here is an update to this series of interesting earthquakes. http://earthjay.com/earthquakes/20130523_sea_okhotsk/sea_okhostk_20130524_1000.PNG
this one is along strike and at a similar depth to the M8.3. also an extensional earthquake, but with a more intermediate dip. it will be interesting to see what the microseismicity (or slow slip earthquakes, or non volcanic tremor, each filling in different parts of the “bandwidth” of known seismic phenomena) is doing updip of this M6.8.
will these all be foreshocks to a large subduction zone earthquake? or, as suggested above, is this part of the subduction zone “slipping” in different ways, possibly aseismically? there have been large to great subduction zone earthquakes in this region before, but that does not necessarily rule out some different fault behavior. alternately, these all could be a result of the earthquake in 2006 (tho a while ago, and stress changes due to nearby earthquakes are small, the 2006 eq is in the region to the south of this current swarm). see the usgs page below for a map of historic earthquakes, including 2006.
we would generally expect large to great earthquakes again in this location, but we learn new things every day. subduction zone geology is a rapidly evolving field.
here is the usgs link (check out the moment tensor by clicking “technical information”)
update 10:22 AM: the 1952 earthquake was also in this region. actually, now that i look at it, these M4-5’s are in a region of the 1952 EQ that did not slip!