"The first thing we thought was that L.A. went down and we were on the other end of it," Sparkes said as he shopped at a supermarket a few hours after the magnitude 5.4 quake. "It was a hard shake and it lasted about 30 seconds."

The Sparkes had been through stronger Southern California temblors, the 1994 Northridge and the 1987 Whittier Narrows quakes.

"This felt double that," said Debbie Sparkes. The centers of those quakes were much farther from Sparkes' home, though.

Around 30 miles (48 km) east of Los Angeles and home to 80,000 people, Chino Hills is a pleasant suburb with new large homes built among the big rolling hills.

The town returned to normality just a few hours after the temblor and filled up with people shopping and eating out. Only the presence of police, emergency teams and reporters indicated something big had happened.

The Wal-Mart store where some bottles fell off the shelves was back open for business in a few hours, after inspectors made sure nothing would fall and hurt customers.

Some who were too young to remember previous quakes were shocked by the violence of the jolt.

"It woke me up. I almost had a heart attack," said Brittany Williams, 19, who was sleeping in her Chino Hills house and could hear objects falling out of the closets.

Brittany's mother, Melissa Williams, 46, was in a furniture store in nearby Ontario and thought a bomb had exploded.

"It was a big warehouse and police were shopping in there. They said, 'Everybody get out,'" she said.

"It was long -- 30-40 seconds. It didn't stop. Everything was moving fast. I could see the floor rolling."

(Writing by Mary Milliken; Editing by Peter Henderson)