President Trump has stirred up debate by claiming Russia and China are secretly conducting nuclear weapon tests. This assertion, particularly his suggestion that these tests might be hidden underground, has ignited confusion among experts who monitor nuclear explosions. They firmly maintain that major nuclear powers haven’t conducted explosive nuclear tests since the 1990s when the Comprehensive Nuclear-Test-Ban Treaty came into effect, establishing a global norm against such detonations.
Trump made his claim in an October 31 interview with CBS’s 60 Minutes. “Russia’s testing, and China’s testing, but they don’t talk about it,” he stated, adding that these tests often occur “way underground where people don’t know exactly what’s happening.”
However, scientists possess sophisticated tools to precisely track nuclear explosions. The last nation confirmed to have conducted such tests was North Korea, from 2006 to 2017, at its Punggye-ri testing site. These underground blasts were quickly identified through the tremors they produced and the release of distinctive radioactive isotopes created during the detonations.
To understand how confidently we can monitor nuclear activity around the globe, Science News spoke with Thorne Lay, a seismologist from the University of California, Santa Cruz, who has dedicated decades to research in this field.
Detecting Detonations: An International Network’s Watchful Eye
Lay explained that for several decades, technology has existed to monitor explosions—whether air bursts, underground detonations, or underwater blasts—anywhere on Earth. This monitoring relies primarily on detecting the seismic waves, sound waves traveling through water and air, generated by an explosion.
“For the last 20 years,” Lay noted, “there’s been an international monitoring system that the U.S. is part of.” This system operates a vast network of:
- Seismic Stations: Tracking ground vibrations
- Hydroacoustic Stations: Listening for underwater sound waves
- Infrasound Stations: Detecting atmospheric sound waves
- Radiochemical Testers: Collecting air samples to identify released isotopes.
This global network, comprising hundreds of stations, supplements existing seismic networks already monitoring earthquake activity worldwide.
The Threshold of Detection: Size Matters
Lay emphasized that the minimum detectable explosion size depends on its location relative to these monitoring stations. “A rule of thumb is that we can monitor everywhere in the world down to about magnitude 4,” he stated. This corresponds to a kiloton explosion (one-fifteenth the yield of the Hiroshima bomb).
However, in areas with historical nuclear testing sites, precise calibrations allow detection of significantly smaller explosions—far below kiloton levels.
The Difficulty of Concealment: Limited Options for Masking
Lay addressed Trump’s suggestion that underground tests could be effectively hidden. While detonating a weapon within a vast underground cavity might marginally reduce the sound signal, it’s unlikely to completely mask the event. This strategy would only work at nearby monitoring stations and is inefficient compared to the sensitivity of modern detection systems.
Distinguishing Nuclear from Other Explosions
Lay explained that distinguishing a nuclear explosion from other types relies on several key factors:
- Magnitude: Explosions exceeding magnitude 6 are exceptionally difficult to achieve through conventional chemical means.
- Isotope Analysis: The release of specific radioactive isotopes, unique to nuclear fission, is a definitive indicator. Underground tests often create surface cracks that allow escaping gases carrying these telltale isotopes to be detected.
Beyond Explosive Tests: A Nuance in Terminology
Lay’s insights highlight the complexity surrounding Trump’s claims, which might blur the distinction between explosive nuclear tests and other types of nuclear testing. These can include experiments on non-nuclear components like propulsion systems or electronics, often conducted in controlled environments without explosive detonations.
This ambiguity underscores the need for precise language when discussing nuclear weapons activities. While international monitoring systems remain remarkably effective at detecting explosive nuclear tests, a nuanced understanding of different types of testing is essential to accurately interpret global nuclear activity.
