Might one consider what total force, and force per unit area i.e. pressure, could perhaps be considered to have shaken the recent (May 2015) volcano in Far East Islands? In order to consider momentum of mountain`s mass, one must affect inertia (in sense of law of inertia) of volcanic mass, most of which is sub-surface. What is the volcano`s mass? Could one assume that perhaps one has 90:10 mix of rock and metal; hence giving density? Then what might be considered a suitable volume for such volcano; thus deriving mass.
For a further assumption of maximum velocity i.e. related to frequency of vibration, of such object, might one estimate required acceleration, and hence overall force required to move such massive object. Then consider a plane (slice through entirety of such mountain) perpendicular to incoming direction of such impulse wave, relating to s and p recordings of an earthquake.
Thus by working backwards, could order of magnitude estimate of force required to move (vibrate) such mass, be considered equivalent to incoming overall force applied to such entire planar slice of mountain? Then could one estimate force per unit cross-sectional area i.e. pressure, stress of such incoming earthquake impulse wave? Could one assume instantaneous impulse, or integrate it over time (3 seconds?) interval; giving perhaps a summation of continuous applied pressure? Hence could one derive pressure, and thus force associated with such earthquake? Might this be just a lower limit as to force of earthquake impulse?
Might 2004 Sunda plate subduction fault earthquake off Sumatra be an example of setting a higher limit to such force, for a magnitude of ~ 8.8-9.3, greater than recent volcano in the Islands? The mass set in motion, of rock, sediment, and water, was probably much greater, since the break was ~1300 km, with part of it 90 km wide. Considering just non-compressible liquid set in motion, mass, and momentum change, and hence acceleration/force, must it have been much greater than for recent Island volcano, and much greater than any sub-surface or underwater nuclear explosion? Thus closer to any upper limit of force of such earthquake?