US Discloses Additional Data on Alleged 2020 Nuclear Event in China

A senior United States official has presented new information regarding an alleged underground nuclear test conducted by China in June 2020, reviving debate over compliance with global test ban commitments and raising fresh questions about seismic monitoring data.

Assistant Secretary of State Christopher Yeaw stated at a policy forum in Washington that a remote seismic monitoring station in Kazakhstan detected what he described as an explosion measuring magnitude 2.75 on June 22, 2020. According to Yeaw, the event was located roughly 720 kilometers from the monitoring station and traced back to the Lop Nor nuclear test site in western China.

Yeaw said the characteristics of the seismic signal were not consistent with natural earthquakes or routine mining activity. Drawing on additional data analysis, he argued that the waveform patterns indicated a singular explosive event. He described the data as aligning with what would be expected from a nuclear explosive test rather than a conventional industrial blast.

The allegation has been strongly rejected by Beijing. A spokesperson for the Chinese embassy in Washington called the claim unfounded and characterized it as political manipulation. Chinese officials have repeatedly stated that the country adheres to its commitments under the Comprehensive Nuclear Test Ban Treaty framework and does not conduct nuclear test explosions.

The Comprehensive Nuclear Test Ban Treaty Organization, which operates a global network of monitoring stations designed to detect nuclear detonations, said available data was insufficient to confirm with confidence that the 2020 seismic event was a nuclear blast. The organization relies on a combination of seismic, hydroacoustic, infrasound and radionuclide detection systems to assess suspicious events.

The renewed discussion comes at a time of broader strategic competition between Washington and Beijing. Nuclear transparency and arms control compliance have become increasingly sensitive topics as both countries modernize aspects of their military capabilities. Although the Comprehensive Nuclear Test Ban Treaty has not formally entered into force, many states observe voluntary moratoriums on nuclear testing.

Seismic events near former test sites can draw scrutiny due to the technical challenge of distinguishing between natural geological activity and underground explosions. Analysts typically examine signal depth, waveform characteristics and corroborating sensor data to determine the likely cause.

The United States has previously raised concerns about possible low yield nuclear activities in various countries, arguing that maintaining robust monitoring standards is essential for global security. China has maintained that it supports nuclear non proliferation efforts and opposes the resumption of nuclear testing by any state.

As discussions over arms control frameworks continue, allegations related to past test activity underscore the importance of verification mechanisms and transparent communication between major nuclear powers. The issue is likely to remain part of ongoing diplomatic exchanges as both sides navigate a complex security relationship.