Commuting is the focus of today's Great California ShakeOut, which is being billed as the "largest earthquake safety drill in U.S. history."

Across the state in schools, offices, hospitals and -- for the first time -- Union Station in downtown Los Angeles, people will be asked to drop, cover and hold on during the annual drill. Metro trains will also slow down at 10:18 a.m. as if a real earthquake occurred.

More than 9.3 million Californians are expected to take part.

"This is the first time we're focusing on commuters for a ShakeOut event," said John Bwarie, a spokesman for the U.S. Geological Survey. "There’s about 250,000 just in Southern California, based on numbers from 2008, that commute across the San Andreas fault."

In Union Station, where more than 75,000 people pass through each day, a recording is to be played over loudspeakers, asking commuters and passersby to drop to the ground, take cover underneath something sturdy and hold on until the shaking stops.

Register for the Great Shakeout here.

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