M 5.8 - 4 km E of Moca, Puerto Rico | 2010-05-16 05:16:10 (UTC)18.400°N 67.070°W113.0 km depth - USGS Poster

Tectonic Summary - The Puerto Rico earthquake of May 16, 2010, occurred in an inclined seismic zone that dips south from the Puerto Rico Trench and that consists of subducted lithosphere of the North America plate. The broad-scale tectonics of the Puerto Rico region are determined by the motion of the Caribbean plate east-northeast at a velocity of about 20 mm/yr with respect to the North America plate. The North America plate is thrust beneath the Caribbean plate at the Puerto Rico Trench, and is seismically active to depths of about 150 km.

M 7.0 - 10 km SE of Léogâne, Haiti | 2010-01-12 21:53:10 (UTC)18.443°N 72.571°W13.0 km depth - USGS Poster

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.