Yes and no. They are in close proximity to the tectonic boundaries / faults that have resulted in the 9.1 and 8.7 quakes. That level of activity alone indicates there is a degree of instability in the subplate. Being so large could also loosen up the conduits that bring the magma up into these volcanos. Or the broader tectonic activity is being reflected in increased volcanic activity since the volcanos are there because of the plate boundary.
Now before your brains ooze out of your ears from the above, I think there is a likelyhood that it is all related, however, the quakes didn't cause the increase in volcanic activity, but regional tectonic changes have caused both the earthquake and volcanic activities to increase. The key here is that we haven't observed tectonic activity on this level in historic times, so it is difficult to put an exact cause and effect together.
Thanks for your brilliant explanation. I understand.