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Scientists study North Korea’s nuclear tests, and the earthquakes

Earthquake Studies Reveal the True Cost of North Korea’s Nuclear Tests Inverse,  By Emma Betuel September 26, 2018
On September 3, 2017, North Korea tested a nuclear bomb 17 times larger than the one that leveled Hiroshima, sending ripples of alarm across the world. More than just raise the eyebrows of policy makers, the blast also piqued the interest of experts at Columbia University’s Lamont Doherty Earth Observatory, who show in a pair of recent papers that last September’s nuclear test may be responsible for many of the aftershocks that occurred in the past year.

While some existing research argues it’s unlikely that a nuclear test could cause a massive earthquake, the two papers identify 13 high-frequency tremors that traveled through North Korea in the months following the September test. More importantly, they confirm which of them were triggered by the explosion, which were unrelated earthquakes, and which — as some have feared — were caused by additional nuclear tests.

“North Korea has conducted six nuclear tests, but the latest one was huge. That’s what we’ve analyzed the signals from,” Woon Young Kim, Ph.D., the lead author of the Seismological Research Letters paper and a professor of seismology geology and tectonophysics, tells Inverse. “The question was: Were they explosions or were they earthquakes?”

The earliest rumblings occurred just eight minutes after the initial nuclear test but were not included in the paper’s aftershock count. But two occurred later that month and another on October 12. In December there were five more. The tremors continued into 2018, with four in February and the final one on April 22.

The issue, explains Kim, is that scientists were aware of these tremors as they occurred but nobody knew why they were happening. At the time, some expertsidentified these tremors as evidence that North Korea was testing more nukes on a smaller scale, but Kim’s new paper, published in conjunction with another studyauthored by his colleague David Schaff, Ph.D., suggests not only that some of those tremors were actually just earthquakes but also that they were tightly grouped along a fault line, where similar events will likely occur in the future.

Bomb or Earthquake?

To find out whether these shakes were organic or the result of nuclear testing, Kim analyzed two major wave types measured after the tests. Whenever the earth shakes (whether it’s due to an explosion or not), the first rumble to roll by is called an “P-wave” or primary wave. It’s typically the first wave to get picked up by monitoring stations and travels around six kilometers per second.

…….. After more analysis, the researchers concluded that “event 8” was actually an earthquake, together with two other suspected explosions.

“There have been about three events at the North Korea test site that we feel were misclassified,” Schaff tells Inverse. “No method is 100 percent certain, but combining the two methods, I was able to say with a very high probably of certainty that these were earthquakes.”

The Real Consequences of September 3, 2017

The good news is that these results suggest that North Korea isn’t testing bombs as frequently as some might fear They do, however, suggest that there could be something going on underneath the surface as a result of the September 3 explosion.

Using the data provided by Kim, Schaff showed that the tremors following the explosion were clustered along a unified path. As it turns out, what had originally looked like a random spattering of explosions and earthquakes over an area spanning five kilometers was actually a cluster of tremors that occurred within about 700 meters of one another near North Korea’s Chinese border.

The activity around this fault line can actually be traced back to that initial explosion in September of last year, explains Kim. “It’s not 100 percent sure, but I think somehow that the nuclear test was so large that it triggered these small seismic events to the north of the area,” he says.

As some have feared, it appears that North Korea’s testing hasaltered the landscape, at least near the surface of the Earth. In April, Kim Jong-Un announced that North Korea would stop testing nukes in its mountainous hideaway beneath Mt. Mantap, a move that Chinese scientists have suggested is due to the fact that a number of underground tunnels have collapsed beneath the mountain. Other studies have also suggested that continued testing has blown bits of Mt. Mantap to smithereens, making it a non-useful test site.

Should North Korea start testing again, says Schaff, he will be eager to continue the project. “It’s nice to be working on something that affects the state of the world we’re living in,” he says. “This is more than just knowledge for knowledge’s sake.  https://www.inverse.com/article/49304-north-korea-nuclear-test-caused-earthquakes

September 28, 2018 - Posted by Christina Macpherson | environment, North Korea, safety, weapons and war