Slab Pull Drives IBM Trench Advance Despite the Weakened Philippine Sea Plate

Abstract

AbstractThe mechanism behind the significant Izu‐Bonin‐Mariana (IBM) trench advance is still controversial. We conduct slab subduction numerical models that reproduce the spatio‐temporal tectonic evolution of the Philippine Sea region to investigate whether slab pull from the Ryukyu subduction zone can cross the weakened Philippine Sea Plate and act on the IBM trench. Model results show that the lithospheric strengthening and weakening effects cancel out each other during the rift stage so that the slab pull from the Ryukyu Trench can transmit through the weak fossil spreading centers and intra‐arc rifts and drive the Izu‐Bonin Trench's advance. In contrast, lithospheric weakening overwhelms lithospheric strengthening and impedes stress transfer in the back‐arc spreading stage, suggesting that the slab pull cannot directly pull the Mariana Trench to advance at present. Our study indicates that extreme rheological parameters are not needed for the IBM trench advance, despite the Philippine Sea Plate is weakened.