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14:50 09Oct2006 RTRS-NK explosion equals several hundred tons of TNT-US

WASHINGTON, Oct 9 (Reuters) - An underground explosion equal to several hundred tons of TNT appears to be responsible for a"seismic event" detected near a suspected nuclear test site in North Korea, a U.S. official said on Monday.
It could take several days for intelligence analysts to determine whether the event was the result of an unsuccessful nuclear test, a small nuclear device or a non-nuclear explosion, said the official who spoke on condition of anonymity.
North Korea announced earlier on Monday it had successfully conducted a nuclear test.
"If it was a nuclear test, it appears to be more of a fizzle than a pop," the official said, calling it"a seismic event... that would suggest an underground explosion."
"In terms of yield, we have it registering at less than four on the Richter scale. That's the kind of thing that could be the result of several hundred tons of TNT, rather than a nuclear test," the official added.
The U.S. Geological Survey said it had detected a 4.2 magnitude tremor in North Korea at 10:35 local time (0135 GMT).
Seismic data alone is unlikely to produce a definitive conclusion about what occurred, and U.S. analysts hope to receive useful evidence from atmospheric and radiological tests and other intelligence.
((Reporting by David Morgan; editing by Lori Santos; david.morgan.reuters.com@reuters.net; +1 202 898 8326))
Keywords: KOREA NORTH USA INTELLIGENCE