BEIJING—The damage to the nuclear test site that North Korean leader Kim Jong Un has promised to shut down is more extensive than earlier assessments showed, according to a new study by a team of international scientists.
Space-based radar showed that after the initial impact of North Korea’s latest nuclear testin September last year, a much larger part of the Punggye-ri test site caved in over the following hours and days, according to a study published in Science magazine on Thursday. The study was conducted by researchers from Singapore, Germany, China and the U.S.
“This means that a very large domain has collapsed around the test site, not merely a tunnel or two,” said Sylvain Barbot, one of the authors who is an assistant professor at Nanyang Technological University in Singapore.
nuclear test site
Sea of Japan
The research feeds into an international debate over the value of Mr. Kim’s commitment to close the test site in the run-up to last month’s inter-Korean summit and his meeting with President Donald Trump, expected this month or early next.
Some U.S. officials and experts see the closure as a significant concession while others argue that the site is unusable and its dismantling is therefore an empty gesture designed to gain leverage in negotiations with Seoul and Washington.
Chinese seismologists involved in a study published last month concluded that a large part of the site was unusable due to the collapse of a cavity inside a mountain there, Mount Mantap, a few minutes after the last test.
U.S. researchers studying satellite imagery have since argued that, while tunnels may be severely damaged under Mount Mantap—where five of North Korea’s six nuclear tests took place—other parts of the Punggye-ri site are still usable.
Mr. Kim told South Korean President Moon Jae-in at their summit that two bigger tunnels at the site were still in good condition, according to Seoul’s presidential Blue House.
The last test caused an initial magnitude-6.3 earthquake, followed by a smaller tremor 8½ minutes later that was triggered by the collapse of damaged rock above the blast cavity, the Chinese study said.
The new study, which created three-dimensional images of the site, backs the Chinese researchers’ conclusion that a large part of the site can’t be used—while showing that the initial damage is “dwarfed” by the gradual collapse detected from space over the next few hours and days. That damage covers an area with a radius of 800 meters and a height of 400 meters, according to Mr. Barbot, who is also an adjunct professor at the University of Southern California.
“These findings make us infer that a large part of the Punggye-ri test site is inoperable and that further test may require a substantial investment in the construction of another facility elsewhere,” he said.
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