Tectonic and Seismologic Setting of the 22 September 2003, Puerto Plata, Dominican Republic Earthquake: Implications for Earthquake Hazard in Northern Hispaniola

Abstract

On 22 September 2003 a Mw 6.4 earthquake occurred beneath the northern coast of Hispaniola near the resort city of Puerto Plata, Dominican Republic. The earthquake caused extensive damage in Puerto Plata, as well as in the regional capitol of Santiago, located 30 km south of the coast (Figures 1 and 2). A large ( Mw 5.6) aftershock occurred about one hour after the mainshock, and felt aftershocks continued for more than a month. The large north-south extent of the aftershock zone, the mainshock focal mechanism, and geologic evidence for an active fold-thrust belt offshore of Hispaniola indicate that the 2003 earthquake occurred on the south-dipping thrust fault mapped offshore of and beneath Puerto Plata (Dolan et al. , 1998) (Figure 3). The Puerto Plata earthquake (as we refer to it) was thus the latest in a westward-propagating series of moderately large to great (M 6.4-8.1) earthquakes that have occurred along the Caribbean-North America plate boundary in Hispaniola since 1943 (Dolan and Wald, 1998). The occurrence of these earthquakes highlights the seismic risks affecting the rapidly developing and densely populated island of Hispaniola (which is shared by the Dominican Republic and Haiti). In particular, the occurrence of the 22 September 2003 earthquake focused attention on the nearby Septentrional Fault, a major left-lateral strike-slip fault that extends by various names for more than 1,000 km along the Caribbean-North America plate boundary (Mann et al. , 1984; Mann and Burke,1984; Calais et al. , 1992; Grindlay et al. , 1997; Dolan et al. , 1998; Mann et al. , 1998). Because of its proximity to major population centers in Hispaniola ( e.g. , Santiago, Dominican Republic and Cap Haitien, Haiti), the Septentrional Fault constitutes perhaps the most dangerous seismic source in the region. In this study, we …