Saw this interesting blog on the latest swarm NW of PR
http://www.earthquakesummary.info/MODERATE EARTHQUAKES SHAKE ANCHORAGE, ALASKA AND DOMINICAN REPUBLIC
EARTHQUAKE SUMMARY FOR JULY 28, 2011
A moderate earthquake of M 4.6 was preceded by a foreshock of M 4.0 in the Dominican Republic area today.
Two earthquakes of larger magnitude have hit the region in the past year - an M 5.4 on March 16, 2011 and an M 5.5 four months earlier on November 13, 2010.
The four month interval between these events was continued with today's earthquake.
We believe this epicenter is near the likely rupture point of the coming great earthquake on the Puerto Rico Trench.
This event could occur this year, most likely in connection with a strong retroactive moving hurricane and a strong geomagnetic storm.
Such an event would likely trigger a major tsunami which could cause considerable destruction in the northern Caribbean and possibly along the U.S. Gulf Coast region.
Today's activity occurs following the passage of Tropical Storm Don through the region two days ago.
At the time we suggested the possibility of such a series of earthquakes associated with this tropical storm as follows.