Detached Pacific Slab Beneath the Philippine Sea Plate and Its Geodynamical Implications

Abstract

AbstractFormation and evolution of the Philippine Sea Plate (PSP) are still highly debated, mainly because the PSP has been surrounded by subduction zones since its inception. Therefore, it is vital to determine a new tomographic model with higher resolution to precisely portray the subducted slabs beneath and around the PSP, in particular, the subducted Pacific slab that has played an essential role in the PSP formation and evolution. In this study, an updated tomographic model is obtained by inverting a large number of P‐wave arrival times of local and regional earthquakes in and around the PSP. Our tomography reveals a detached piece of the Pacific slab in the mantle transition zone beneath the middle PSP, which may be mainly related to the PSP clockwise rotation and transform or strike‐slip faults in this region. The detached Pacific slab may promote the formation and evolution of the Shikoku and Parece‐Vela basins and the Mariana Trough by inducing hot mantle upwelling. Our tomography also reveals isolated high‐velocity anomalies beneath the southernmost PSP, which may reflect remnants of the subducted slab at the beginning of the PSP formation. A high‐velocity gap appears beneath the southern PSP, which may reflect the influence of a mantle plume.