Then on Tuesday afternoon, a 4.7-magnitude quake rumbled east of the Salinas Valley near Hollister in San Benito County.
The shaking was enough to raise people's blood pressure all over the Bay Area. But does it forecast something larger?
In January, KQED Science detailed that a series of small quakes does not necessarily mean the Big One is close at hand.
An earthquake of any size could be a foreshock, said Roland Burgmann, a UC Berkeley geologist.
“That does mean that the probabilities are higher, whenever there is an earthquake, of a larger one,” he said. “But, as best we know, there isn’t a particular magnitude range that would make us more or less worried.”
With both quakes, the U.S. Geological Survey estimated a 2% prospect of a similar sized or bigger quake in the area during the next week.
While the chance of a big temblor is higher than usual, it is by no means imminent, Burgmann said.
Pleasant Hill Quake
The epicenter of Monday’s quake was a few miles west of the Concord fault and north of the Calaveras fault, USGS reported.
Small earthquakes are common near Pleasant Hill, an area with complex geology and many small, unmapped faults.