Hi Brian, I was coming here to post the same thing. They are not giving the focal mechanisms. From the little plate boundary maps, it looks like some of these are on a spreading center within stepovers of the Great Sumatra fault. The depths look like they are defaults for location program where given as 10 km. The subduction zone that broke in 2004 is below this area, but may be deep enough there to not be locked.

The tectonic setting of these quakes is like Gulf of California (except there is not an active subduction zone in GOF.

Chris