Interseismic Strain Accumulation and Partitioning in Hispaniola From GNSS and InSAR

Abstract

We combine GNSS and InSAR observations to constrain the spatial distribution of strain across the northeastern Caribbean plate boundary, focusing on Hispaniola, to investigate strain partitioning and fault slip rates in an actively deforming tectonic setting with significant seismic hazard. Including InSAR data substantially mitigates the effects of the sparse and uneven spatial distribution of GNSS stations that limited earlier models. We propose a new kinematic model that allows for internal deformation within selected tectonic blocks. While our results are broadly consistent with previous studies, we quantify the amount of compressional deformation within the Gulf of Gonâve, consistent with independent offshore observations, which likely materialize the eastern boundary of the Gonâve microplate. We assess the impact of spatially correlated noise in the InSAR measurements, which is especially significant in this tropical, topographically complex region, where atmospheric artifacts can obscure tectonic signals. We estimate surface strain rates and their associated uncertainties and compare these results with the geometry of faults imposed in block models. Our results confirm localized strain on the Enriquillo–Plantain Garden Fault at rates consistent with previous studies, with along–strike variations in fault geometry. In contrast, deformation in the northern Dominican Republic does not localize on the mapped trace of the Septentrional Fault but involves a broader area, in particular to the south of the main fault trace. The Septentrional Fault Zone and its subsidiary fault splays should all be considered capable of producing large earthquakes.