U.S. hardens allegation that China conducted secret nuclear test

Wall Street Journal: The U.S. presented new seismic data Tuesday to buttress its recent allegation that China has secretly carried out low-yield nuclear tests, challenging Beijing’s insistence that it has scrupulously observed an international accord banning all nuclear detonations. 

A senior State Department official said that a seismic monitoring station in Kazakhstan had detected a 2.75 magnitude event on June 22, 2020. The U.S. has accused China of conducting a clandestine low-yield nuclear test at that time…