I was recently and for the first time caught in an earthquake. This being my first time, I freaked out and had no idea whether the building was going to collapse or not. I was later told that this earthquake was nothing to worry about because it was due to the volcanic activity of a nearby volcano (4.9 on the Richter, 1km depth). It caused minor damages near to the volcano, but nothing measurable in our location about 30 km away.
This got me thinking - if volcanic activity is less dangerous than plate activity (because it's closer to the surface, perhaps?), is there some upper limit to the scale of such earthquakes? I suppose that earthquakes and volcanic activity are correlated in some way, but I'm not considering the volcanic activity due to plate movement, rather the "normal" activity of active volcanos.
What is the largest magnitude measured of an earthquake attributable solely to volcanic activity?