Study of plate deformation and stress in subduction processes using two-dimensional numerical models

Abstract

Two-dimensional finite element modeling is used to model subduction of an oceanic lithospheric plate beneath continental lithosphere. The subduction process is initiated along a preexisting inclined fault and continues until reaching 400 km of total convergence. The lithosphere is assumed to be underlain by an inviscid asthenosphere. Different rheological laws have been considered for the lithosphere, including elasticity and elastoplasticity. The modeling shows that both the stress system in the plates and the surface topography are strongly dependent on two main parameters: the density contrast between lithosphere and asthenosphere (Δρ = ρL - ρA) and the coefficient of friction along the subduction plane. Varying these two parameters allows explanation of the main characteristics of real subduction zones and results in two major regimes manifested by extension or compression in the arc-back arc system. Extension and back arc rifting corresponds to a positive density contrast and a low coefficient of friction, while negative Δρ values and/or high friction leads to a compressional regime. The coexistence of trench arc compression and back arc tension is only possible for a coefficient of friction lower than 0.1. The results of the numerical experiments agree with those of experimental modeling conducted under similar physical assumptions. Copyright 1997 by the American Geophysical Union.