench-parallel azimuthal anisotropy and positive radial anisotropy (i.e., horizontal velocity > vertical velocity) in Tohoku. Our results provide the first seismic anisotropic evidence for the slab-mantle decoupling at a common depth of ~70 km. On the basis of the high-resolution seismic images, we propose a geodynamic model suggesting that the forearc mantle wedge anisotropy is produced via ductile deformation of dry olivine or hydrous antigorite lithospheric mantle, which accords well with the trench-parallel shear wave splitting measurements dominant in subduction zones globally.

Original languageEnglish
Pages (from-to)7013-7027
Number of pages15
JournalJournal of Geophysical Research: Solid Earth
Volume124
Issue number7
DOIs
Publication statusPublished - 2019 Jan 1

Keywords

  • lithospheric deformation
  • seismic anisotropy
  • subduction zone
  • tomography

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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