There were M4.8 and 4.7 quakes in California at the northern end of the main aftershock zone for the Baja quake. There was just a M7.4 with a focal mechanism consistent with subduction near offshore northern Sumatra, which is part of the rupture zone of either the M9.1 or 9.2 Dec 2004 quake or the M8.7 March 2005 quake (I forget which,probably the latter?). I guess stress and strain have had some time to build in Sumatra so at some point these are not aftershocks.
Chris