6.5 is no big deal.
A 6.5 under any US urban area is a disaster of immense proportions; Northridge (6.7) was deep, and much of its energy went in to fairly unpopulated areas; it also did 40 billion dollars worth of damage and would have killed hundreds if it wasn't in the wee hours of the morning.
A volcanic explosion deep underground which causess a vertical upheavel and a wave action radiating outward in all directions is the cause.
The above is abjectly false. What kook site did you get that from?
There is no horizontal movement in an earthquake.
There's plenty of vertical AND horizontal movements in earthquakes, measured by strong motion sensors.
The major damage is done to buildings on soft ground where the wave is unhindered rollong through the building lifting and droping sections in succession. On granit or hard rock formations the wave is dampened and damage is minor.
Well, the above is actually true, remarkably. You batted about 1-for-8 though.
As the energy released by the rapid dislocation of mass travels through the adjacent strata, how that adjacent strata reacts is key to damage of structures placed on its surface.
If the strata is loosely consolidated, and lubricated by ground water, the basin acts like a bowl full of jelly, refracting and reflecting energy over longer periods of time. Rigid structures sitting on the jelly are literally shaken to structural failure. Accelerations are not as great as at the point of orgin, but the reciprocating nature of the motion destroys.
If the adjacent strata is hard rock, the energy transmitted is unmodified, except by distance. The structure sitting on the hard strata endures only a few sharp jolts without great motion displacements. A structure might be lifted sharply off it's foundation but the displacement is quick and short, limiting damage to cracks and small ruptures.