Radial and Azimuthal Anisotropy Tomography of the NE Japan Subduction Zone: Implications for the Pacific Slab and Mantle Wedge Dynamics

Abstract

Abstract We investigate slab and mantle structure of the NE Japan subduction zone from P wave azimuthal and radial anisotropy using travel time tomography. Trench normal E‐W‐trending azimuthal anisotropy (AA) and radial anisotropy (RA) with VP V > VP H are found in the mantle wedge, which supports the existence of small‐scale convection in the mantle wedge with flow‐induced LPO of mantle minerals. In the subducting Pacific slab, trench parallel N‐S‐trending AA and RA with VP H > VP V are obtained. Considering the effect of dip of the subducting slab on apparent anisotropy, we suggest that both characteristics can be explained by the presence of laminar structure, in addition to AA frozen‐in in the subducting plate prior to subduction.