A magnitude 4.2 earthquake shook the San Francisco area Friday at 4:42 a.m. PT (7:42 a.m. ET), the U.S. Geological Survey reported.

The quake left about 2,000 customers without power, said David Eisenhower, a spokesman for Pacific Gas and Light.

Under the USGS classification, a magnitude 4.2 earthquake is considered "light," which it says usually causes minimal damage. Read full article »