On Thu, 28 Feb 2008 02:26:30 -0000, "Clive George"
wrote:

"MM" wrote in message
.. .

Yes, I can believe that. But having experienced that tremor as the
first in my life, I just marvel at the way mother nature can gather
enough energy to wobble an entire country a few inches this way and
that. It is to me as fascinating as trying to explain television to
Charles Dickens would have been. There is nothing comparable that is
man-made. Explosives would merely result in devastation.

Well, interestingly enough, not necessarily.

If you're trying to shift rock, eg for road building or quarrying, you use
explosive. Put it near the surface and you get a bang and lots of little
bits of rock flying anywhere - but not much volume shifted.
Put it deep, and it looks a lot less spectacular - but shatters rather more
rock, provided you put enough in.

So if you go deep enough, you'll end up with a shock wave, ie earthquake.
See underground nuclear tests - how do you think they're detected? Locally
stuff is pulverised, but futher away it's more like what you want.

But yes, it is an interesting reminder of the scales involved in plate
tectonics - which is significantly larger than what we experienced last
night.

I suppose it isn't actually power as such that shifts the surface of
the earth we happen to be on at the time when an earthquake or tremor
happens, but simply the effect of gravity on very large masses of rock
miles down.

MM