USGS put this note on their Earthquake website.

"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 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."

https://earthquake.usgs.gov/earthquakes/map/