Study says test site has collapsed

Research by Chinese geologists shows the mountain above North Korea’s main nuclear test site has collapsed, rendering it unsafe for further testing and requiring that it be monitored for any leaking radiation.

The findings by the scientists at the University of Science and Technology of China may shed new light on North Korean President Kim Jong Un’s announcement that his country was ceasing its testing programme ahead of planned summit meetings with South Korean President Moon Jae In and US President Donald Trump.

Nuclear explosions release enormous amounts of heat and energy, and the North’s largest test in September was believed early on to have rendered the site in northeastern North Korea unstable.

Chinese authorities have said they’ve detected no radiation risk from samples collected along the border.

The data in the latest Chinese study was collected following the most powerful of the North’s six nuclear device tests, on September 3. The yield of the bomb was estimated at more than 100 kilotons of TNT, at least 10 times stronger than anything the North had tested previously. (The bomb the United States dropped on Hiroshima in 1945 had a yield of about 15 kilotons.)

The University of Science and Technology of China paper said the first of a series of earthquakes triggered by the blast was “an onsite collapse toward the nuclear test centre”. It said it was followed by an “earthquake swarm” in similar locations.

“In view of the research finding that the North Korea nuclear test site at Mantapsan has collapsed, it is necessary to continue to monitor any leakage of radioactive materials that may have been caused by the collapse,” the authors said in a summary on the university’s website. The study is peerreviewed and has been accepted for publication by the journal Geophysical Research Letters.