The quake was centered about 4 miles north of Big Bear City, a mountain resort town about 90 miles east of downtown L.A.
Attorney Steven De Salvo was working on a brief on the 15th floor of a downtown office building when the quake hit.
"I'm tired, trying to stay awake, and this definitely jolted me awake," he said. "The shades were kind of rocking back and forth, there was kind of a low rumble. The walls were vibrating. I've never been in a skyscraper in an earthquake before. It lasted I would say about ten to 15 seconds."
The quake was followed by a magnitude-4.5 one minute later and a magnitude-4.2 after another minute. Several aftershocks were recorded in the magnitude-3.8 and below range.
A San Bernardino County sheriff's dispatcher said he had received numerous calls inquiring about the quake but had no immediate reports of injury or damage.
Seismologist Kate Hutton, at the California Institute of Technology seismology laboratory in Pasadena, said the main quake did not appear to be an aftershock of any previous quake. It appeared to be a new earthquake sequence in an area well known for seismic activity.
She said there did not appear to be any link to the deadly 1992 Landers-Big Bear quakes. The magnitude-7.3 Landers quake on June 28, 1992, was followed a few hours later by a magnitude-6.5 quake in Big Bear mountain area.
The Landers quake toppled a chimney that killed a 3-year-old. The quakes injured more than 400 people and caused nearly $100 million in damage. There have been more than 50,000 aftershocks.