The epicenter of the quake that occurred at 2:41 a.m. Tuesday was on the Hayward Fault, at a spot just north of the intersection of two roads, Niles Canyon Road and Mission Boulevard.

The Hayward Fault stretches from San Pablo Bay in the north to Fremont in the south, passing through Berkeley, Oakland, Haward and Fremont.

"While a 2008 report put the probability of a 6.7-magnitude or larger earthquake on the Hayward-Rodgers Creek Fault system over the next 30 years at 31 percent, Brocher said the reality is a major quake is expected on the fault 'any day now.'" (Source: CBS)