North Korea test around 31-times more seismic energy than previous tests

ANCHORAGE (KTUU) – Alaskan seismologists say the latest North Korean nuclear test produced around 31-times more seismic energy than their second largest test.

Matt Gardine, a seismologist with the Alaska Earthquake Center, says they recorded a 5.3 magnitude seismic event during that test September 9, 2016.

Saturday’s test was recorded as a 6.3 magnitude seismic event by both the Alaska Earthquake Center and the National Tsunami Warning Center.

Gardine explains there is not a one-to-one correlation as magnitudes increase.

Although 6.3 is only one whole number higher than 5.3, this blast released around 31-times more seismic energy.

Meaning, the kilotonnage of this device was likely a lot higher than North Korea used in previous tests.

When asked if seismologists could tell whether this was a nuclear blast, Gardine was definitive: “For a trained seismologist, within seconds of looking at the data, it’s very obvious, it’s a different signal from an earthquake.”

Dr. Kenneth Macpherson, a Watchstander and Physical Scientist with the National Tsunamic Warning Center in Palmer, echoed that sentiment.

Macpherson says it was “blindingly obvious” that this seismic event was a nuclear test and not a normal earthquake.

“The first thing you notice is the location, it’s become very well known to us,” said Macpherson.

The area is not known to be seismically active and North Korea has conducted previous nuclear tests in the same area, says Macpherson.

There were other clues for Alaskan scientists.

“The origin time is right on the half hour, 00:30 and almost 00. You could get an earthquake right on the half hour but it’s just another clue that someone is looking at a timer when they pushed the button,” said Macpherson.

Both Macpherson and Gardine say the data indicates this was a shallow test and the waveforms were entirely different to those of a natural earthquake.

Macpherson described them as “impulsive” with a lot of “compressed energy.”

The data that was collected across Alaska by the Alaska Earthquake Center in Fairbanks and the National Tsunami Warning Center in Palmer was then sent to the United State Geological Survey.

Macpherson says due to the risk of Tsunamis and the need for a quick response, the NTWC can detect seismic activity anywhere in the world, analyze it, evaluate it and determine whether it will cause a tsunami within four minutes of the event.

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