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2010/01/10 11:15 KST
(LEAD) N. Korea's 2nd nuclear test site pinpointed in new study

By Sam Kim
SEOUL, Jan. 10 (Yonhap) -- Two U.S.-based scientists said Sunday they've located the site of North Korea's second nuclear test last year more precisely than ever before, pinpointing it just 2 kilometers off the place where the first test was conducted in 2006.

   Lianxing Wen, a geophysics professor at the State University of New York in Stony Brook, and his graduate student, Hui Long, located the epicenter of the second nuclear test on May 5 last year with a margin of error of only 140 meters, compared with 3.8 kilometers achieved by the U.S. Geological Survey.

   "We locate the 2009 test at 723 meters north and 2,235 meters west of the 2006 test," the scientists said in the study, which was published in the January-February edition of Seismological Research Letters of the Seismological Society of America.

   Identifying the coordinates of the 2009 test site as 41°17′38.14″N latitude and 129°4′54.21″E longitude, the scientists said their findings should help Asian monitors to pinpoint the location of another nuclear test should North Korea ever decide to go ahead with one.

   "The location of any future nuclear test around this particular test site will be pinpointed in real time, with a similar precision," Wen said in a separate email interview. "With its exact location known, the wave propagation effects due to location geology can be accurately accounted for, leading to a more accurate determination of yield."

   North Korea conducted its first underground nuclear test in Oct. 9, 2006 in Punggye-ri in its northeastern county of Kilju, according to U.S. and South Korean officials.

   Wen and Long said they analyzed the seismic waves from the first nuclear test to understand the geological complexities of the earth in the region, and used the data to reduce the uncertainty involved in determining the ground zero of the second test.

   "The strategy is not to try to fully understand the complexities of the jungle (earth), but to take advantage of the forensic evidence of the jungle complexities that are imprinted in the recordings" of the first nuclear test, the scientists said in a separate introduction to their thesis.

   The waveforms from the first test were obtained from nine seismic stations based in Japan, South Korea and China, the study said.

   North Korea conducted its second nuclear test amid a deadlock in international talks aimed at stripping it of its nuclear ambitions, raising tensions and inviting harsh U.N. sanctions.

   "High-precision location would reveal, in real time and at great accuracy, an increasingly complete view of the geographic network of a nation's nuclear test infrastructure," the paper said.

   "Logistically and economically, it is convenient to use the same facilities to do multiple tests. Environmentally, it would confine nuclear wastes in a particular site," Wen said in the email.

   North Korea has in recent months toned down its belligerent rhetoric and hinted that it is willing to return to multinational talks over its nuclear weapons programs. South Korean defense officials say the communist country continues to operate nuclear-related facilities, including underground bunkers, in Kilju.

   Both Wen and Long are Chinese citizens.