Hold on to your feather boas and loose accessories! 

The U.S. Geological Survey says a "mild" earth quake rumbled through the San Francisco area at about 4:45 on Friday morning leaving thousands of customers without electricty and bit rattled.

Under the USGS classification, a 4.2-magnitude earthquake is considered "light," which it says usually causes minimal damage according to CNN.blog.

"We had quite a spike in calls, mostly calls of inquiry, none of any injury, none of any damage that was reported," said Capt. Al Casciato of the San Francisco police. "It was fairly mild."

The quake was centered about two miles northeast of Oakland, at a depth of 3.6 miles, the USGS also said. Oakland is just east of San Fran, across the San Francisco Bay.

The shaking lasted about 50 seconds, said CNN meteorologist Chad Myers.   Police report that the quake set off home and car alarms throughout the area.

According to the USGS, 4.2-magnitude quakes are felt indoors and may break dishes and windows, and overturn unstable objects. Pendulum clocks may also stop working.