Evaluation of Geomorphic Proxies from High Resolution Topographic Dems in Oblique Subduction Zones: Western Puerto Rico

Abstract

We examined geomorphic proxies in oblique subduction zones with very low tectonic uplift rate using western Puerto Rico as case study. The Puerto Rico and the Virgin Island microplate is located at the NE corner of the Caribbean plate oblique subduction boundary with the North America plate. Seismic hazard is a major concern in the region, due to the frequent medium to low activity in the island. Active faulting has been suggested specially in the western part of the island, but limited research has been done about location and mechanisms of the faults. Geomorphic proxies have been recognized to be useful to estimate parameters like spatial and temporal distribution of rock uplift, and to assess the maturity and stability of drainage basins. Nevertheless, geomorphic proxies have been mainly tested in collisional margins with high uplift rates and rift settings with moderate uplift rates. This work aims to test three independent geomorphic proxies, Chi integral (X), Asymmetric Factor (AF) and Normalized Steepness (Ksn) in western Puerto Rico to compare them with passive seismic data and lineament analysis using digital elevation model (DEM) from LiDAR, SRTM and NED data. Our goals with this work are (1) Test the usefulness of geomorphic proxies in subduction zones with low uplift rates (2) Identify surface lineaments in southwestern Puerto Rico that could be indicative of faulting (3) Correlate this information with the distribution pattern of the geomorphic proxies, to identify faults that could be active or reactivated. Performing geomorphic proxies analysis in Puerto Rico provided significant results in subduction zones with very low tectonic uplift. In addition our results provide some insight of the displacement of faults in south Boquerón Bay, La Parguera, Punta Montalva, Guánica and Cerro Goden fault. It also suggest possible reactivation of faults in South Boquerón Bay, Sierra Bermeja, La Parguera, Guánica, San Germán Fault, La Torre fault and Cerro Goden Fault.