US expert on underground nuclear tests held in China for 18 months
US Expert Held in China for Over 18 Months on Espionage Allegations
US expert on underground nuclear tests - An American seismologist who has researched underground nuclear testing has been imprisoned in China for more than 18 months, accused of espionage. His supporters and a US senator claim the detention is unjust. US Senator Edward Markey stated Tuesday that Youlin Chen has been “wrongfully detained” since November 2024.
Chen’s case gained attention during a May meeting between former President Donald Trump and Chinese leader Xi Jinping in Beijing. Trump highlighted the issue, urging for Chen’s release, as reported by Global Reach, a US non-profit assisting Chen’s family. The organization noted Chen is the sole American currently detained in China labeled as “wrongfully detained.”
Background and Research Focus
Youlin Chen, based in Boston with a college-aged son, has dedicated his career to refining methods for detecting and tracking nuclear tests through seismic data. His work includes analyzing North Korea’s underground nuclear activities. Funded by the US State Department and Air Force Research Laboratory, Chen’s studies have contributed to improving yield estimation techniques. A 2020 technical report, co-authored by Chen, used regional seismic records from across Asia—including Chinese stations—to enhance monitoring capabilities.
In 2024, another study he led, supported by the same US agencies, “further confirms his expertise in seismic analysis of nuclear tests,” Global Reach stated. The research aligns with China’s recent nuclear advancements, including an alleged underground test in 2020 that Beijing has yet to confirm.
Family Concerns and Detention Details
“Youlin has never held a US government security clearance, and to suggest he was involved in espionage is both wrong and inconsistent with the public and collaborative nature of his work,” said his wife, Yufang Rong, in a statement provided by Global Reach.
Chen’s wife expressed worry over his health, noting she hadn’t spoken to him in over 600 days. She emphasized his transparent collaboration with Chinese colleagues on scientific projects. “He is doing precisely the kind of people-to-people engagement that the Chinese government says it wants,” she added.
Chen was arrested at the airport after visiting his parents in Beijing, according to Kieran Ramsey, Global Reach’s chief investigative officer. Despite multiple visits by US embassy officials, Chinese authorities have consistently monitored his interactions, limiting his ability to communicate freely. His wife retained a Chinese lawyer, who only saw him after his detention exceeded 13 months.
Government Responses
A State Department spokesperson confirmed that Chen’s case was directly addressed with Chinese officials and called for his immediate release. However, China’s Foreign Ministry denied the claim of wrongful detention, stating judicial processes are conducted in accordance with local law.
Chen was formally charged with espionage on May 1, 2025, but has not yet faced trial. His family’s decision to speak out now follows Trump’s unsuccessful plea for his freedom. The case intensifies diplomatic tensions between the US and China as both nations seek to stabilize their relationship.