Modeling Seismic Anisotropy Beneath the Island of Hispaniola via the Harmonic Decomposition of Receiver Functions

Abstract

AbstractThe Caribbean Island of Hispaniola resulted from plate convergence that brought together distinct terranes and may include one or more active microplates. These processes may have brought seismically anisotropic materials to the island or created anisotropic structures through deformation. Our goal is to identify and model interfaces that bound seismically anisotropic media and/or dipping interfaces between isotropic layers beneath Hispaniola and assess the implications of our results for the region's tectonics. We perform harmonic decomposition of receiver function gathers for 17 broadband seismic stations deployed on the island. Our results reveal (a) a layer bounded by interfaces that produce opposite polarity on the transverse receiver functions at 25 and 41 km depth in the northern and eastern Dominican Republic that corresponds to the subducting North American oceanic lithosphere, (b) a layer at ∼8–17 km depth (also bounded by interfaces that produce opposite polarity) beneath the Cordillera Central in the central and eastern parts of the island that may indicate the crystalline, well‐differentiated lower crust of this long‐lived terrane, and (c) an interface that bounds anisotropic material at 22 km depth beneath southwestern Hispaniola. This last interface may correspond to the underthrusting Caribbean Large Igneous Province (CLIP), in which case it would mark the CLIP's upper boundary and the lower boundary is too gradual a transition to produce conversions.