Since 1964 the lower magnitude threshold has gradually decreased to less than 4.0 and there are regions where dense local networks allow location of earthquakes down to very low magnitudes. Volcanic earthquake swarms are excluded. The deepest earthquakes in this region occur at depths of a little greater than 200 kilometers. The overall pattern is fairly typical of an island arc. The shallowest earthquakes occur on the Atlantic Ocean side of the arc.
Depths increase across the arc to the Caribbean.
Within this pattern there are clusters of higher levels of activity, regions where the level is lower than the average and regions where the depths appear to be anomalous.