July 29 (Bloomberg) -- The Los Angeles area was struck by a 5.4-magnitude earthquake, shaking buildings as far away as San Diego. There were no immediate reports of injuries or damage.

The quake, originally recorded as a 5.8 magnitude, hit today at 11:42 a.m. local time, 28 miles (46 kilometers) east- southeast of the Los Angeles Civic Center, the U.S. Geological Survey said on its Web site. The quake was 8.5 miles deep and was felt more than 100 miles away.

Mayor Antonio Villaraigosa's office has received no immediate reports of injuries or damage, said spokesman Jonathan Powell in an interview. The city's fire department is also reviewing the situation.

``Everything shook,'' said Noel Jaimes, 53, a real-estate broker who was working at his home in La Mirada, 20 miles southeast of Los Angeles, when the quake hit. ``The walls were shaking, basically like if you put your hand on a piece of plywood and shake on it.''

As of 12:29 p.m. local time, 30 aftershocks had been recorded, ranging from 1.3 to 3.8 in magnitude, according to the USGS Web site.

The quake ``had only a mild impact'' on Southern California Edison Co.'s San Onofre Nuclear Generating Station, just north of San Diego, and ``we have no indications of any damage,'' said Gil Alexander, a spokesman for the utility, in an e-mail message. Southern California Edison is a unit of Rosemead, California-based Edison International. The plant is operating normally, Alexander said.

Refineries Unscathed

There was little or no impact on local refinery operations in southern California following the quake. The state ranks third in the U.S. in refining capacity after Texas and Louisiana, processing more than 2 million barrels of crude oil a day.

Six refineries operate in Los Angeles County and none reported problems. They include BP Plc's refinery in Carson, Chevron Corp.'s plant at El Segundo, Exxon Mobil Corp.'s refinery in Torrance, and three refineries in Wilmington operated by ConocoPhillips, Tesoro Corp. and Valero Energy Corp., the largest U.S. refiner.

Los Angeles International Airport suspended operations for 10 minutes to inspect its terminals and airfields for damage, spokeswoman Nancy Castles said. Normal operations have resumed. The only damage the airport found is a broken water heater in Terminal 7.

The city's Metropolitan Transit Authority is operating light rail and subway trains at restricted speed and inspecting all lines for damage, MTA spokesman Dave Sotero said. The agency hasn't suspended operations on any lines.

Phone Networks `Congested'

AT&T Inc., which provides both landline and wireless phone service in Southern California, had no reports of damage to either network from the quake, said John Britton, a spokesman for the company. Some callers have been unable to make calls, however, because of increased volume, he said.

``The networks are congested heavily because everyone tries to use the resource simultaneously,'' Britton said. ``We are seeing that, but that usually dies down within an hour or a couple hours after the incident.''

Verizon Communications Inc. also had no damage from the quake to its landline or mobile networks, said company spokesman Jon Davies.

No Tsunami

The West Coast of the U.S. is situated in a region where the Pacific and North American plates meet. These tectonic plates shift regularly, causing earthquakes that sometimes produce tsunamis. Quakes of magnitude 5 and more can cause considerable damage, depending on their depth.

No tsunami warning was issued following this quake, according to the National Weather Service's Pacific Tsunami Warning Center.

``Our state Office of Emergency Services has reached out to local governments in the affected area to ensure that levees, bridges and other critical infrastructure are inspected and declared safe,'' Governor Arnold Schwarzenegger said in a statement. ``We are activating our regional and state emergency operations centers and will continue monitoring the situation closely.''

Sergeant William Hunt at the Chino Hills station of the San Bernardino Sheriff's Department said there were no reports of injuries or structural damage in the city. Several grocery stores closed immediately after the quake to clean up broken glass from bottles that fell from shelves, he said.

The only damage at Jaimes's house in La Mirada was a glass trophy that fell off a shelf and broke, he said. Jaimes also lost telephone service for about 20 minutes, he said.

A USGS study issued in April found that California will almost certainly be hit within 30 years by an earthquake as strong as the 6.7-magnitude temblor that struck the Northridge area of Los Angeles in 1994, killing 60 people, leaving 20,000 homeless and damaging 40,000 buildings.

To contact the reporter on this story: Ryan Flinn in San Francisco at rflinn@bloomberg.net

Last Updated: July 29, 2008 16:39 EDT