How scientists (including an SMU seismologist) monitor North Korea's nuclear tests

How SMU scientists are involved in monitoring North Korea's nuclear tests.

By Anna Kuchment
Staff Writer

At 9:30 p.m. Central time last Saturday, detectors around the world picked up signs of a massive explosion in the vicinity of North Korea's nuclear test site.  

The country claimed, for the second time in less than two years, that it had successfully detonated a hydrogen bomb, a weapon far more powerful than the bombs dropped on the Japanese cities of Hiroshima and Nagasaki during World War II.  

The last time North Korea said it had a hydrogen bomb, in January 2016, experts quickly dismissed its claim. This time, some say it's a possibility.  

"The magnitude of this event is bigger than any U.S. or Russian test since the early '70s," said Brian Stump, a seismologist at Southern Methodist University, which operates two seismic detectors for the Comprehensive Test Ban Treaty Organization. 

Shock waves from the explosion clearly registered on the SMU-operated detectors near Big Bend National Park in Texas and in Mina, Nev.  Here's what scientists know about the event — and how they know it.

How was this explosion different from North Korea's previous tests? 

It was much more powerful. North Korea's previous nuclear test, in September 2016, registered as a 5.3-magnitude tremor. Last weekend's explosion set off a 6.3-magnitude earthquake, according to the U.S. Geological Survey. 

"This event, in my mind, is at least an order of magnitude bigger than the event last year," said Stump. "It's a significant increase in yield."

There was also a smaller second event that followed 8.5 minutes after the first one, said Stump. He wonders if it was an aftershock or, perhaps, a sign of a tunnel collapse inside Mount Mantap, the mile-high peak inside which North Korea tests its nuclear weapons.


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