• The U.S. alleges a secret Chinese nuclear test occurred in June 2020.
• A seismic station detected an underground explosion consistent with nuclear testing.
• China denies the allegations and disputes the U.S.'s interpretation of the seismic data.
• The Comprehensive Test Ban Treaty Organization stated that the data is insufficient to confirm the claims.
• Decoupling is mentioned as a potential method China could use to obscure the true nature of its testing.

The U.S. government has provided new intelligence on what it alleges was a covert Chinese nuclear test conducted on June 22, 2020. A remote seismic station in Kazakhstan recorded a 2.75 magnitude event that originated approximately 450 miles away from Lop Nur, China's main nuclear testing site. Assistant Secretary of State Christopher Yeaw stated that "there is very little possibility that it is anything other than an explosion," suggesting it aligns with expectations from a nuclear test, yet independent experts remain cautious, indicating the evidence is not conclusive, according to NPR and Reuters.

Yeaw pointed out that the measurements indicated the event could not be attributed to conventional activities such as mining or natural earthquakes. He described the phenomenon as a singular explosion rather than additional seismic activities characteristic of an earthquake, making it “what you would expect with a nuclear explosive test,” highlighting the potential severity of the event, according to Reuters and India Times.

China has categorically rejected these allegations, with its embassy in Washington labeling the claims as "entirely unfounded." A spokesperson articulated concerns that the U.S. is manipulating these allegations to justify its own nuclear testing within an international framework, emphasizing that these accusations may instigate a renewed arms race, according to NPR, Reuters, and India Times.

The Comprehensive Test Ban Treaty Organization has indicated that the data from the PS23 station is inadequate to definitively confirm the explosion's nature, with Executive Secretary Robert Floyd stating that recorded seismic events fell below levels detectable for confirming nuclear tests. "As a result, with this data alone, it is not possible to assess the cause of these events with confidence," Floyd noted, illustrating the uncertainty within the situation, reflecting the shared sentiments of multiple sources, including Reuters and India Times.

Yeaw has also discussed a technique termed decoupling, suggesting that if China were to conduct a nuclear test, it might employ this method by detonating a device in a large underground chamber. This tactic serves to lessen observable seismic activity effectively, as the explosion would generate significantly less transmission of shockwaves. The Pentagon's assessment declares that China's nuclear arsenal has exceeded 600 warheads, with projections estimating an expansion to over 1,000 by 2030, according to NPR and India Times.