Numerical models of subduction and forearc deformation

Abstract

Summary. Finite element models for shallow subduction produce realistic behaviour for a wide variety of mechanical strength and density distributions. Characteristic displacements are found to occur even without a discrete low‐strength megathrust if there is a high‐density subducted plate to localize lithospheric compression. A high‐density plate is itself unnecessary in the presence of a low‐strength megathrust and regional compression. Successful finite element models produce an outer arc at the top of the trench slope, and forearc basin with geometry characteristic of natural analogues. These structural features occur by upward inelastic bending of the lithospheric wedge overlying the megathrust. This mechanically unstable behaviour may dissipate significant energy and cause the megathrust to migrate continuously by accretion, tectonic erosion, or abandonment and reinitiation farther offshore. Upward bending in the overriding plate is promoted by low megathrust dip, low megathrust shear strength, and high horizontal compression in the overriding plate. Copyright © 1985, Wiley Blackwell. All rights reserved