Seismic hazard of the Enriquillo–Plantain Garden fault in Haiti inferred from palaeoseismology

Abstract

The Enriquillo–Plantain Garden fault zone is the primary plate-bounding fault system in Haiti and was initially thought to be responsible for the 2010 earthquake. Palaeoseismic analyses of the fault system indicate that it ruptured during a large earthquake in either 1750 or 1770, but did not rupture during the 2010 earthquake. The Enriquillo–Plantain Garden fault zone is recognized as one of the primary plate-bounding fault systems in Haiti1,2. The strike-slip fault runs adjacent to the city of Port-au-Prince and was initially thought to be the source of the 12 January 2010, Mw 7.0 earthquake. Haiti experienced significant earthquakes in 1751 and 1770 (refs 3, 4, 5), but the role of the Enriquillo–Plantain Garden fault zone in these earthquakes is poorly known. We use satellite imagery, aerial photography, light detection and ranging (LIDAR) and field investigations to document Quaternary activity on the Enriquillo–Plantain Garden fault. We report late Quaternary, left-lateral offsets of up to 160 m, and a set of small offsets ranging from 1.3 to 3.3 m that we associate with one of the eighteenth century earthquakes. The size of the small offsets implies that the historical earthquake was larger than Mw 7.0, but probably smaller than Mw 7.6. We found no significant surface rupture associated with the 2010 earthquake. The lack of surface rupture, coupled with other seismologic, geologic and geodetic observations6,7, suggests that little, if any, accumulated strain was released on the Enriquillo–Plantain Garden fault in the 2010 earthquake. These results confirm that the Enriquillo–Plantain Garden fault remains a significant seismic hazard.