Yield failure of the subducting plate at the Mariana Trench

Two tectonic plates converge at subduction zones where the subducting plate bends. Flexural bending of a subducting plate at a trench results in pervasive normal faulting, providing conduits for plate hydration and influencing the water budget and seismic behavior of the plate interface. 2-D plate bending simulations have demonstrated high strains due to strong bending may result in loss of strength of the lithosphere and intraplate earthquakes near the trench axis. However 3-D plate bending deformation may affect the along-strike slab pull force, especially when the deflection changes along the trench. Here we simulated the 3-D plate bending deformation and calculated bending stresses, and brittle failure of the Pacific plate at the Mariana Trench. We find that both the plate deflection and the yield zone depth (~16–20 km) increases from the northern to southern Mariana Trench. The water flux in the plate at the southern Mariana Trench is estimated to be about 15% greater than that of the northern Mariana Trench. By comparing with 2-D models, we further find that the 2-D approaches may undereastimate the yield zone depth as they ignored the along-trench effects of plate deflection. The new results provide a self-consistent framework for interpretation of the observed surface normal faults, extensional earthquakes, and the inferred hydration of the subducting plate as constrained by seismic velocity anomalies.