North Korea’s nuclear test site is largely unusable

Kim Jong-un’s vow to halt nuclear testing sparked hopes he was committed to denuclearisation. Maybe we celebrated too soon.

Satellite imagery of the Punggye-ri nuclear test site in North Korea: the red circles indicate landslides. Picture: 38North.

A large part of North Korea’s underground nuclear test facility, which leader Kim Jong-un pledged to close, is unusable anyway due to the collapse of a cavity inside the mountain after the last blast there, Chinese scientists say.

Seismologists involved in a soon-to-be-published study also warned that another blast in the same spot and with similar yield could cause “environmental catastrophe.”

Another study led by Chinese seismologists and published this month also concluded that a secondary tremor shortly after the blast was caused by the cavity’s collapse, but didn’t judge whether the Punggye-ri test site could still be used.

Mr. Kim said last week he was suspending nuclear and missile tests and closing the Punggye-ri facility, where all six of his country’s nuclear tests took place. His announcement was welcomed by the U.S., South Korea and China as a positive step in the run-up to an inter-Korean summit on Friday and a planned meeting between Mr. Kim and US President Donald Trump by June.

US officials and North Korea watchers, however, are debating how meaningful Mr. Kim’s moves are. Some see them as major concessions and others, arguing that Punggye-ri is unusable, call them empty gestures designed to gain leverage with Washington and Seoul while remaining determined to retain his nuclear weapons.

During his announcement last week, Mr Kim hinted he wouldn’t be giving up nuclear weapons. He celebrated the completion of his nuclear-missile program, calling it a “miraculous victory” that had been “perfectly accomplished…in a short span of less than five years.”

And while Mr Kim also pledged not to carry out further long-range missile tests, he made no mention of shorter-range missiles that would be capable of striking US allies in South Korea and Japan.

Soon after the sixth and largest blast last September, satellite images suggested that one part of the site, a 7,200 foot granite peak called Mount Mantap had diminished in height. Some US and South Korean experts suggested that tunnels inside the mountain—where five of North Korea’s six nuclear tests took place—had collapsed, rendering much of the site useless.

Now, the two Chinese studies give credence to that theory. They both used data from seismic monitoring stations in China and abroad to analyze the initial 6.3-magnitude tremor caused by the blast and another smaller tremor 8½ minutes later.

Both studies concluded that the second tremor, of 4.1-magnitude, was caused by the collapse of damaged rock above the blast cavity inside the mountain, rather than another explosion or a shift in tectonic plates.

“The occurrence of the collapse should deem the underground infrastructure beneath mountain Mantap not be used for any future nuclear tests,” said an abstract for the first study, led by researchers at the University of Science and Technology of China, or USTC.

Past tests caused previously inactive tectonic faults in the area to reach a state of “critical failure,” according to the abstract presented at a meeting of the American Geophysical Union in December, which was posted to the group’s website.

The researchers warned that a nuclear test of similar yield to September’s “would produce collapses in an even larger scale creating an environmental catastrophe,” according to the abstract.

Punggye-ri is less than 80 km (50 miles) from the Chinese border, and Beijing has been ramping up its monitoring for radioactive fallout in recent years, out of concern, analysts have said, that contamination could provoke a public outcry and force the government to harden its approach to Pyongyang.

Chinese officials have said that no contamination has been detected so far in the aftermath of the tests.

The USTC study was accepted on Monday for publication in the American Geophysical Union’s journal, Geophysical Research Letters, according to a statement on USTC’s website. A spokesperson for that journal said the paper would be published on its website in the next few days.

A USTC official said the two lead authors couldn’t comment because of the sensitivity of the subject, and referred questions to their supervisor and co-author, Wen Lianxing, a seismology professor at Stony Brook University in New York.

Prof. Wen said the version to be published in Geophysical Research Letters wouldn’t include the wording about Mount Mantap being unusable for future tests, and the potential environmental catastrophe if it was. He didn’t respond when asked why those words had been removed.

The second study was published in the same journal this month and was conducted by two researchers from universities in Greece and the Czech Republic and four Chinese seismologists, including three attached to the government’s China Earthquake Administration.

That study said modeling showed that “the explosion created a cavity and a damaged ‘chimney’ of rocks above it.” The study estimated the size of the blast cavity at 1 million cubic meters and said the aftershock wasn’t caused by a second explosion, or a tectonic earthquake but by “a rock collapse, or compaction, for the first time documented in North Korea’s test site.”

The study didn’t say whether the site was still usable.

One co-author, Professor Li Li of the China Earthquake Administration’s Institute of Geophysics, said in a telephone interview that she thought it is possible that the site could be used for further tests. But she said that the other Chinese study explored the issue in greater detail.

North Korea experts at the Johns Hopkins University’s US-Korea Institute published a commentary on Monday arguing that the Punggye-ri test site was still fully operational.

The area at Mount Mantap was apparently abandoned but two other parts appeared to be ready for further tests, said the commentary on the institute’s 38 North website.

“Whether that will stay an option will depend on reaching verifiable agreements that build on Pyongyang’s pledge to shut down the facility,” it said.

The Wall St Journal