Very interesting. Especially if your conclusion that the quake occurred some 500+ feet below the mountain's summit is correct. Even an M2.0 there would be of real concern, and would, of course, be suggestive of magma movement.

Couple of caveats, though. Depth measurements as reported on USGS and other such sites are always rather suspect, and I don't think they reference local surface elevation. I'm a little unclear on it, but I think they reference sea level, or the geoid, or something. The quake likely occurred at much greater depth below the summit.

I just looked at the topo - the quake was centered 14 miles east of Mt. Shasta . . .

Mike Williams

Mike Williams