Slab Morphology Around the Philippine Sea: New Insights From P‐Wave Mantle Tomography

We apply seismic tomography to 590,213 P‐wave arrival‐time data of 23,486 local earthquakes and 300,051 relative travel‐time residuals of 27,492 teleseismic events to study the 3‐D velocity structure of the crust and upper mantle beneath the entire Philippine Sea Plate (PSP) and its adjacent areas. Our results reveal significant high‐velocity anomalies beneath the Philippine Trench, the Japan‐Izu‐Bonin‐Mariana Trench, and the Nankai Trough, which reflect the subducted Philippine Sea slab, the Pacific slab, and the Shikoku Basin, respectively. On the basis of the tomographic images, we construct morphological models of these slabs. The slab morphologies become complex from the east to west. Taking into account previous results of geochemistry, paleomagnetism and numerical simulations, we deem that the complicated morphologies of the subducted slabs are related to the slab age, subduction rate, collision between different plates, clockwise rotation of the PSP, and retreat rate of trenches. The Philippine Sea Plate (PSP) is almost entirely surrounded by subduction zones. We use P‐wave tomography to study the 3‐D velocity structure of the crust and upper mantle beneath the entire PSP for a better understanding of the slab geometry and subduction dynamics. Our tomographic results reveal obvious high‐velocity (high‐V) anomalies beneath the trenches around the PSP, which reflect the subducting Philippine Sea slab, the Pacific slab, and the Shikoku Basin. We construct morphological models of these slabs according to their high‐V anomalies. These slab exhibit quite different morphologies. Taking into account previous geochemical, paleomagnetic and numerical simulation results, we think that the complex slab morphologies are related to the slab age, subduction rate, collision between different plates, clockwise rotation of the PSP, and retreat rate of oceanic trenches. P‐wave tomography is applied to investigate 3‐D velocity structure down to 800 km depth beneath the entire Philippine Sea PlateThe subducting Pacific and Philippine Sea slabs exhibit quite different morphologiesThe morphological differences are caused by the slab age, subduction history and interactions between slab and surrounding mantle P‐wave tomography is applied to investigate 3‐D velocity structure down to 800 km depth beneath the entire Philippine Sea Plate The subducting Pacific and Philippine Sea slabs exhibit quite different morphologies The morphological differences are caused by the slab age, subduction history and interactions between slab and surrounding mantle