M 7.0 - 10 km SE of Léogâne, Haiti

Tectonic Summary

The January 12, 2010, M 7.0 Haiti earthquake occurred as the result of shallow strike-slip faulting in the boundary region separating the Caribbean plate and the North America plate. Focal mechanism solutions indicate that rupture occurred on either a right-lateral southeast-striking fault or on a left-lateral west-southwest-striking fault. Of these two possible fault orientations, finite-fault modeling of globally recorded seismic data is more consistent with slip on the west-southwest-striking (left-lateral) fault. At the location of the earthquake, the local plate boundary is dominated by left-lateral strike-slip motion and compression, and accommodates about 20 mm of slip per year, with the Caribbean plate moving eastward relative to the North America plate.

Haiti occupies the western part of the island of Hispaniola, one of the Greater Antilles Islands, situated between Puerto Rico and Cuba. At the location of the January 12th earthquake, motion between the Caribbean and North America plates is partitioned between two major east-west-trending, strike-slip fault systems—the Septentrional fault system in northern Haiti and the Enriquillo-Plantain Garden fault system in southern Haiti.

The location and focal mechanism solutions of the earthquake are consistent with the event resulting from a combination of reverse and left-lateral strike-slip faulting on the Enriquillo-Plantain Garden fault system. The overall Enriquillo-Plantain Garden fault system accommodates about 7 mm/yr of motion, nearly half the total oblique convergence between the Caribbean and North America plates. The January 12th mainshock did not produce observable surface displacement on the geomorphologically well-expressed main strand of the Enriquillo-Plantain Garden fault system, but appears instead to have primarily involved rupture of a fault or faults distinct from the previously mapped principal strand, causing substantial uplift of the Léogâne delta.

The Enriquillo-Plantain Garden fault zone (EPGFZ) had not produced a major earthquake in recent decades. The EPGFZ is the likely source of historical large earthquakes in 1860, 1770, and 1751, though none of these has been confirmed in the field as associated with this fault. The sequence of events possibly associated with the Enriquillo fault in 1751–1860 are as follows:

October 18, 1751: a major earthquake caused heavy destruction in the Gulf of Azua (the eastern end of the Enriquillo fault); this earthquake also generated a tsunami. It is unclear if the rupture occurred on the Muertos thrust belt or on the eastern end of the Enriquillo fault.

November 21, 1751: a major earthquake destroyed Port-au-Prince but was centered to the east of the city on the Plaine du Cul-de-Sac.

June 3, 1770: a major earthquake destroyed Port-au-Prince again and appeared to be centered west of the city. As a result of the 1751 and 1770 earthquakes and minor earthquakes that occurred between them, local authorities required building with wood and forbade building with masonry.

April 8, 1860: a major earthquake occurred farther west of the 2010 earthquake and was accompanied by a tsunami.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)