‘ Tired mountain syndrome’? NKorean tests may cause it

TOKYO — Have North Korea’s nuclear tests become so big that they’ve altered the geological structure of the land? Some analysts now see signs that Mount Mantap, the 7,200-foothigh peak under which North Korea detonates its nuclear bombs, is suffering from “tired mountain syndrome.”

The mountain visibly shifted during the last nuclear test, an enormous detonation that was recorded as a 6.3 magnitude earthquake in North Korea’s northeast. Since then, the area, which is not known for natural seismic activity, has had three more quakes.

“What we are seeing from North Korea looks like some kind of stress in the ground,” said Paul G. Richards, a seismologist at Columbia University’s Lamont-Doherty Earth Observatory. “In that part of the world, there were stresses in the ground, but the explosions have shaken them up.”

Chinese scientists already have warned that further nuclear tests could cause the mountain to collapse and release the radiation from the blast.

North Korea has conducted six nuclear tests since 2006, all of them in tunnels burrowed deep under Mount Mantap at a site known as the Punggye-ri Nuclear Test Facility. Intelligence analysts and experts alike use satellite imagery to keep close track on movement at the three entrances to the tunnels for signals that a test might be coming.

After the latest nuclear test, on Sept. 3, Kim Jong Un’s regime claimed that it had set off a hydrogen bomb and that it had been a “perfect success.”

Analysts and many government officials said the size of the earthquake the test generated suggested that North Korea had detonated a thermonuclear device at least 17 times the size of the American bomb dropped on Hiroshima in 1945.

It registered as an artificial 6.3 magnitude earthquake, so big that it shook houses in northeastern China. Eight minutes later, there was a 4.1 magnitude earthquake that appeared to be a tunnel collapsing at the site.

Images captured by Airbus, a space technology company that makes Earth-observation satellites, showed the mountain literally moving during the test. An area on the peak visibly subsided.

The “tired mountain syndrome” diagnosis was previously applied to the Soviet Union’s atomic-test sites.