Why does Haiti experience earthquakes?

Answer 1

On a global tectonic scale, Haiti is located near the northern boundary of the Caribbean plate, close to where it meets the North American plate.

On a subregional tectonic scale, Haiti is situated on the eastern end of of a smaller plate that separates the Caribbean and the North American plates known as the Gonave micro-plate. This micro-plate and hence Haiti is bounded to the north by the Oriente and Septentrional Fracture Zones and to the south by the Enriquillo-Plantain Garden fault which are both transform faults (very similar to the San Andreas Fault in the USA).

The north American plate and the Caribbean plate are both moving East at approximately 3 to 5 cm per year, however they are moving at slightly different velocities which causes stress to accumulate in the earth's crust over time, causing energy to be stored in the form of elastic strain (like that in a compressed spring). Ultimately this stress may exceed the shear strength of the crust in the fault zone causing a sudden brittle failure or rupture. This in turn causes movement and a sudden release of the stored elastic strain energy in the form of seismic waves (as well as heat and sound).

Please see the related question for more information.