The quake happened around 7:46 p.m. and was centered 3 miles northwest of Dublin. It had a depth of 7 miles.
It was felt in parts of the Bay Area, including San Francisco.
Meteorologist Sandhya Patel says the epicenter of the quake was likely near the Calaveras Fault.
The quake was downgraded from a 4.2 then revised to a 4.0.
So far, there are no reports of injuries or damage.
BART says it finished inspecting its tracks for damage and for passengers to expect residual delays of up to 20 minutes systemwide.
But if you did not receive a ShakeAlert notification on your phone, there is a reason for that.
ABC7 spoke with Robert-Michael de Groot, Ph.D. Coordinator for Communication, Education, Outreach, and Technical Engagement at ShakeAlert Earthquake Early Warning System.
He said the Shake Alert Activation Warning System was activated, but was not delivered to people's cellphones since the quake was below the 4.5 threshold.
MAP: Significant San Francisco Bay Area fault lines and strong earthquakes
Zoom in on the map below and compare where you live to the significant faults and where strong earthquakes have struck in the Bay Area.
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