Becoming Independent's sprawling southwest Santa Rosa site is filled with tables where developmentally disabled clients work, make art, learn computers and eat.

On Thursday staff and clients scrambled under tables Thursday as part of a statewide earthquake drill dubbed The Great California ShakeOut.

Because of an earlier drill in August, Gloria P. Huerta Jr. said she knew right away what to do and crawled under the table where she'd been drawing. She later demonstrated how she covered her head and pink ball cap with her hands.

Paula Scarborough was prevented by her wheelchair from dropping to the floor and crawling under anything but she said: "I just knew what to do." And that was to cover her head and neck with her arms and hands as she'd been told.

That's the point, organizers said.

An earthquake comes with no warning and little opportunity to seek safety, so those living in earthquake country need to think ahead and practice what to do so it comes automatically.

With experts predicting a 63 percent chance that the Bay Area will have a quake measuring 6.7 or greater by 2038, residents need to learn how to reduce injuries and figure out how to rely on themselves for at least several days afterward.

More than a million Bay Area residents — including nearly 50,000 in Sonoma County — were registered to take part in Thursday's 10:21 a.m. drill, which was expected to have statewide participation of more than 7.8 million people.

At Becoming Independent, the staff has to consider the safety of 500 people, most of them clients and some of them working or traveling outside the facility, said Cami Weaver, chief executive officer of the agency, which provides work opportunities, training, recreation and other services for the developmentally disabled.

The agency recently brought earthquake drills into its regular rotation of emergency drills, and those off-site at 10:21 a.m. Thursday were told to look around wherever they were — at Mary's Pizza, FoodMaxx, or on the road between two points — and to talk about what they would do if an earthquake were to strike, said Lois Shelton, director of administration.

"We really want to be self-sufficient," Weaver said. "We want to be resourceful."

The need for self-reliance is one reason a larger drill is planned next week at Sonoma Valley's 55-and-up Creekside Village, said resident Charlene Rundstrom.

"We're very cognizant of the fact that we have a vulnerable population here," said Rundstrom, who dropped to her hands and knees and crawled under her kitchen table when the radio announced 10:21 a.m.

The ShakeOut started in 2008 as The Great Southern California ShakeOut and last year expanded to include the entire state and a record 6.9 million people, organizers said.

The ShakeOut comes on the 142nd anniversary of a quake estimated at 6.8 that struck the Hayward Fault underlying major portions of the Bay Area. Experts anticipate a similarly large quake in the next several decades.

More information is available at www.shakeout.org.