but I wasn't aware of this part:
Satellite measurements show that the Caribbean plate is moving east over the Atlantic plate at around 2 centimetres per year. Measurements over several decades show that the sum of all earthquakes that strike on "splinter faults" on the Caribbean plate, like Tuesday's, have accounted for around half of the energy associated with this movement, leaving the other half stored up in the system. Some of the remainder may be accommodated by slow creep along the region's faults, but McGuire and his colleagues are concerned that much of the stress may be accumulating on the undersea thrust fault to the east.
If that stress were to be released on the submarine fault, it could trigger a catastrophic tsunami of the scale of the 26 December 2004 Indian Ocean disaster.
McGuire released a report warning of this danger in 2008 (PDF). Along with the entire Caribbean, Central America, the Gulf coast of the US and the north coast of South America would be at risk from such a tsunami.
In particular, geological measurements indicate that stress is building in the section of submarine fault between easternmost Dominican Republic and the island of Guadeloupe. Large earthquakes of magnitude 8.5 to 9.0 could rupture the entire 1000-kilometre length of the fault, McGuire and his colleagues wrote in their report.
A thrust quake that breaks loose a 600-mile fault line? Yeeks. That would be Bad.
I've read a bit on quakes, but for some reason never read- or noticed, one- this subduction zone. A tsunami rolling up from the Caribbean into the Gulf... Make that Very Bad. And that's not counting the damage from the quake itself.
Pointed to by Insty.