Character of the Caribbean–Gônave–North America plate boundaries in the upper mantle based on shear‐wave splitting

Abstract

We present new shear‐wave splitting measurements of SKS, SKKS, PKS, and sSKS phases from eight stations in the northern Caribbean. Prior to this work, shear‐wave splitting analysis of the northern Caribbean boundary was only evaluated at a station in Puerto Rico. Stations that lie within several tens of kilometers of microplate boundaries have mean fast polarization directions parallel to the boundary and have delay times greater than 1 s. Stations more than several tens of kilometers away from microplate boundaries show no evidence for an anisotropic upper mantle. Stations in Cuba and Jamaica have fast axes oriented ∼100° with delay times of ∼1.5 s, indicating that the east‐striking left‐lateral strike‐slip faults that define the north and south boundaries of the Gônave microplate continue into the upper mantle. A station located in Antigua, where the North America plate subducts beneath the Caribbean plate, has a high degree of splitting with the fast axis parallel to the trench. Based on our results, the deformation related to the presence of microplates in the northern Caribbean extends into the upper mantle.