From the London Mail [caution, tabloid]:

California has been rattled by multiple earthquake swarms over the past four days, with the latest hitting on Tuesday. The US Geological Survey (USGS) reported a 3.1-magnitude quake at 5.53am PT (8.53am ET) near San Roman, the epicenter of the recent seismic activity. This tremor followed a dozen smaller quakes ranging from 1.1 to 1.6 magnitude.<[scroll for more:]

The seismic activity has sparked concerns among locals, fearing the uptick is foreshadowing a major event, but USGS research geophysicist Annemarie Baltay said she is not unusually concerned that anything bigger will hit San Ramon.