Seismic Structure and Geodynamics of the Philippine Sea Plate and its Surrounding Subduction Zones

The Philippine Sea Plate (PSP) is one of the most important elements of plate tectonics in the western Pacific region. The most conspicuous feature of the PSP is that it is surrounded by subduction zones. Here, we review main geophysical studies in the past two decades on the evolution and general structure of the PSP and its surrounding subduction zones, as well as related seismic and volcanic activities. These studies revealed strong structural heterogeneities in all parts of the PSP and its surrounding subduction zones. Fluids from dehydration reactions of the subducting Pacific and Philippine Sea slabs cause active arc volcanism and affect the generation of large crustal earthquakes, megathrust earthquakes, and intraslab events. Tears and windows are revealed in the subducting Philippine Sea slab, which may be facilitated by subduction of oceanic ridges. There are interactions between the subducting Pacific and Philippine Sea slabs. Significant seismic anisotropy occurs in the mantle above and below the subducting slabs, which reflects mantle flows induced by the plate subductions. These studies shed new light on seismotectonics, volcanism, and geodynamics in the western Pacific and Southeast Asian regions, which are important for both scientific research and reduction of seismic, volcanic, and tsunami hazards.