Mount Mantap, a 2,205-meter peak about 115 kilometers southeast of Mount Paektu, is the heart of North Korea's nuclear weapons program. North Korean troops dug tunnels hundreds of meters into the mountain horizontally, built detonation chambers at their ends and put support facilities on the surface. This is the Punggye-ri nuclear test site in Kilju County, North Hamgyong Province. Mount Mantap originally belonged to the Mount Paektu volcanic belt, but there is no record of an earthquake or volcanic eruption there since Koreans first settled the region. The mountain itself consists largely of hard granite formed in the Mesozoic era, and its underlying bedrock dates to the Precambrian, more than 541 million years ago, making it stable.
Yet even solid granite Mount Mantap has now partly collapsed, and the strata beneath it are unstable. The cause is six nuclear tests conducted between October 2006 and September 2017. The atomic bomb dropped on Hiroshima had a yield of about 15 kilotons; North Korea's first through sixth tests ranged from as little as 0.8 kilotons to as much as 50 kilotons. They triggered artificial earthquakes of magnitude 3.9 to 5.7, felt not only across the Korean Peninsula but as far as China and Russia.
A joint South Korean-Chinese research team recently found that those tests awakened dormant fault lines around Mount Mantap and have made earthquakes frequent there. According to the team, 1,399 earthquakes have occurred in the Punggye-ri area as a result of the tests. The quakes were concentrated along fault lines running north-northwest over a length of 24 kilometers. If those faults were activated simultaneously, the team said, they could produce a magnitude 6.4 quake.
Earlier, a South Korean study published in 2016 warned that an artificial earthquake of magnitude 7.0 or higher caused by a Punggye-ri test could trigger an eruption of Mount Paektu, an active volcano holding an enormous body of magma. An eruption would bring immediate damage to neighboring countries from volcanic ash and flooding, and in the worst case could set off a "volcanic winter." A volcanic winter is a global plunge in temperatures caused by ash and toxic gases blanketing the atmosphere. How long can such warnings, sounding ever more often, be ignored?
