I have been watching this earthquake cluster for a few weeks and it’s interesting. Normally you get a bunch of quakes like this they are after shocks from a larger quake but looking at thedata for this area and there is no big quake associated with this cluster. Yes there was an 8 in 2006, but the activity from it stiopped long ago.
But there could be a pattern. Looking at the data from 2005 and 2006 there was an increase in activity, building from smaller quakes with 5’s and 6’s until there was the large 8 and then the activity ramped down again.
Will that happen again, has it happened more than once before, and the answer to the latter question is yes, look at 1995 and 1996. But the pattern also indicates that this is a very active zone and before every big 7 or higher quake it gets more active, lets go a big one, lets the resulting stress off and then after a month or so of aftershocks goes quiet for a few years. It is just restarting this activity again and I expect the largish 7 or so in October to December period.
The islands are on the same set of faults the Japan quake was on and is suffering the same issues of subduction of the pacific plate.