LOS ANGELES A strong earthquake shook Southern California on Tuesday, causing buildings to sway and triggering some precautionary evacuations. There were no immediate reports of damage or injuries.
The jolt was felt from Los Angeles to San Diego, across the border in Tijuana, Mexico and slightly in Las Vegas.
The 11:42 a.m. quake was initially estimated at 5.8 by the U.S. Geological Survey but was revised downward to 5.4. More than a dozen aftershocks quickly followed, the largest estimated at magnitude-3.8.
The quake was centered 29 miles southeast of downtown Los Angeles near the San Bernardino County city of Chino Hills, and was estimated to be about 8 miles below the earth's surface.
"It will certainly cause cracked plaster and broken windows, but probably not structural damage," said seismologist Kate Hutton at the USGS office in nearby Pasadena.
The magnitude-5.9 Whittier Narrows quake in 1987 was the last big shake in that area. That quake heavily damaged older buildings and houses in communities east of Los Angeles.
"We had forgotten what a big earthquake felt like, at least I did," Hutton said. "It's a drill for the big one that's going to happen someday."
The Governor's Office of Emergency Services had received no damage or injury reports, said spokesman Kelly Huston in Sacramento.
Los Angeles Fire Department spokesman Brian Humphrey said there were no immediate reports of damage or injury in Los Angeles. San Bernardino and San Diego counties also had no immediate reports of damage.
Buildings swayed in downtown Los Angeles for several seconds.
Workers quickly evacuated some office buildings.
"It was dramatic. The whole building moved and it lasted for a while," said Los Angeles County sheriff's spokesman Steve Whitmore, who was in the sheriff's suburban Monterey Park headquarters east of Los Angeles.
As strongly as it was felt, the quake was far less powerful than the magnitude-6.7 Northridge earthquake that badly damaged the region on Jan. 17, 1994. That quake was the last damaging temblor in Southern California. It killed 72 people, injured more than 9,000 and caused $25 billion in damage in the metropolitan area.
No electrical outages were reported in Los Angeles due to the quake, said Department of Water and Power spokeswoman Kim Hughes.
But the state's Office of Emergency Services urged people throughout Southern California to cut back on telephone usage, saying a flood of calls after the quake had jammed up phone lines.
"The big message now is don't use telephones or cell phones in Southern California," agency Spokesman Kelly Huston said. "The systems down there are maxed out, and that creates a really dangerous situation when it comes to people who need to call 911 for an emergency."
In Orange County, about 2000 detectives were attending a conference on gangs at a Marriott hotel in Anaheim when a violent jolt shook the main conference room.
Mike Willever, who was at the hotel, said, "First we heard the ceiling shaking, then the chandelier started to shake, then there was a sudden movement of the floor."
Chris Watkins, from San Diego, said he previously felt several earthquakes, but "that was one of the worst ones."
Delegates and guests at a cluster of hotels near the Disneyland resort spilled into the streets immediately after the quake.
Huston, the governor's OES spokesman, said officials in Sacramento were on a conference call when the earthquake struck, discussing the availability of firefighting equipment with a Southern California emergency management team.
"They felt it. We could actually hear some shaking on the phone. Now we've completely shifted gears we're on earthquakes," Huston said.
Joseph Maddalena, who runs the historical documents and memorabilia dealer Profiles in History, was on the phone in his office in Calabasas, near Malibu, when the earthquake struck. He quickly put down the phone and ran to check on his 14-year-old son who had come to work with him as he prepared for a Thursday auction of 1,100 pieces of Hollywood movie memorabilia.
"Our building shook pretty good," he said after discovering his son and his employees were unharmed and the building was fine.
"The window in my office kind of bowed out but it's all right now. Everything is fine," he said.
Alfredo Escobedo, director of the emergency protection system in Tijuana, Mexico, just south of the border, said his office had no immediate reports of major damage or injuries.
As a precaution, officials evacuated several buildings, including city hall, some older housing projects and a few businesses.
"I was in one of the top floors, sitting at my desk, when I felt my chair move and the walls began to vibrate," city hall receptionist Maria Teresa Abrau said. "I wasn't scared. I just waited calmly until we were evacuated."
The damage created by an earthquake depends greatly on where it hits. A 7.1 quake much stronger than Northridge hit the Mojave Desert in 1999 but caused only a few injuries and no deaths.
California is one of the world's most seismically active regions. More than 300 faults crisscross the state, which sits atop two of Earth's major tectonic plates, the Pacific and North American plates. About 10,000 quakes each year rattle Southern California alone, although most of them are too small to be felt.