Your (our) chances of catching Saddam setting off a device (even a low-yield one) are better than the 1 in 4 you assume below. You're taking me back to my geology days and I don't purport to remember everything but here is a snip.
Earthquakes produce two kinds of shockwaves: S waves and P waves. They each travel through different parts of the earth (I can't remember which) and at different speeds, which is how we determine the "epicentre" of the quake. Three or more stations triangulate the location of the epicentre by determining the difference in arrival times of the P and S waves. Since the speed of each is finite and known, the distance from one station to the epicentre can be determined (both waves are created at the same time) and we can then triangulate.
Underground nuclear tests, on the other hand, only produce one of the two waves (I can't remember which, but it's the same wave each time, i.e. either P or S but it never alternates from one to the other). That is the definitive test that a device has been set off.
Seismographs are horrendously sensitive (i.e. they can detect footsteps if you want them to) so I think it's quite unlikely that a device of any significant size (and here I'm thinking over one ton yield) would go unnoticed. If the device was placed in a cavity and assuming the detonation didn't cause the cavity to collapse, I suppose there is a likelihood that the test could go unnoticed but I think any type of rock that would sustain the blast without collapsing would likely transmit the blast waves through the surrounding soil.
Any Civil Engineers or Geologists on the list might want to corroborate what I've said, or even refute.
From: Edward Oleen [mailto:email@example.com]
Sent: February 25, 2003 1:13 AM
Subject: [cdn-nucl-l] Re: detection limits for underground weapons tests
Thanks a lot, folks.
What I gather from all the replys (half a dozen by
now) is that IF Saddam and his Merry Men tested a
small device (of a few tons) in a large cavity we
might detect it. If he had the patience to wait
for a large earthquake in the region - like
another quake in Turkey or Iran, for instance -
(come to think of it, that pretty much brackets
the region, doesn't it...) - THEN his
few-ton-yield device - a
"proof-of-principle-and-engineering" device -
could, quite possibly, go unnoticed - being
regarded as just another after-shock. This is
especially likely if he takes care not to allow
any escape of fission products. I think enough
about the Plowshare series has been made public
that he shouldn't have any trouble in figuring out
what to do.
And IF his test was run just after something
MAJOR, like the anticipated rupture under or near
Ankara, with a subsequent large loss of life
(which would sort of take our mind(s) off of
looking for a underground test), and IF he managed
to avoid radiation release, and IF he didn't get a
"run-away", which would jack his test up into the
easily-detectable range.... THEN the first thing
we might know about his new toy is when he
utilizes his now-proven device to get rid of some
I've got three IF's in the previous sentence. I
don't think any of them are too unlikely to be
achieved. Assume 90% probability of his getting
away with any one of them: that means 72%
probability of getting away with all three. I
really don't want to hang my hat on one chance in
four of catching him.
Of course, if my third IF fails, and he shoots for
50 tons but achieves 500 or 5000... and we thus
catch him at it... well, so what? he now knows
that his design WORKS, and all he has to do is
build more, if he hasn't already, and fit one onto
a SCUD, and declare it and leave us to guess the
target... Remember just how successful our Desert
Storm "scud-hunts" were? I sure do. We took out
some milk trucks thinking they were
scud-transporters and/or fuelers, as I recall.
His Western Desert region is real empty, and we
have never properly searched it on the ground,
remember? I'm pretty sure I could lug a smallish
weapon around on the back of a camel to take it to
the place I've stashed some scuds, if I didn't
want to drive a truck there.
Anybody catch Dale Bumpers on Charlie Rose
tonight? (Mon - Feb 25) This guy is a SENATOR?
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