The epicenter was near Isleton, about 20 miles northeast of Antioch.
Many people in the Bay Area felt the shaking, mostly in the East Bay.
RELATED: 4.2 magnitude earthquake strikes in Sacramento County, USGS says
But the bigger question is, did you get the alert?
Many Bay Area residents got a loud notification when it happened. Not only that, the alert listed the quake at 5.7. Why?
Dr. Angie Lux with the Earthquake Early Warning Project at the Berkeley Seismology Lab joined ABC7's "Getting Answers" to talk about the alert system and how well it worked Wednesday.
We asked Lux all about "ShakeAlert" and the "My Shake App" and what Berkeley Seismology Lab's relationship is with the system, as well as how it is decided who receives these alerts.