Sources at Asahi and 38 North, the latter of which are major critics of the North Korean regime, recently reported that subterranean collapses close to North Korea's nuclear testing sites at Punggye-ri. What is more disturbing is that they could destabilize a large volcano in the region.
A tunnel recently collapsed causing the death of up to 200 construction workers near to the testing site. TV Asahi, a Japanese channel, recently reported on the incident that occurred on the 10th September. This was just one week following North Korea's sixth nuclear test under Mount Mantap.
TV Asahi reported that the received news of the collapse from an unnamed North Korean source. The anonymity of the source is not unprecedented given the strict media blackout of the North Korean regime. The sources for TV Asahi are very familiar with the situation in North Korea who indicated that the collapse happened during recent construction of a tunnel close to the nuclear test site in the northeast of North Korea.
Although it is unclear whether the collapse is directly related to the explosion of an apparent Hydrogen bomb it is certainly causing international concern. The hydrogen bomb test is thought to have been 10 times more powerful than the bomb dropped on Hiroshima.
North Korea's recent bomb test caused a 6.3 magnitude tremor sparking fears that surrounding ground could be destabilized. It had initially been reported by the USGS that the termor was a magnitude 5.6 at 10km depth. This was later upgraded to the now commonly quoted 6.3 magnitude at 0km depth.
The smaller quake also appears to occur at a 0km depth in North Hamgyong province, where the nuclear test site is located, according to South Korea's meteorological agency. The USGS also believes it occurred at the site, though at a depth of probably 5km.
South Korean experts said the specific soundwaves could not have been man-made. China's Earthquake Administration also believes it had characteristics of a natural tremor. Analysts from the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), the UN-backed monitoring group, said the quake was "unlikely man-made".
The more serious fear is that the nearby Mount Peaktu, a dormant volcano, has started to experience landslides and aftershocks. Could the tests lead to an eruption of the volcano in future?
Hundreds were killed
South Korean experts said that the specific sound waves caused by this smaller quake were not recorded. China, however, believed the termors had features of a natural quake rather than one associated with man-made activities. International nuclear test monitors held the same view.
Of course, North Korea has made no comments on the incidents,
A week later a new tunnel was being dug under the mountain, perhaps to replace the first collapsed one. This second tunnel also collapsed. TV Ashai, quoting North Korean sources, reported that 100 workers were killed by the collapse with a further 100 killed in a rescue attempt.
“raising the possibility that more than 200 people died together,” stated the TV Asahi.
As you would expect, the incident is yet to be confirmed by North Korea.
The recent spout of nuclear tests likely played a part in the disaster, it is believed by an analyst from 38 North. The analyst spoke to IFLScience several days ago about the recent collapses.
Was the cause nuclear testing?
38 North are strong critics of the North Korean regime and they suggest the recent nuclear test was the primary cause.
"The aftershocks [after North Korea's sixth nuclear test] could well have caused tunnel collapses," the Analyst said.
"From past experience, we know that the North Koreans do not waste much time going back into areas where previous tests were conducted," he continued.
Despite the recent nuclear tests potentially destabilizing the region, there is little sign Kim Jong-Un and his regime will abandon the test site. Even given the clear indication that the area is becoming unsafe for future testing.
A large cavity, up to 60 meters across, under the mountain could also leak large amounts of radiation if testing resumes according to South Korea's Meteorological Agency. What is more, the increasing weakening of structural integrity of the region could lead to a volcanic eruption as well.
A very tired mountain
Others also suggest that Mount Mantap could be suffering what is called "tired mountain syndrome". This, although a funny sounding term, is actually quite serious. It means the structural geology of the area could have been seriously altered by the testing. North Korea's nuclear testing might have weakened the strength of subsurface geology, especially fracturing and maybe faulting.
News of this incident comes less than two weeks after The Washington Post recently reported on the "tired mountain syndrome" of the region.
“What we are seeing from North Korea looks like some kind of stress on the ground,” Columbia University seismologist Paul G. Richards told The Washington Post. “In that part of the world, there were stresses in the ground, but the explosions have shaken them up.”
Chinese experts are also concerned. They have also warned that further testing could cause the mountain to collapse and release large amounts of radiation.
The final word
Whether this will actually mean an increased likelihood of a volcanic eruption in the future, it is not yet clear. 38 North noted that “abandonment of the site for nuclear testing should not be expected."
Whatever the case may be, the recent tunnel collapses and increase in landslides and aftershocks is not a good sign. The future will tell if Kim-Jong Un and his regime take heed of warnings about the stability of the region.