9:15 AM - 9:35 AM
[SIT29-02] Seismic imaging of the subducting Philippine Sea plate
Keywords:Philippine Sea plate, Pacific plate, Aseismic slab, Earthquakes, Seismic tomography
Our P-wave anisotropy tomography shows that the fast-velocity direction (FVD) in the subducting PHS slab 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. Significant FVD variations with depth are revealed in the subducting Pacific slab beneath the NE 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 NE Japan and Ryukyu arcs is trench normal, which reflects subduction-induced convection. Beneath the Kuril and Izu-Bonin arcs where oblique subduction occurs, the FVD in the mantle wedge is nearly normal to the moving direction of the down-going Pacific plate, suggesting that the oblique subduction together with the complex slab morphology have disturbed the mantle flow.