There was a M4.7 quake north of Puerto Rico followed by a swarm of aftershocks, many over M3. The USGS site does not give a focal mechnism. But, zooming into the map:
http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/PR2/18.20.-67.-65.php

These aftershocks are distributed along a N-S line across 60 or 70 km, far bigger than a M4.7 would have broken (I'd guess that a M4.7 would break about 1 km, maybe less). Some of the other swarms in the last year here have been along N-S lines. I'd still like to know what is going on here.
Chris