The epicentre of the quake, which struck at about 10am local time (4pm UK time), was 6.2 miles (10km) below the surface.
The National Oceanic and Atmospheric Administration (NOAA) has not yet issued a tsunami warning for the West Coast of the US.
The news comes amid heightened fears of California being rocked by a manitude 7.0 earthquake or greater, known as the ‘Big One’.
California sits on top of the potentially catastrophic San Andreas Fault, one of the most seismically active regions in the world.
The Southern California Earthquake Center last year warned small earthquakes along the faultline could trigger a larger one in the future.
Professor Thomas Jordan said: “Any time there is significant seismic activity in the vicinity of the San Andreas Fault, we seismologists get nervous.
“Because we recognise that the probability of having a large earthquake goes up.”
San Francisco, where residents live with the constant threat of tremors, is no stranger to earthquakes.
A devastating 6.9 magnitude quake killed 63 people, injured 3,757 and damaged countless buildings in 1989.
And 3,000 were killed by a 7.8 magnitude quake in 1906 which levelled the city with its powerful tremors.
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