A moderate earthquake struck the Los Angeles area late Wednesday night, swaying high-rise downtown buildings, causing thousands of dollars in damage to a Malibu market and slightly injuring at least four people.

The quake struck four minutes before 11 p.m. and was felt from northern San Diego County 100 miles south of Los Angeles to Santa Barbara about 100 miles to the north.Seismologists at Caltech in Pasadena said the quake was centered about 8 miles south of Malibu in Santa Monica Bay and had a preliminary reading of about 5 on the Richter scale, which is strong enough to cause minor damage in urban areas.

Several dozen aftershocks followed over the next two hours, with the largest measuring 3.3 on the open-ended scale, Caltech seismic analyist Riley Geary said.

The quake shook downtown office buildings with a rolling motion for 10 to 15 seconds, but was felt as a sharp jolt closer to the epicenter.

Four people were treated for cuts and other minor injuries at Daniel Freeman Marina Hospital and St. John's Hospital, including a woman who broke her foot when she jumped out of bed, hospital officials said.

The Department of Water and Power said more than 90,000 people were temporarily without electricity because of automatic shutdowns of some equipment due to the quake.

People in Malibu, west of downtown Los Angeles, said the quake was felt as a sharp jolt and apparently knocked rocks down from the mountainside and onto the road through Malibu Canyon.

The temblor toppled bottles and jars from shelves at a Hughes' Market in Malibu, causing several thousand dollars damage to merchandise in the store, manager Kelly Seidel said.

In Santa Monica, the quake shattered a 10-foot by 15-foot storefront window at J.C. Penney in the Third Street Mall and caused a few small cracks in the stucco at City Hall, police Lt. Roy McGinnis said.