Seismic velocity azimuthal anisotropy of the Japan subduction zone: Constraints from P and S wave traveltimes

Xin Liu, Dapeng Zhao

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42 Citations (Scopus)


We present 3-D images of azimuthal anisotropy tomography of the crust and upper mantle of the Japan subduction zone, which are determined using a large number of high-quality P and S wave arrival time data of local earthquakes and teleseismic events. A tomographic method for P wave velocity azimuthal anisotropy is modified and extended to invert S wave traveltimes for 3-D S wave velocity azimuthal anisotropy. A joint inversion of the P and S wave data is conducted to constrain the 3-D azimuthal anisotropy of the Japan subduction zone. Our results show that the subducting Pacific and Philippine Sea (PHS) slabs exhibit mainly trench-parallel fast-velocity directions (FVDs), which may reflect frozen-in lattice-preferred orientation of aligned anisotropic minerals formed at the mid-ocean ridge as well as shape-preferred orientation such as normal faults produced at the outer-rise area near the trench axis. Trench-normal FVDs are generally revealed in the mantle wedge, which may reflect corner flows in the mantle wedge due to the plate subduction and dehydration. Trench-normal FVDs are also visible in the subslab mantle, which may reflect the subducting asthenosphere underlying the slabs. Our results also reveal toroidal mantle flows in and around a window (hole) in the PHS slab beneath SW Japan, suggesting that the occurrence of the PHS slab window may have caused a complex flow pattern in the mantle wedge above the Pacific slab.

Original languageEnglish
Pages (from-to)5086-5115
Number of pages30
JournalJournal of Geophysical Research: Solid Earth
Issue number7
Publication statusPublished - 2016 Jul 1


  • Japan subduction zone
  • Vp azimuthal anisotropy tomography
  • Vs azimuthal anisotropy tomography
  • joint inversion
  • mantle flow


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