'Major Seismic Activity': 5.4 Magnitude Quake Jolts Southern Calif.

July 29, 2008 — -- A large earthquake struck the Los Angeles area shortly before noon today, shaking buildings and leading to some evacuations, but no immediate damage or injuries were reported.

The 5.4 magnitude earthquake was felt throughout Southern California and as far away as Las Vegas.

The earthquake struck at 11:42 a.m. local time and lasted for some 30 seconds. Residents reported that it was the strongest quake they had felt in the area since the 1994 temblor in Los Angeles' San Fernando Valley, which measured a magnitude of 6.7, almost ten times stronger than today's quake. That quake led to 72 deaths, 9,000 injuries and $25 billion in damages.

"I was at my house when I felt everything shaking," said Sharmalee Samel of Hemet, Calif., about 60 miles from L.A. "Pictures started falling down off the walls and I grabbed my infant and went under the table. There was stuff falling off the shelves."

According to the U.S. Geological Survey, the epicenter of today's earthquake was 29 miles east, southeast of Los Angeles and 7.6 miles underground.

There is a 5 percent chance that today's earthquake was a foreshock to a much larger quake that could occur in the next three days, according to the USGS.

"There is a one in 20 chance that something bigger than a 5.4 will occur in the next three days. There is a possibility this was just a foreshock," Susan Hough, the scientist in charge of the USGS, told ABC News.

Los Angeles police and fire departments reported no immediate damage or injuries. Hospitals closer to the epicenter in Chino Hills, Calif., also reported no injuries.

The short duration of the earthquake led to some, but not many, building evaluations. Schools were evacuated and a water main broke in downtown L.A.

"It got worse and worse and worse, and I walked to the entryway door in the front of my house and I realized it wasn't going to stop," said Nancy Bumstead, a mother from Ontario, Calif., who was at home during the quake. "And my garage door was open and all kinds of stuff fell in the garage. Everything that was in there started crashing down -- it was crazy."

Wendy Greuel, the acting mayor of Los Angeles, said there was only "minor structural damage" to buildings downtown.

The city's infrastructure was in full working condition with "no reports of damage" to the water systems or power grid, she said.

Cell phone service was temporarily suspended, but all networks are now fully functional. All bus and train lines are operating normally, but the underground metro is operating at reduced speed. The metro, Greuel said, automatically shuts down during a 5.3 or stronger quake.

Local airports are also operating normally. A radar tower was damaged at Los Angeles International Airport, but flights were unaffected. Some minor damage was reported to runways at John Wayne and Ontario airports.

Greuel told Angelinos to be prepared for a possible larger earthquake in the next one to three days.

"In the event of large aftershock, we will provide shelters at city facilities," she said. "All of us who live in Southern California live with possibility of an earthquake every day. Now is the time for parents to speak with children about safety. Now is the time for families to have a plan of action in case of an emergency."

Gov. Arnold Schwarzenegger said state officials would inspect levees and bridges in Southern California for damage.

He said he was briefed in the immediate aftermath of the quake and was being regularly briefed by emergency officials.

"We're fanatics about emergencies and being ready because, after Katrina, what has happened made us really re-evaluate everything," he said.

As many as 26 aftershocks were recorded by the USGS, but only a few were strong enough to be felt.

Many buildings in L.A. have been retrofitted and designed to sway during a quake.

"There are parts of the world where a 5.4 can be a serious disaster," said Kate Hutton, a staff seismologist at Caltech, who attributed the avoidance of damage and injuries to California's building regulations.