Thanks Isis, that fella has done some really comprehensive work eh. Good on him.

His conclusions are that the booms, when plotted, story by story correspond to EQ activity.

That may well be the case. But, like this thread, he hasnt gone in the 'why' of it. LOts of info but no reason.

Is it plates grinding? In other EQs are there booms from this?

Is it pockets of gas exploding? anagin is this a common thing?

If they are man made, is it deliberate explosions to make areas more fluid and less rigid, to lessen EQ impact? absorb the shock waves?

Is it from deep drilling, glassing the fault line together by detonating mini nukes?

Is it collapsing cave systems? man made or natural.

Gas would seem to be the obvious one, and maybe why the fracking craze has been so prevalent of late - to reduce the amount of flammable materials?

If that is the case, then foreknowledge is in play.