From the Los Angeles Times
Small earthquake rattles Los Angeles area
By Monte Morin
Los Angeles Times Staff Writer
8:41 PM PST, January 8, 2009
A 4.5 magnitude earthquake centered about a mile south of San Bernardino jolted Southern California briefly at about 7:50 p.m. Thursday evening, according to the U.S. Geological Survey and the Southern California Earthquake Center.
The quake was felt in downtown Los Angeles, parts of the High Desert, San Pedro and and coastal and inland Orange County, but was not felt as far south as San Diego. There were no immediate reports of damage, according to authorities.
"We felt the jolt, whatever time it came in, but we haven't had any reports of damages yet," said Rancho Cucamonga fire Capt. Ty Harris, whose station was built more than 50 years ago. "Our building is fairly old, and cinder block, and it shook pretty good here," he said.
Closer to the origin of the quake, Cal State San Bernardino Professor Dale Sechrest said the shaking lasted roughly 15 seconds. "Nothing fell over, nothing fell off the shelves," he said.
"Wow, we heard rumbling noise before the shock waves hit our home in Ontario," one reader wrote on a San Bernardino Sun message board.
The shaking was lighter -- but still strong -- in Orange County. "We felt it here in Yorba Linda. Shook the house for about 5-6 seconds. Nothing much except rattling but clearly an earthquake," a reader said on The Times' quake report board.
The USGS originally believed the quake measured 5.0. But officials later downgraded it to 4.5.
Earthquake experts have long said San Bernardino is particularly vulnerable to a massive temblor -- the type many times stronger than Thursday's quake.
San Bernardino lies between two of the state's most active earthquake faults, the San Andreas and the San Jacinto. Moreover, much of the city was built above a huge underground water basin.
Experts say this loose soil could liquefy in the event of a massive quake, causing buildings to topple. As of 2005, about 100 unreinforced masonry buildings in the city lacked any form of retrofitting, according to city and state records.