Detecting Underground Weapon Tests with 99% Accuracy: The Elimination of Nuclear Secrecy?

There has been a significant scientific advancement that enables scientists to detect underground nuclear tests with 99% accuracy, enhancing global security monitoring capacities. This efficient method differentiates nuclear explosions from natural seismic events, utilizing existing seismic data and aiding the enforcement of international surveillance versus secret nuclear testing.

With the new breakthrough in detection methods, underground nuclear tests performed in secret could become outdated.

Earth scientists and statisticians claim that they can now ascertain with 99 percent accuracy whether an explosion has occurred. This has improved from 82 percent and is reliant on a dataset of familiar tests in the United States as mentioned in the latest study published in the Geophysical Journal International. It was previously challenging to distinguish between nuclear explosions and other seismic sources like natural earthquakes or man-made noise above the ground.

"An explosion gets triggered, and this energy radiates out, which can be gauged on seismometers," said lead author Dr. Mark Hoggard of The Australian National University (ANU). "The scientific problem then becomes how we distinguish between that and a naturally-occurring earthquake."

Seven years ago, this issue presented itself when several existing methods used to recognize underground nuclear explosions failed to ascertain that North Korea had performed such a test.

The North Korean state, known for its secrecy, later confirmed they had successfully tested a weapon with a force varying between 100-370 kilotons. As a comparison, a 100-kiloton bomb is six times more powerful than the one the US dropped on Hiroshima in 1945.

In the 21st century, North Korea is the only known country to have performed an underground nuclear test. However, satellite imagery revealed last year that Russia, the US, and China have all constructed new facilities at their nuclear test sites in recent years.

Even though there are no suggestions that the three superpowers are planning to resume such experiments, the war in Ukraine has disrupted the global security landscape.

"By employing revised mathematics and more advanced statistical treatment, we've improved the classification success rate from 82 percent to 99 percent for a series of 140 known explosions in the US," informed Dr. Hoggard. "The US has mostly carried out nuclear testing in Nevada - in the desert - and all these tests have extensive seismic records, so it provides an extremely useful dataset. Our new method also successfully identifies all six tests performed in North Korea between 2006 to 2017, "he added.

Dr. Hoggard mentioned that there may still be situations of underground nuclear tests being conducted secretly in several parts of the world. The sheer volume of earthquakes makes it challenging to inspect each event to ascertain if it is suspicious or not.

He emphasized the importance of effective methods, like the one his team developed. "We don’t need any additional equipment - no need for satellites or such, we're just employing standard seismic data."

Dr. Hoggard mentioned that the model is "quite fast," making it "more or less appropriate for real-time monitoring."

A team comprising Earth scientists and statisticians carried out the research at ANU and the Los Alamos government research lab in the US.

They referred to the new technique as "a method to rapidly evaluate the probability of an event being an explosion."

The experts constructed the mathematical model by analyzing the physical differences in the pattern of rock deformation at the source of nuclear explosions and earthquakes. This enables them to determine whether a recorded noise is more likely to belong to a seismic event.

Following the Cuban Missile Crisis and Partial Nuclear Test Ban Treaty in the 1960s, international efforts were diverted towards monitoring substantial seismic waves. This agreement limited the testing of nuclear weapons to underground only, after years of damaging experiments on the surface and/or underwater that polluted many areas and led to catastrophic levels of radioactive fallout. But this new monitoring brought new challenges, primarily differentiating between nuclear explosions and other seismic sources.

It has taken more than six decades, but the scientists behind the new research believe their innovative method could now make this a lot easier for groups such as the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), which is tasked with international surveillance of nuclear testing.

Dr Hoggard said his team’s mathematical model would be “another tool in CTBTO’s armory for detecting any potential underground tests that are conducted in secret.”

He added: “A ban on all future tests is unlikely given that several major nations remain unwilling to ratify the Comprehensive Nuclear-Test-Ban Treaty. Well-supported monitoring programs are therefore critical for ensuring that all governments are held accountable for the environmental and societal impacts of nuclear weapons testing.”