New seismic data challenges Beijing’s nuclear test ban claims
A senior U.S. arms-control official says seismic data from June 22, 2020, point to a suspected low-yield nuclear test at China’s Lop Nur test site. Speaking at the Hudson Institute, Assistant Secretary of State Christopher Yeaw pointed to data from a monitoring station in Kazakhstan that detected a magnitude 2.75 event roughly 450 miles from the test site.
He argued the seismic signature was not consistent with an earthquake or mining blasts and was more consistent with an explosion. Yeaw alleged China used “decoupling” — detonating in a large underground cavity — to reduce the seismic signal and make the event harder to detect.
Nuclear test bans
The allegation comes as the global test-ban regime and U.S.-Russia arms limits are fraying. The 1996 Comprehensive Nuclear Test Ban Treaty bans nuclear explosive tests but has never entered into legal force because key countries, including the United States and China, have signed but not ratified it. Reuters and NPR note that Washington currently maintains its arsenal through sub-critical experiments and advanced computer modeling rather than full-scale detonations.
Meanwhile, the New START treaty, which limits the number of deployed strategic warheads for the U.S. and Russia, has expired. Pentagon estimates cited by Newsweek indicate that Beijing is rapidly expanding its nuclear stockpile, which has grown from a few hundred warheads to a projected 1,000 by 2030. Chinese officials counter that their forces remain far smaller than those of Washington and Moscow and say the two larger powers should lead on disarmament.
What US, Chinese and monitoring officials say
Yeaw stated that the 2020 event was a “yield-producing” test, meaning it triggered a nuclear chain reaction, and that the U.S. is aware of such testing activities in China. While he wouldn’t estimate the blast’s specific size due to alleged concealment efforts, he warned that if adversaries can conduct undetectable low-yield tests while the U.S. adheres to a “zero-yield” standard, Washington would face an “intolerable disadvantage.”
The Comprehensive Nuclear-Test-Ban Treaty Organization confirmed that its sensors picked up two minor tremors, separated by just 12 seconds, on that date. However, Executive Secretary Robert Floyd cautioned that the signals were too faint to definitively identify a nuclear source without more data. Ben Dando, a seismologist at the Norwegian monitoring group NORSAR, told NPR that a weak signal from a single station makes it impossible to “confirm or deny” whether a nuclear test occurred.
Chinese officials have rejected the allegation as “completely groundless,” accusing the United States of inventing excuses to justify resuming its own testing and pursuing “its own resumption of nuclear tests.”
What independent analysts see at Lop Nur
Satellite analysis highlights activity at China’s Lop Nur test site but does not resolve what happened in 2020. A Center for Strategic and International Studies analyzed satellite imagery of a specific tunnel at the site. The review found no visible proof to confirm or deny the allegations, though analysts noted that the site’s vast size makes it difficult to rule out underground activity based on images alone.
Daryl Kimball of the Arms Control Association told The Wall Street Journal that a U.S. return to testing in response to these claims would be “technically unnecessary” and could provoke a cascade of new testing by other nuclear powers.
What could come next on arms control and testing
Yeaw said he expects to discuss nuclear issues with Chinese and Russian counterparts at a United Nations forum in Geneva next week. NPR and Newsweek report that U.S. officials are weighing options that include adding more nuclear warheads to existing missiles, bombers and submarines, even as they hope to negotiate new arms-control arrangements that include China and Russia.
Fox News reports that in October 2025, President Donald Trump said the United States is considering resuming nuclear tests on an “equal basis” with other countries.
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Ella Rae Greene, Editor In Chief
