N.Korea nuke test relatively small-scientists By Michael Perry
SYDNEY, Oct 9 (Reuters) - North Korea's nuclear test on Monday might have been a "mini-nuke" explosion possibly as low as one kiloton, comparable to some small tests by India and Pakistan in 1998, scientists said on Monday.
The U.S. Geological Survey said it had detected a 4.2 magnitude quake in North Korea at 10:35 local time (0135 GMT) on Monday, confirming a similar report from South Korea.
Gary Gibson, senior seismologist at Australia's Seismology Research Centre, said a 4.2 magnitude quake would be the result of a one kiloton explosion.
"It depends on how the thing is set off. There is not a perfect correlation between magnitude and the yield and depends to some extent on the rock type they set it off in," he said.
"It is a relatively small nuclear test."
A U.S. intelligence source agreed that a preliminary examination of the data did not indicate a large blast or a series of explosions. But the source stressed that analysts were still working towards a definitive evaluation.
"It's premature because they're still evaluating the data," the source said.
The RIA news agency quoted on Monday Russian Defence Minister Sergei Ivanov as saying that the nuclear device tested by North Korea ranged between five and 15 kilotons.
The nuclear weapon the United States exploded over Hiroshima in 1945 produced a 12.5-kiloton yield.
In 1998, India carried out five underground nuclear tests at Pokharan in the western desert state of Rajasthan and declared itself a nuclear weapons state.
The total yield of the first round of blasts measured near 60 kilotons. Two days later, it exploded sub-kiloton devices that scientists said made it capable of conducting computer tests not covered by the Comprehensive Test Ban Treaty.
"Our biggest one was in the vicinity of 45 kilotons. That was thermo-nuclear," said S.K. Malhotra, head of the public awareness division of the Department of Atomic Energy.
Nuclear analyst Andrew Davies, from the Australian Strategic Policy Institute, said if the North Korean test yield was only a kiloton, Pyongyang may be disappointed.
"A kiloton is a very low yield and would tend to suggest, I would have thought, that the device was not all they hoped it would be," Davies told Reuters.
"If a nuclear, plutonium bomb fizzles, you can still get one or two kilotons quite easily. You still get a significant energy release. But an efficient device will give you more like 20 (kilotons)."
MINI NUKES
The United States has said it is interested in developing so-called "mini nukes" -- nuclear weapons with a yield of less of than five kilotons.
Indian nuclear scientists said they thought the North Korean test was an indication that the country was going for smaller devices to ensure effective delivery.
"They are concentrating more on the small devices because of reliability of launching and effectiveness," said A.N. Prasad, former chief of the Bhabha Atomic Research Centre, India's top nuclear research facility.
"If the situation demands, they can scale it up, which is not difficult. This is the best approach now."
After India exploded its devices, arch foe and neighbour Pakistan rushed to conduct its own tests.
Within days it had conducted six tests, although claims related to the number, strength and yield of the tests were doubted by scientists in India and the United States.
Pakistan said two nuclear tests had a total yield of between 34-48 kilotons, while three others were sub-kiloton. It said a sixth test yielded 10-15 kilotons.
The Southern Arizona Seismic Observatory said the two major tests yielded 9-12 kilotons, while the sixth yielded only 4-6 kilotons.
A source in Beijing who is close to the North Korean regime said Pyongyang had detonated a neutron bomb, designed to release larger amounts of deadly radiation than other nuclear weapons. There was no immediate confirmation of the claim. (Additional reporting by Krittivas Mukherjee in MUMBAI, Simon Cameron-Moore in ISLAMABAD, James Grubel in CANBERRA and David Morgan in WASHINGTON)
© Reuters 2007. All Rights Reserved.
According to South Korea-based Yonhap News service, and the Associated Press, North Korea has announced that it has successfully conducted its first nuclear test. 
Location of a 4.2 earthquake, allegedly caused by the nuclear test.
North Korea first announced it possessed nuclear weapons in 2005, though because it had not conducted a nuclear test its nuclear capability remained ambiguous. The United States, Japan, China, and South Korea have all urged North Korea to abandon its nuclear program. North Korea released a statement on October 3 saying that it would soon conduct a nuclear test, and also emphasized that it would neither use nuclear weapons first nor aid other countries in nuclear proliferation. The state claimed that it would only use the weapons as a deterrent against the United States and its allies. In 2003, U.S. President George W. Bush and South Korean President Roh Moo-hyun said that they "would not tolerate" a nuclear North Korea. China and Japan have also expressed concern.

U.S. officials have reported that the government of the People's Republic of China was given a 20-minute advance warning that the test was about to occur. The PRC sent an emergency alert to Washington through the United States embassy in Beijing and President George W. Bush was told shortly after 10 p.m. that a test was imminent by National Security Advisor Stephen Hadley.

Rumors of an impending nuclear test have circulated since North Korea announced its weapons capability. The Natural Resources Defense Council estimates that North Korea may have up to 10 or 12 nuclear devices already built.

According to North Korea's Central News Agency, the country conducted an underground nuclear test successfully without any radioactive leakage. Underground tests, if they fully contain the nuclear blast, can result in a minimum of nuclear fallout contamination. If confirmed, the nuclear test by North Korea would be the first nuclear test since the dual Indian and Pakistani nuclear tests of 1998.

The U.S. Geological Service has recorded a magnitude 4.2 event in eastern North Korea at 01:35:27 (UTC), or 10:35:27 North Korean local time.

U.S. President George W Bush speaking at the White House ahead of an emergency closed session of the UN Security Council called the action "unacceptable ... North Korea has defied the will of the international community and the international community will respond." He also described it as "a threat to international peace and security. The United States condemns this provocative act."

Bush contacted the leaders of Russia, China, Japan and South Korea, the other nations that have been engaged in negotiations with North Korea. All have already denounced the action. China using the harshest language yet against its old war time ally, calling the test "brazen". Japan's Prime Minister Shinzo Abe insisted on "decisive action."

Some experts are speculating that the test may push the United Nations to back sanctions against the North Koreans, Japan's U.N Ambassador Kenzo Oshima has told reporters in New York that the United States is drafting the resolutions, which could range from trade restrictions to monetary dealings and even a sea based blockade. The sitting members have strongly condemned the nuclear test.

In the first significant reaction to the announcement the South Korean government has decided to suspend a scheduled shipment of its emergency relief aid to its northern neighbor.  An official from the Unification Ministry said "A ship was scheduled to depart ... carrying 4,000 tons of concrete on Tuesday, but we decided to delay the shipment under the current circumstances."

The yield of the device has not been conclusively confirmed. Fox News has reported the yield at below 4 kilotons, citing a unspecified senior Bush administration official; however, Russian military sources estimate the yield as between 5-15 kilotons. The Korea Institute of Geoscience and Mineral Resources stated its estimate of the yield as 550 tons, but later scaled it up to 800 tons.

A senior seismologist at the Australian Seismology Research Centre said that a 4.2 magnitude quake would roughly correspond with a one kiloton explosion, but would not say it was conclusive, since it depends on the type of rock that the test was set off in.

It has been reported that the Korea Exchange, South Korea's main stock exchange, suspended trading for five minutes upon hearing news of the test.