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2006-10-10 China-Japan-Koreas

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Posted by john 2006-10-10 17:30|| || Front Page|| [4 views since 2007-05-07] Top

#1 Seismologists are using equations of the form

Mb = a + b log(Yield in kT)

For the Nevada test site

Mb = 3.92 + 0.81 log Y

These attenuation coefficients come from testing known yield weapons (yield known from previous atmiospheric test) at the test range. They depend on the rock found at the test site.

For the Kazakstan site

Mb = 4.45 + 0.75 log Y

The US detonated an 80 kiloton nuclear device in the Aleutian Islands to simulate the geological conditions of the Soviet test site. Using the formula above, the measured seismic magnitude of 5.9 would correspond to a yield of 85 kilotons, in good agreement with Longshots known yield of 80 kilotons.

Now, it appears they are using

Mb = 4.262 + 0.973 Log Y

Without any knowledge of the NoKo geology or having any calibration test.

They are pulling these coefficients out of thin air. This is shoddy science.
Change the coefficients slighly and you suddenly get 10 kT yield, rather than 0.5kT.

Add the fact that NoKo used an old mine, where a huge cavity would be available.

(in the 1970s) Albert Latter, of the RAND Corporation, presented preliminary findings on the principle of cavity decoupling --- the explosion of a bomb in an underground cavity large enough that the surrounding rock would not deform plastically (permanently) in any direction, but remain elastic. Under such conditions, according to Latter, the seismic signal could be reduced by a factor of as much as 300, thereby rendering impossible the detection of all but the very largest tests

None of these "experts" have a clue about the real yield of the test.
All talk of "fizzle" is just speculation

Posted by john 2006-10-10 17:50|| 2006-10-10 17:50|| Front Page Top

#2 That's my understanding as well, John. And that means that seismic data alone do not tell us much, including whether this was a small nuclear blast, a failed blast or (improbable but not ruled out by the public data I've seen so far) a deliberately deceptive conventional blast.

Posted by lotp 2006-10-10 18:10|| 2006-10-10 18:10|| Front Page Top

#3 john I am at a loss for words after that

Posted by sinse 2006-10-10 18:18|| 2006-10-10 18:18|| Front Page Top

#4 According to Dr R. Chindambaram (who has actually tested a series of nuke weapons)..

the strength of the seismic signal is determined by the way the explosive energy couples into the geological medium, and there are strong regional differences. In fact, each seismic station has to be calibrated, and this is obvious from the range of seismic magnitudes reported by various global seismic stations. A small difference in body wave magnitude of a little over 0.2 corresponds to a halving of the yield estimate. And for any underground nuclear explosion, seismic body wave magnitudes are known to range over 1.0 or even more, which indicates the pitfalls in yield estimates from seismic signals, unless they are done carefully and correctly.

Posted by john 2006-10-10 18:20|| 2006-10-10 18:20|| Front Page Top

#5 From a CTBT paper

For US announced tests, the equation for the line is:
mb = 3.92 + 0.81 log Y(kt) (Murphy, 1981)
For the Nevada Test Site and other areas of the world with similar geological conditions, we can use this equation to convert between magnitude and yield
Unfortunately, we cannot necessarily apply this formula to every area, because different regions transmit seismic waves with different efficiencies.
In the western United States there are high temperatures in the upper mantle, and the continent is being pulled apart by plate tectonic motion. Seismic waves travelling through such tectonically active areas are greatly attenuated (their amplitude is reduced), thus producing a relatively small seismic signal.
For tectonically stable areas such as eastern North America and Central Asia (including the Soviet Unions old test site in Kazakhstan), the relationship between magnitude and yield is:
mb = 4.45 + 0.75 log Y(kt) (Ringdal et al., 1992)

So, these geniuses are using Soviet Shagan test site coefficients (tectonically stable region) in the Pacific rim (hardly).

And the press laps this all up...

Posted by john 2006-10-10 18:26|| 2006-10-10 18:26|| Front Page Top

#6 And meanwhile it appears there is no evidence at all that any nuclear fission was actually achieved.

Posted by lotp 2006-10-10 18:27|| 2006-10-10 18:27|| Front Page Top

#7 Since smaller yields are less likely to fuse the surrounding rock and contain the fission products, some venting is expected (unless that mine is really deep).
Atmospheric sampling should pick up traces of the Pu.

One interesting suggestion is that the purity of the NoKo Pu is quite low.. it is essentially little better than reactor grade stuff (which would give a low yield).

Posted by john 2006-10-10 18:37|| 2006-10-10 18:37|| Front Page Top

#8 Are you sure the venting isn't Kimmy's flatulance?

Posted by BigEd 2006-10-10 19:02|| 2006-10-10 19:02|| Front Page Top

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