- The Washington Times - Thursday, August 22, 2019

The United States has improved its ability to differentiate earthquakes from underground explosions, according to leading seismologists who have just concluded nine years of experiments at the Nevada National Security Site.

Amid increasing concerns over nuclear threats around the world, the work is being seen as a boost to U.S. efforts to monitor underground weapon explosions and keep countries like Russia in compliance with nuclear treaty commitments.

Scientists are calling the National Nuclear Security Administration-sponsored project “the finest explosion dataset” of this type in the world. It also has been noted for its timeliness, given that North Korean underground thermonuclear tests initially have been mistaken for earthquakes.

“Our goal was to get a better understanding of the difference between a natural earthquake and an explosion of some sort, whether it be a nuclear explosion, or not,” Sandia National Laboratories seismologist Rob Abbott told The Washington Times.

Nuclear devices have been tested underground for decades to prevent releasing radioactive material into the atmosphere and ensure a degree of secrecy. Early in the Cold War-era, scientists realized that earthquake-detecting seismology sensors also could detect underground blasts.

That discovery triggered the creation of the first standardized seismographic network in the 1960s, largely as a way to obtain reliable data for monitoring underground nuclear explosions, according to British scientists Neil Wilkins and Stephen Hicks.

Currently, more than 150 seismic stations dotted around the globe monitor whether countries are in compliance with the 1996 Comprehensive Nuclear-Test-Ban Treaty.

According to Mr. Abbott, the U.S. launched the new experiments because America had stopped nuclear testing in the early 1990s and required new tools to “understand more about the physics of explosions.”

Additionally, “much of our old data was from just a few locations on earth, including U.S. test sites in Nevada or ones from the former Soviet Union and China,” he said.

The Source Physics Experiments (SPEs) were conducted by seismologists from the National Nuclear Security Administration, the Nevada National Security Site, the Los Alamos National Laboratory, the Lawrence Livermore National Laboratory in California, the Sandia National Laboratories in New Mexico and the University of Nevada-Reno. (The federally funded Sandia labs have roots stretching back to World War II and the Manhattan Project’s development of the first atomic bombs.)

The SPEs involved underground, high-explosive detonations in holes — sometimes deeper than 1,200 feet — in the Nevada deserts. Some explosive canisters contained more that 10 metric tons of TNT equivalent chemicals, with blasts analyzed by as many as 1,500 sensors, high-speed video, geological mapping, drone-mounted photography and other instruments.

The final underground explosion in the series took place June 22.

Brent K. Park of the National Nuclear Security Administration said the SPE trials “improve our ability to monitor potential explosions across the globe.”

Zack Cashion, a chief engineer with Sandia, explained via email that test days involving massive explosions could be tense.

“You’re sitting there watching your screen and it’s ‘Three, two, one, fire,’ and then you might not feel anything,” Mr. Cashion wrote. “You’re waiting there for, it might be four seconds, but it feels like an eternity, and then you go look at the data and wipe your brow that the event occurred as planned and that it was indeed recorded.”

CORRECTION: An earlier version of this story reported that some experiments to boost U.S. efforts to monitor underground weapon explosions occurred in New Mexico. While some analysis was conducted in New Mexico in addition to other locations, all explosions occurred at the Nevada National Security Site.

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