Robert DeGroot, operations team lead for the USGS-managed ShakeAlert Earthquake Early Warning System, told SFGATE that at least four sensors across Nevada detected motion, leading to an automated warning sent out via MyShake Alert to a large portion of California.

“On December 4, 2025, the ShakeAlert EEW system released an incorrect alert for a magnitude 5.9 earthquake near Reno and Carson City, Nevada,” the statement read. “The event did not occur, and has been deleted from USGS websites and data feeds. The USGS is working to understand the cause of the false alert.”