The single mountain under which North Korea most likely conducted its five most recent nuclear bomb tests, including the latest and most powerful on Sunday, could be at risk of collapsing, a Chinese scientist said. By measuring and analyzing the shock waves caused by the blasts, and picked up by quake stations in China and neighboring countries, researchers at the University of Science and Technology of China in Hefei, Anhui province, said they were confident that they were all carried out from under the same mountain at the Punggye-ri test site. The team from the seismic and deep earth physics laboratory made the claim in a statement posted on their website on Monday. Its leader, geophysicist Wen Lianxing, said that based on data collected by more than 100 earthquake monitoring centers in China, the margin of error was no more than 100 meters. Wang Naiyan, the former chairman of the China Nuclear Society and senior researcher on China's nuclear weapons program, said that if Wen's findings were reliable, there was a risk of a major environmental disaster.

Another test might cause the whole mountain to cave in on itself, leaving only a hole from which radiation could escape and drift across the region, including China, he said. "We call it 'taking the roof off'. If the mountain collapses and the hole is exposed, it will let out many bad things." Sunday's blast was followed by an earthquake eight minutes later, which China's seismic authorities interpreted as a cave-in triggered by the explosion. Not every mountain was suitable for nuclear bomb testing. Wang said, adding that the peak had to be high, but the slopes relatively flat. More from the South China Morning Post: North Korea tests nuclear bomb it says can be made into warhead for long-range missile How China responded to previous North Korean nuclear tests China and Russia unite against North Korean nuclear test Based on the fact that North Korea has a limited land area and bearing in mind the sensitivity of its nuclear program, it most likely does not have too many suitable peaks to choose from.

How long the mountain would continue to stand would also depend on where the North Koreans placed the bombs, Wang said. "If the bombs were planted at the bottom of vertically drilled tunnels, the explosion would do less damage," he said. But vertical tunnels were difficult and expensive to build, and it was not easy to lay cables and sensors to collect data from the explosion, he said. Much easier was to bore a horizontal tunnel into the heart of the mountain, but this increased the risk of blowing off the top, he said.