About the sound waves being loud enough to register seismically, I believe that is possible, but I have no references for you. I was just thinking of reports of windows rattling from sound alone - my mother has described this from low flying fighter jets from an airforce base, or even at concert events - the sound can reach a level that 'shakes' cars, rib cages, buildings. I could be displaying my ignorance, but it seems to me that the sound associated with this meteor was truly impressive, and that is evidenced by those sound waves actually shaking the ground enough to be picked up by seismometers. FWIW.