The United States Geological Survey reports a preliminary magnitude 6.4 earthquake struck southwest of Searles Valley in San Bernardino County Thursday.

The quake hit at 10:33 a.m. local time at a depth of about 5 miles.

 This is the largest by far earthquake to hit Southern California since the 1999 magnitude 7.1 Hector Mine earthquake that struck in a remote area of the Mojave Desert and caused little damage. In 1994, the 6.7 Northridge temblor struck in a highly-populated area, resulting in 57 deaths, more than 8,700 injuries and billions of dollars in damage.

Though widely felt in the Los Angeles area, today’s earthquake was centered in a remote area; the extent of damage and injuries is unknown at this time.

“The shaking was pretty low and rolling, but it was the longest earthquake I’ve felt in Los Angles in my seven years living here,” Echo Park resident Annie Powers said. “It was long enough that I definitely started to wonder if this was the big one.”

earthquake. “We are very much aware of the significant earthquake that just occurred in Southern California. Please DO NOT call 9-1-1 unless there are injuries or other dangerous conditions. Don’t call for questions please,” LAPD said in a statement.

The Los Angeles International Airport released a statement saying all runways were inspected with no reported damage to the airfield or the Sepulveda tunnel. “Operations remain normal,” it said.

The magnitude was initially reported as 6.6 by the USGS; it was later downgraded to 6.4. The quake’s epicenter was about 11 miles east northeast of Ridgecrest, about 109 miles north of San Bernardino and 121 miles northeast of Los Angeles, according to the U.S. Geological Survey.

Aftershocks continue to rattle the area after the morning’s large quake.

More information on this earthquake is available on the USGS event page.

See the latest USGS quake alerts, report feeling earthquake activity and tour interactive fault maps in SFGATE’s earthquake section.