From longitudinal slab curvature to slab rheology

Abstract

The curvature of a subducting lithosphere is chiefly controlled by the viscosity ratio between the slab and the surrounding mantle. On the basis of a semi-analytical flow model, we explore the rheological dependence of the geometrical response of a viscous slab subjected to toroidal mantle flow. Mantle flow is excited by slab retreat at a prescribed mean velocity and is iteratively solved for by using a stream function approach, in turn providing the stresses that bend the slab. Comparison between model predictions and geophysical observations of slab curvature gives an average slab-to-mantle viscosity ratio of 45.