Research finds North Korea's nuclear site unusable

North Korea's main underground nuclear test site collapsed following a bomb blast last year, making it unusable for further tests and requiring monitoring for radioactive leaks, according to research by Chinese seismologists.

The North's leader, Kim Jong Un, announced last week Pyongyang would halt nuclear and ballistic missile tests ahead of planned summit meetings with South Korean President Moon Jae-in and US President Donald Trump. The research findings may provide insight into why North Korea has offered to stop nuclear tests.

North Korea tested five of its six nuclear bombs at the Mount Mantap test site in the country's northeast near the border with China.

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A September 3 test that North Korea claimed was a hydrogen bomb triggered a series of earthquakes in and around the Mount Mantap test site, with an aftershock eight-and-a-half minutes later causing an "onsite collapse toward the nuclear test center," said researchers at the University of Science and Technology of China.

"The occurrence of the collapse should deem the underground infrastructure beneath mountain Mantap not be used for any future nuclear tests," the researchers said in an abstract. "The triggered earthquake swarm indicates that North Korea's past tests have altered the tectonic stress in the region to the extent that previously inactive tectonic faults in the region have reached their state of critical failure."

The peer-reviewed study was accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

The researchers found that any further high-yield nuclear tests would produce an even larger collapse "creating an environmental catastrophe." They said that it was necessary to monitor possible radioactive leaks caused by the mountain collapse.

The Mount Mantap test site is less than 100 kilometers (60 miles) from the border with China, and nuclear tests have caused concern in Beijing and border communities.

Previous studies and news reports have also indicated a partial collapse at Mount Mantap.

cw/kms (AFP, AP, Reuters)

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