Poster of the Haiti Earthquake of 12 January 2010 - Magnitude 7.0

Tectonic Summary

The January 12, 2010, Haiti earthquake occurred in the boundary region separating the Caribbean plate and the North America plate. This plate boundary is dominated by left-lateral strike slip motion and compression, and accommodates about 20 mm/y slip, with the Caribbean plate moving eastward with respect 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 longitude of the January 12 earthquake, motion between the Caribbean and North American 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 of the earthquake are consistent with the event having occurred as 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/y of motion, nearly half the total oblique convergence between the Caribbean and North America plates. The January 12 main shock 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 significant uplift of the Léogâne delta.

The Enriquillo-Plantain Garden fault system has 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.

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) which also generated a tsunami. It is unclear if the rupture occurred on the Muertos thrust belt or on the eastern end of Enriquillo Fault.

Nov. 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 ones in between, the authorities required building with wood and forbade building with masonry.

April 8, 1860: there was a major earthquake farther west accompanied by a tsunami.

See also:

Poster of the Seismicity of the Caribbean Plate and Vicinity

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