Seismic anisotropy is used to investigate deformation in subduction zones, where many dynamic processes are at play. Recently, a global pattern of trench-parallel subslab mantle deformation in subduction zones has emerged through shear-wave splitting measurements. We investigated the Lesser Antilles in the Caribbean to find that the northeast corner of the subduction zone presents an interesting setting in which to observe seismic anisotropy, where the trench-parallel subslab splitting signal may become complicated due to oblique subduction. Here, we present 201 shear-wave splitting measurements of SKS and SKKS phases from teleseismic events recorded at 20 broadband seismic stations in the northeastern Caribbean. We observe average apparent fast polarization directions (ϕ) that are primarily trench-parallel, with average delay times (δt) ranging from 0.5 s to 2.0 s. Our results suggest trench-parallel mantle flow is continuous along the northeastern plate boundary where the Lesser Antilles subduction zone changes strike from nearly east-west trending to north-south trending. Our preferred explanation for the observed splitting pattern is that the dominant process is subslab mantle return flow.
- Received 12 January 2015.
- Revision received 17 April 2015.
- Accepted 16 May 2015.
- © 2015 Geological Society of America