Big Ideas Lab Podcast takes on earthquakes and nuclear explosions

What do an earthquake, a mine collapse and a nuclear explosion have in common? Learn the answer to this question and more on a new episode of the Big Ideas Lab Podcast from Lawrence Livermore National Laboratory (LLNL). The episode provides insights into how Lab scientists monitor seismic activities such as earthquakes and nuclear explosions to ensure the safety of people and the world. Listen on Apple or Spotify.

Bill Walter leads a team of LLNL scientists dedicated to seismic and nuclear test monitoring: work that plays a key role in tracking nuclear explosions globally and understanding seismic activity. Scientists at the Lab are constantly monitoring both natural seismic events, like earthquakes, and human-created explosions.

Walter’s work is part of an ongoing legacy that began during this time of scientific and diplomatic cooperation between the U.S. and the Soviet Union. The challenges remain significant: with seismic monitoring at the forefront of keeping the world safe from hidden nuclear detonations. Nuclear tests are still happening today. Countries like North Korea have continued to develop and test nuclear weapons, often in defiance of international law. But how do we detect these tests? The answer lies underground.

“I remember very distinctly, I was taking my youngest daughter to college in September of 2017, and I helped her move in, and I was back in my hotel room, and I was checking my email, and there's a note ... I had one of these emails, which doesn't happen very often, and immediately looked at it compared to past North Korean tests and saw that this is probably a North Korean nuclear test,” he said. “And there was immediately a flurry of Tweets going on about people saying, this looks like a North Korean test. And people were immediately trying to do analysis and things like that. So there is a very active international community that follows this stuff. And it's activated in minutes.”

Seismic monitoring became critical in the 1960s during the Cold War when nuclear tests were forced underground. The Limited Test Ban Treaty banned nuclear tests in the atmosphere, outer space and underwater. This shift meant that detecting underground nuclear detonations became vital for global security, and seismic analysis quickly emerged as the primary tool.

“If an explosion goes off in the ground, it generates seismic waves just like an earthquake does,” Walter said. “And in fact, the waves look a lot like an earthquake. And so the big challenge is when we detect seismic waves, what's the source? What's the cause of them? Is it an earthquake? Is it an explosion? Is it a mine blast? Is it some kind of an accident? There are many things that can generate seismic waves.”

When seismic waves are generated, they travel through the Earth, bouncing off different layers of rock, soil and water. These waves are picked up by sensors all over the world, forming the foundation of global nuclear test monitoring systems. 

"Seismic means an event that generates waves that propagate through the Earth” said Arben Pitarka, an LLNL scientist working with Walter’s group. “And those are seismic waves. They are important because those are the signals that tell us where the source was located, what was the origin, what was its content, what was the magnitude of that event. So all these are characteristic of a seismic event."

This kind of research is paying off. In places like San Francisco, where the risk of a major earthquake looms large, scientists are using seismic data to help create buildings that can better withstand the tremors. And while the science is complex, the goal is simple: to keep people safe.

Seismic research does more than uncover hidden tests; it deciphers the unseen movements of our world, building trust and accountability on a global scale. As technologies advance, so must our efforts to outpace those who seek to obscure their activities, ensuring that our commitment to a safer, more transparent future remains unshaken.

Tune in to the latest episode of the Big Ideas Lab Podcast to dive into the LLNL research that can decipher at nuclear test in North Korea from the latest temblor. Listen on Apple or Spotify and stay tuned for another episode this week!