Mantle flow in the South Sandwich subduction environment from source‐side shear wave splitting

Abstract

The occurrence of seismic anisotropy in the Earth's upper mantle is a global phenomenon related to subcrustal deformation and flow processes. The shear wave splitting analysis method has led to a global set of anisotropy maps mainly derived from receiver‐side analysis. Remote places with few seismometers deployed remain unexamined. Source‐side splitting analysis allows mapping of mantle fabrics in these regions. Here, we investigate seismic anisotropy in the South Sandwich Islands subduction environment. Core‐reflected ScS waves recorded at the Neumayer seismograph network are corrected for well constrained receiver anisotropy and then analysed for source anisotropy. Sub‐slab mantle minerals are aligned horizontally almost parallel to the trench indicating a westward flow around the subducting slab. This is consistent with a model of horizontal mantle flow due to slab rollback that was previously inferred from marine and geochemical studies in the back‐arc region.