Probing sub-slab anisotropy beneath Central America and Tonga from geodynamic models

Abstract:

A number of conceptual models have been proposed to explain trench parallel shear wave splitting observations beneath subducting slabs. Recently, Lynner and Long (2014) tested several of these conceptual models against a quasi-global source-side shear wave splitting dataset and found that a model in which sub-slab dynamics varies with the age of the down-going plate best matches the observations. A major limitation of that study, however, was the employment of very simplified geodynamics; especially in cases that invoke 3-dimensional return flow, where highly complex flow patterns are expected near and around slab edges. Here, we examine sub-slab shear wave splitting patterns from geodynamic models aimed at mimicking real world subduction beneath Central American and Tonga; which exhibit entrained and 3D return flow patterns, respectively. Using a variety of olivine LPO and other anisotropic fabrics, we compare shear wave splitting from these models against actual source-side measurements in order to better understand sub-slab deformation.