Quake shakes Southern Calif.

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,' seismologist Kate Hutton said 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, Department of Water and Power spokeswoman Kim Hughes said.

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.'