Active Tectonics in Southern Haiti and Surface Rupture of the 14 August 2021 Earthquake

Abstract

The 14 August 2021 earthquake occurred along the southern peninsula of Haiti only 11 years after the 12 January 2010 devastating earthquake. According to seismological and geodetic data, the events are both complex involving more than one fault. The 2021 rupture mainly portrayed reverse motion to the east near L’Asile town and left-lateral strike-slip motion to the west near Camp-Perrin town and Macaya mountain. A few days after the 2021 event, we conducted the first post-seismic field reconnaissance along the left-lateral Enriquillo-Plantain Garden Fault (EPGF) zone from L’Asile to Macaya mountain. We found numerous fresh cracks and landslides along that fault zone. The 111 cracks are mainly E-W-striking, some are oriented WNW-ESE, consistent with fault orientation in the area. In addition, the biggest cracks are mostly located to the west of the rupture zone, some of them may be potential fault surface rupture as revealed by seismological data. Furthermore, our observations along the northern coast of the southern peninsula revealed no significant coseismic coastal uplift as also suggested by InSAR data. Besides that field reconnaissance, we revisited the fault map around the epicentral area using high-resolution LiDAR data, Pléiades imagery and aerial photographs. We identified several left-lateral offsets of tens of meters corresponding to successive slips along the EPGF from L’Asile to Macaya mountain. In addition to the strike-slip deformation, we identified numerous geomorphic features related to long-term tectonic uplift to the north of the EPGF surface trace near the eastern part of the 2021 rupture. Those features are strikingly rare to the south. Such a pattern may indicate that the EPGF is north-dipping in the area. The 14 August 2021 rupture offers a new opportunity to constrain the kinematics and geometry of the EPGF system in southern Haiti.