N. Korean nuclear blast probably less powerful than hoped for: Yale scholar

SEOUL, May 28 (Yonhap) -- North Korea apparently failed to achieve desired explosiveness in its second nuclear test, a Yale University professor says, citing seismic readings that have been generated by it.

North Korea set off an underground nuclear explosion on Monday, creating a shock that registered 4.52 in magnitude on the Richter scale, according to a Vienna-based anti-nuclear weapons organization.

North Korea produced a magnitude of 4.1 in its first test in October 2006, the Comprehensive Nuclear-Test-Ban Treaty says.

Jefferey Park, director of the Yale Institute for Biospheric Studies, said the seismic data from Monday's test indicate that North Korea failed to create a "Hiroshima-class crude explosive device."

"It was too small," he wrote on the Bulletin of the Atomic Scientists, referring to the explosion.

Using what he called standard conversions, Park, a geologist, said North Korea appears to have produced a force of 4 kilotons or less through the test that took place in the northeastern region.

"That's a lot of energy, much larger than the 2006 North Korean test, but it still falls far short of an expected 12-20 kiloton yield of a crude Hiroshima-style device," he said. North Korea is believed to have produced less than 1 kiloton in its previous test.

Park said if North Korea had built a detonator precise enough, it would have obtained a yield of 10-20 kilotons. One kiloton is equal to 1,000 tons of TNT.

"My guess is that North Korea tried and failed to get a simple plutonium bomb to detonate correctly," he said.

But he said the latest explosion should not be taken as a failure, warning, "Make no mistake -- an inefficient nuclear weapon is nothing to dismiss."

"Even at the low end of its estimated yield (2 kilotons), the May 25 test released as much or more explosive energy than the largest conventional-explosive air raids during World War II," he said.

Well, not as far as I could throw him:

http://earth.geology.yale.edu/~jjpark/

I am originally from Orange County, California. My interest in the earth sciences began began after the 1971 earthquake in Sylmar, California tossed me from my bed. I was introduced to plate tectonics the following year and was hooked on earth science for life. I received my Bachelor of Science Degree in Physics from Princeton University in 1979, where I worked as a go-fer in the geology department. I gave my first talk at an AGU meeting in 1980, arguing against a theory that large earthquakes could cause observable changes in the Earth’s rotation axis. I received my Doctorate in Earth Sciences in 1985 from the University of California, San Diego. From 1985-1986, I did a post doc at Princeton University and from 1986 I have been on the faculty of Yale University.

more about Park:
http://earth.geology.yale.edu/people/moreinfo.cgi?netid=jjpark

-another source-

Russians overestimate power of North Korean blast ... again
Peter Alford
May 28, 2009
The Australian
http://www.theaustralian.news.com.au/story/0,25197,25547657-25837,00.htm

NORTH Korea’s nuclear explosion on Monday was far smaller than the initial estimate. The maximum likely yield of the North Korean device was four kilotons (the explosive equivalent of 4000 tonnes of TNT) or less, according to the emerging scientific consensus, rather than the 10-20 kilotons estimated on the day by the Russian Defence Ministry.

From KCNA News Agency:

CPRK Regards S. Korea’s Full Participation in PSI as Declaration of War against DPRK

Pyongyang, May 27 (KCNA) — The Lee Myung Bak group of south Korea keen on the moves for confrontation and war against the DPRK in league with foreign forces on May 26 officially declared at last it would fully participate in the PSI despite the unanimous opposition of all Koreans and public opinion at home and abroad.

The Committee for the Peaceful Reunification of Korea issued a statement on May 27 in this regard.

It said:

The so-called PSI is a mechanism for a war of aggression built by the U.S. against the DPRK under the pretext of intercepting and blockading ships and planes, etc. suspicious of transporting weapons of mass destruction including nuclear weapons and missiles.

The PSI has been criticized and repudiated at home and abroad for its aggressive nature and illegality.

Moreover, full participation in the PSI by a side on the Korean Peninsula where the state of military confrontation is growing acute and there is constant danger of military conflict itself means igniting a war.

The DPRK, therefore, has already seriously warned the south Korean authorities against the above-said moves and repeatedly clarified its stand that it would strongly counter those moves of the Lee group, in particular, regarding them as a declaration of a war as it is pursuant to its American master’s policy.

Nevertheless, the Lee group undisguisedly took a step of fully participating in the PSI, which former regimes dared not do so, bringing the situation on the Korean Peninsula and inter-Korean relations beyond the uncontrollable danger line of a war.

It is preposterous for the Lee group to have opted to fully participate in the PSI under the pretext of the underground nuclear test of the DPRK for self-defense.

It is nothing strange and quite natural for a nuclear weapons state to conduct a nuclear test.

The anti-DPRK racket kicked up by the U.S. and its followers under that pretext is not truly aimed at the nuclear non-proliferation but prompted by their black-hearted intention to stifle the DPRK.

Now that the south Korean puppets were so ridiculous as to join in the said racket and dare declare a war against compatriots through their full participation in the PSI, the DPRK is compelled to take a decisive measure, as it has already warned.

The DPRK solemnly declares as follows in view of the prevailing situation:

First, The DPRK will deal a decisive and merciless retaliatory blow, no matter from which place, at any attempt to stop, check and inspect its vessels, regarding it as a violation of its inviolable sovereignty and territory and a grave provocation to it.

Second, The DPRK will take such a practical counter-action as in the wartime now that the south Korean authorities declared a war in wanton violation of its dignity and sovereignty by fully participating in the PSI.

The DPRK will never pardon the south Korean puppet group of traitors for going mad with confrontation and war, bereft of any reason as servants for outside forces in the moves for a war of aggression.

The Lee Myung Bak group will be held wholly accountable for the disastrous consequences to be entailed by its reckless hostile acts against the DPRK.

More specifically, the active US arsenal at the moment has -

ICBM -

200 W78 on Minuteman, each 350 kilotons
300 W87 on Minuteman, each 475 kilotons

SLBM -

768 W76 on Trident, each 100 kilotons
384 W88 on Trident, each 475 kilotons

Airborne -

528 W80 on ALCM, each 5-150 kilotons (choice)
140 B61 gravity bomb, each 0.3-340 kilotons (choice)
100 B83 gravity bomb, each 5 kiloton - 1.2 megaton

All the air launched types are "dial a yield", variable power weapons that can be set low as tactical weapons or full as strategic ones. ALCMs are air launched cruise missiles. There are reserve warheads in addition to the above deployed totals, and another 500 or so theater-tactical weapons active, cruise missile or B61 gravity bombs.

Arms control agreements have led to most MIRVing being eliminated (as creating too much incentive to first strikes, a dubious proposition); Tridents that can carry 8-12 warheads only carry 4, and Minuteman that can carry 3 generally carry 1 (a few 2). Manned bombers can carry up to 20 ALCM each but typically have much less than their theoretical load.

The emphasis in the modern arsenal is all on minimum physical size and maximum accuracy. The error probable circle of the W88 on the Trident is 90 meters, for example, meaning half of all shots are expected to land within that distance of the aim point. Putting half a megaton on a specific city block is more than enough for silo-busting. 2/3rds of the sub missiles retained are deliberately softer W76s.

We simply don't use high megaton weapons anymore. Those things left the force in the late 1960s as missiles took over from manned bombers.

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