Improving subduction interface implementation in dynamic numerical models

This study focuses on methodological issues related to dynamic subduction zone modelling. Numerical models often employ an entrained weak layer (WL approach) to facilitate decoupling between the subducting and overriding plates. In such a setup, the kinematics of the flow lead to width variations in the subduction interface. When a uniform-width interface is prescribed, a transient evolution of the interface thickness occurs, during which the volmetric flux along the interface profile establishes equilibrium. Width variations can exceed 4× during this stage, which may impact the effective strength of the interface, both through physical effects if the rheology is linear, and numerical effects if the fault becomes poorly resolved. This transient process induces strong sensitivity to model resolution, and may present a significant challenge to reproducibility. Developing more robust ways to model the subduction interface will enable fully dynamic models to address sensitive subduction-zone processes, such as metamorphism near the slab top. In this study we discuss a simple strategy aimed at improving the standard WL approach. By prescribing a variable thickness weak layer at the outset of the model, and by controlling the limits of the layer thickness during the model evolution, we find improved stability and resolution convergence of the models.

Replacement of Ensemble Averaging by the Use of a Broadband Source in Scattering of Light from a One-Dimensional Randomly Rough Interface between Two Dielectric Media

By the use of phase perturbation theory we show that if a single realization of a one-dimensional randomly rough interface between two dielectric media is illuminated at normal incidence from either medium by a broadband Gaussian beam, it produces a scattered field whose differential reflection coefficient closely matches the result produced by averaging the differential reflection coefficient produced by a monochromatic incident beam over the ensemble of realizations of the interface profile function.