The stress state implied by dislocation models of subduction deformation

Abstract

Dislocation models of the earthquake cycle are often employed to predict surface deformations above a subduction zone. However, these models, being based entirely on a kinematic formulation of subduction behaviour, place no constraints on the subsurface stress field. Here, the stress state predicted by an elastic dislocation model is shown to exhibit characteristics inconsistent with those anticipated based on physical models of subduction behaviour. In particular, the model predicts an unreasonable distribution of stress along the interface between the overriding and subducting plates. The net shear traction integrates to zero along the interface, so significant shear must act on the overriding plate in the updip direction, opposite to that of the relative direction of motion of the subducting slab. Quantitative calculations using an elastic half‐space representation of the Earth are employed to illustrate the inconsistencies inherent in the dislocation model. Analytic expressions for this case are extended to allow for calculation of the stress components over the entire half‐space. © 1995 American Geophysical Union. All Rights Reserved