P and S wave tomography and anisotropy in Northwest Pacific and East Asia: Constraints on stagnant slab and intraplate volcanism

作者：Wei Wei, Dapeng Zhao, Jiandong Xu, Feixiang Wei, Guoming Liu · 发表于：Journal of Geophysical Research Solid Earth · 年份：2015 · DOI：10.1002/2014jb011254 · 被引用次数：148 · 研究领域：High-pressure geophysics and materials、earthquake and tectonic studies、Geological and Geochemical Analysis

Abstract We determined three‐dimensional P and S wave velocities and P wave azimuthal anisotropic tomography of the Northwest Pacific subduction zones by inverting 1,225,086 P wave and 335,117 S wave arrival times from 13,413 earthquakes. Our results show some differences between P and S wave images for the stagnant Pacific slab in the mantle transition zone (MTZ) beneath Northeast China. The stagnant slab looks thicker in the P wave image than that in the S wave image, which may reflects the effects of both hydration and lower temperature in the MTZ, though differences in the resolution of P and S wave tomography may also have some effects. The Changbai intraplate volcanism is caused by hot and wet upwelling in the big mantle wedge above the stagnant Pacific slab. Our P wave anisotropy tomography shows that the fast velocity direction (FVD) in the subducting Philippine Sea plate beneath the Ryukyu arc is NE‐SW (trench parallel), which is consistent with the spreading direction of the West Philippine Basin during its initial opening stage, suggesting that it may reflect the fossil anisotropy. A striking variation of the FVD with depth is revealed in the subducting Pacific slab beneath the Northeast Japan arc, which may be caused by slab dehydration that changed elastic properties of the slab with depth. The FVD in the mantle wedge beneath the Northeast Japan and Ryukyu arcs is trench normal, which reflects subduction‐induced convection. Beneath the Kuril and Izu‐Bonin arcs wh...