China has detained a 54‑year‑old US seismologist who monitored North Korea’s nuclear tests for nearly two years on espionage charges, his family says.
Chen Youlin was arrested in November 2024 during a visit to Beijing, according to the advocacy group Global Reach. The family went public only after seeing no sign of his release.
His wife Rong Yufang, also a seismologist, said Chen worked closely with Chinese colleagues, and the allegations are “both wrong and inconsistent with the public and collaborative nature of the work that he has done.”
Chen’s research has focused on seismic signatures from North Korean nuclear tests – a subject that China, a close friend of North Korea, has heavily sanctioned for its nuclear programme.
The US intelligence community suggests China is developing a new arsenal and may have conducted secret tests, which Beijing denies. Whether Chen’s work intersected with China’s own nuclear programme is unclear.
At a press briefing, China’s foreign ministry said its “judicial authorities handle cases in accordance with the law.” The spokesperson, Lin Jian, said “there is no such thing as wrongful detention.” In China, espionage convictions can lead to life imprisonment or the death penalty.
Chen is the only US citizen currently designated as “wrongfully detained.”
Rong told Global Reach she has not spoken with her husband for over 600 days and is concerned for his health. After 13 months of detention, Chen was denied a lawyer and was interrogated more than 100 times about his work.
Born in China, Chen became a US citizen in 2011 and lives in Boston. He specialises in using seismological data to identify nuclear tests and has worked on several US‑funded projects. Rong said his work with Chinese colleagues was always transparent.
Relating to his research, Chen published a 2020 study using seismic data across Asia, including China, to improve nuclear‑test monitoring and yield estimation.
Global Reach notes suspicions that the arrest was provoked by China’s possible violations of the Comprehensive Nuclear Test Ban Treaty, fears that the US could learn about Chinese countermeasures.
The treaty bans all nuclear explosion tests, yet several states, including the US and China, have yet to ratify it. Both have voluntary moratoria on explosive testing.
In June 2020, the Trump administration accused China of conducting a covert underground test at the Lop Nur facility. China dismissed the claim as politically motivated.
The Foley Foundation highlighted Chen’s diabetes, high blood pressure and cholesterol, urging reliable medical care while he remains incarcerated.
US Senator Edward Markey said the detention undermines China‑US partnership and could deter scholars from engaging in China, hoping increased pressure will prompt release.
The arrest follows China’s earlier detention of US scholar Min Zin, director at a Myanmar‑focused think‑tank, whom Beijing accuses of spying.
