Chris at Highly Allochthonous has put together a good post and collection of maps of the Caribbean tectonic scenario.
Here is another good map from the USGS with the locations and dates of big earthquakes over the last few hundred years.
Source: Uri ten Brink, USGS
Its not just the recent quake but a lot of the past big earthquakes also fall a way south of the northern plate boundary along subsidiary faults.
Via: Discovery News