A modest earthquake left Southern California with the jitters Monday but no serious damage as the temblor caused swaying and rolling from the desert to the coast, sending children scrambling under their desks and office workers running for the door.
The 9:55 a.m. quake had an estimated magnitude of 4.7, said Nick Scheckel, seismic analyst at the California Institute of Technology's seismological laboratory in Pasadena.
The epicenter was about a dozen miles from the Riverside County desert community of Anza, about 100 miles southeast of Los Angeles, and it was felt strongly at the BNP Paribas Open tennis tournament happening in nearby Indian Wells.
The temblor, which occurred at a depth of eight miles, caused a swaying or rolling motion in Los Angeles and San Diego as well as in Orange and San Bernardino counties. It was sandwiched between several foreshocks and aftershocks.
"It kind of shook and then I thought, 'God, is that an earthquake?'" said Susie Bride, a cashier at Cahuilla Mountain Market and Cafe in Anza. "It kind of shook and then it rolled a little bit and then it shook again."
There was no damage at the store, and authorities said there were no reports of damage or injuries in the region. Quakes of that magnitude are unlikely to do much harm to modern buildings, said Lucy Jones, a seismologist with the U.S. Geological Survey in Pasadena.
At the BNP Paribas Open, tennis star Rafael Nadal felt the shaking while he was on the massage table preparing for his third-round match against Leonardo Mayer of Argentina and said he was "very scared."
It was the Spaniard's first earthquake experience and he said his legs were wobbling from it.
The temblor was a strike-slip earthquake on the San Jacinto Fault, the most active fault in Southern California, Jones said.
In the past two decades, there have been five quakes of magnitude 4.7 or greater on the fault, she said, and in the 20th century there were eight quakes of magnitude 6 and above.
The quake's preliminary magnitude estimate of 5.1 was changed after a review by seismologists, which is not uncommon. The computer also erroneously took readings from the main shock and increased the magnitudes of foreshocks and an aftershock, causing confusion.
Rachelle Siefken was at home in the Riverside County town of Aguanga with her 4-year-old daughter and 16-month-old son when the shaking started. It was the first earthquake for both children and her son in particular was scared, she said.
"I grabbed him up in my arms and I stood in the doorway with him," said Siefken, who teaches English online for the California Virtual Academy.
Contributing to this report were Associated Press writers Tami Abdollah, Sue Manning, Greg Risling, Justin Pritchard, Robert Jablon and John Antczak in Los Angeles; Gillian Flaccus in Orange County; and Beth Harris in Indian Wells.