Present‐day shortening accommodated by folding, thrusting andstrike‐slip faulting in the Enriquillo basin of southern centralHispaniola: Implications for the regional seismic hazard

Abstract

AbstractHispaniola accommodates a significant portion of the present‐day convergence between Caribbean and North American plates. Located in southern Hispaniola, the Neogene Enriquillo basin is bounded by the Neiba and Bahoruco mountain ranges. The role of active individual faults and fault systems in this basin is not well understood, particularly their geometry and kinematics, slip rates and seismic activity. Knowing this information is important to characterize the active deformation pattern in southern Hispaniola, but it is also crucial to estimate the regional seismic hazard. Here, we analyze GPS geodetic data and seismicity and present the results of fault mapping of the Enriquillo basin based on tectonic field observations, radiocarbon and luminescence dating, remote sensing and regional magnetic data. These observations indicate that WNW to NW‐trending thrust faults and associate large‐scale folds, as well as minor strike‐slip and normal faults, have been active both in the Tertiary rocks within the mountain ranges and in the basin margins along the Quaternary. Inversion of fault‐slip data establishes that a NE‐directed shortening has controlled the formation of these structures. We propose a regional kinematic model in which the present‐day kinematics of each main fault depend strongly on its orientation with respect to the regional stress tensor. Computed seismic hazard defines a map pattern for the peak ground acceleration elongated to the main seismotectonic fault zones. Regions around the southwest Sierra de Neiba, the western Enriquillo basin and the northwest Sierra de Bahoruco, where peak ground acceleration exceed 500cm/s2, have a high seismic hazard.