Tectono-topographic response to stress changes induced by aseismic ridge subduction: Insights from analytical and 2-D finite element models

The subduction of aseismic oceanic ridges at convergent plate margins causes a reduction in submarine margin relief, which alters the balance of topographic and tectonic stresses. The stress changes increase the compression of the upper plate and may hence be relevant for understanding surface uplift and mountain building in response to ridge subduction. However, the detailed effects of relief changes and other parameters affecting the upper-plate force balance at subduction zones remain to be explored. Here we use analytical and two-dimensional finite-element models to investigate the effects of relief changes and additional parameters that may change during ridge subduction, including the initial trench depth, the slab dip angle, the slab curvature, and the submarine surface slope angle.

Our modeling results show that the compression caused by a decrease in submarine margin relief depends not only on the total relief change but also on the initial trench depth before ridge subduction and the geometry of the subducting slab. In addition, changes in the submarine surface slope angle during ridge subduction alter the compression of the upper-plate and may affect the total amount of surface uplift. Additional finite-element models with a setup of adjusted to the subduction of the Cocos Ridge (Central America) indicate that surface uplift in response to a reduction in submarine margin relief explains up to 50 % of the high topography in Costa Rica.