By Dan Whitcomb

LOS ANGELES (Reuters) - An earthquake struck just east of Los Angeles on Tuesday, rocking tall buildings and rattling nerves across Southern California, but causing no serious injuries or major structural damage.

The quake hit at 11:42 a.m. local time (1842 GMT) about 30 miles (48 km) east of Los Angeles in suburban Chino Hills and registered magnitude 5.4 -- making it the strongest seismic event centred near America's second-largest city since the 6.7-magnitude Northridge quake in 1994.

It was followed in the next few hours by more than two dozen aftershocks, the largest measuring 3.6, and geologists said there was a small chance it could be a foreshock to a larger earthquake still to come.

"I think we were very lucky with this one," Gov. Arnold Schwarzenegger told a news conference in Sacramento, adding he called his Los Angeles-area home to speak with his wife, Maria Shriver, immediately after the quake.

Magnitude 5 quakes are considered moderate but are still capable of causing damage. The U.S. Geological Survey said Tuesday's quake was shallow, about 8.5 miles (13.6 km) deep.

Across Southern California, the temblor was felt as a strong jolt, swaying tall buildings in downtown Los Angeles and Orange County and sending office workers into the streets.

"I immediately went and stood under a doorway," said Rachel Feldman, a 27-year-old attorney who works in the 75-story US Bank Tower in downtown Los Angeles, the tallest building in the western United States.

Sara Phillips, 28, also an attorney in the US Bank Tower, said: "I wasn't scared. The building is on rollers so it made me feel like I was going to barf."