A mysterious seismic signal in 2020 is back in the spotlight — and Washington says it may point to a hidden Chinese nuclear test.
A senior U.S. official has disclosed new details about what Washington believes was a covert Chinese underground nuclear test in June 2020, an allegation Beijing firmly denies.
Speaking at the Hudson Institute in Washington, Assistant Secretary of State Christopher Yeaw said seismic data from a monitoring station in Kazakhstan detected what he described as a magnitude 2.75 “explosion” on June 22, 2020, near China’s Lop Nor test site in western China.
Yeaw said the signal, recorded roughly 450 miles away, was inconsistent with mining activity or natural earthquakes. Based on his review of additional data, he argued that the event matched what would be expected from a nuclear explosive test, possibly conducted using a method known as “decoupling” to muffle seismic signatures.
China’s last officially acknowledged nuclear test took place in 1996. Beijing has signed, but not ratified, the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which prohibits all nuclear test explosions. The United States has also signed but not ratified the treaty.
The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), which operates a global monitoring network, said the data were insufficient to confirm that a nuclear test had occurred. Executive Secretary Robert Floyd noted that the seismic station in question recorded two small events spaced seconds apart but said they were below the threshold typically associated with nuclear explosions detectable with confidence.
China’s embassy in Washington rejected the U.S. accusation as “entirely unfounded,” calling it political manipulation aimed at justifying a possible resumption of American nuclear testing. Beijing urged Washington to reaffirm commitments by the five recognized nuclear-weapon states to refrain from testing and to support global nonproliferation efforts.
The renewed allegation comes amid heightened tensions over nuclear arms control. The New START treaty between the United States and Russia expired in February, raising fears of a new arms race. U.S. President Donald Trump has pressed China to join trilateral arms negotiations with Washington and Moscow, but Beijing has resisted, arguing that its arsenal remains far smaller than those of the two superpowers.
According to the Pentagon, China now possesses more than 600 operational nuclear warheads and could surpass 1,000 by 2030 — a buildup that continues to reshape the global nuclear balance.
