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 (similar to 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.

Automated summary

The convergence of tectonic plates at subduction zones causes flexural bending of the subducting plate, leading to normal faulting and influencing water budget and seismic behavior. 3-D plate bending deformations can affect slab pull force, particularly when deflection changes along the trench.