Donald, from your post it kind of sounds like you are not familiar with subduction zones (I may be wrong). I won't explain subduction or plate tectonics here-its easy to find and learn, if you can pry yourself away from the Creationist presentations. Plate tectonics and creationism do nolt go together well-at least you can't explain plate tectonics if you believe in a very young earth (in which case I'm wasting my time). The first quakes of this swarm were located SW of the trench-the historical seismicity shows that the slab dips NE from the trench. These first quakes were normal faulting=stretching of subducting plate-then oblique normal. The M7.3 and a following large quake were located near but NE of the trench-and were thrust events, with the likely nodal plane being the one that dips gently NE. It is likely that these are subduction quakes. The M7.1 yesterday does not have a focal mechanism yet (weekend). All of the few that I looked at are shallow. Most tectonocists (is that a word?) think that subduction is driven by gravity-the subducted plate is denser than the upper mantle that it is being subducted into (because the basalt is converted by pressure into denser eclogite). The slab drags the plate behind it. That is why there is stretching of the subducting plate. So, it seems more likely that a deep subduction quake will trigger shallow quakes than the other way around, and a deep magnitude M8+ is unlikely. Or, another way to look at this-oceanic lithosphere is subducting beneath oceanic lithospere here (I don't know if one side is thickened), and the big interplate quakes would only be shallow because the plates are not in contact deep-the deep quakes would be inside of the slab. Someone could look hard at the history of quakes at this location on this subduction zone-that is something Lowell Whiteside is best qualified to do, but he does not post here any more.
Chris