I had missed this: EQF is correct about foreshocks to the west of the mainshock along the strike of the plate boundary that broke.

I was surprised that the focal mechanism is left-lateral: I would have expected right-lateral like is the case for southern boundary of Caribbean plate. Both plates have subduction zones to their east, and one would expect that the Scotia plate would be moving east relative to plate north and south. But Scotia Plate has a triple junction at the subduction zone so apparently the motion across the other plate boundary (spreading?) changes everything.

More info on plate motions would be interesting.

Chris