Interseismic Strain Accumulation and Partitioning in Hispaniola from GNSS and InSAR

The northeastern Caribbean plate boundary provides a natural laboratory to investigate strain partitioning, fault slip rates, and crustal rheology in an actively deforming tectonic setting, where seismic hazard is a major concern. In this study, we combine GNSS and InSAR observations to improve our understanding of how strain is accommodated and how slip rates are distributed across this plate boundary, with a specific focus on the island of Hispaniola. The inclusion of InSAR data substantially mitigates the effects of the sparse and uneven spatial distribution of GNSS stations that limited earlier models. 

Using the combined GNSS-InSAR velocity field, we propose a new kinematic model that allows for internal deformation within selected tectonic blocks, incorporating InSAR-derived velocities for the first time in this type of modeling for the region. While our results are broadly consistent with previous studies, they identify and quantify compressional deformation within the Gulf of Gon\^ave, consistent with independent offshore observations.

We identify and quantify the impact of spatially correlated noise in the InSAR measurements, which is especially significant in this tropical, topographically complex region, where atmospheric artifacts can compete with or obscure the tectonic signal. We ultimately estimate surface strain rates and their associated uncertainties and compare these results with the geometry of faults imposed in block models as well as with the spatial distribution of current seismicity.

Our results confirm that the Enriquillo–Plantain Garden Fault Zone in southern Haiti is dominated by localized strike-slip motion. In contrast, deformation along the Septentrional Fault Zone in the Dominican Republic appears more distributed, suggesting that strain is accommodated by multiple fault strands rather than a single localized structure.