LOS ANGELES - A 6.3 magnitude earthquake struck the sea area 250 kilometers southwest off the coast of Southern California early Friday morning, the US Geological Survey (USGS) reported.

The quake happened at 2:36 a.m. local time (1036 GMT), followed by a 4.7 magnitude quake in 15 minutes. The nearest city from the epicenter is Avalon.

No casualty report or tsunami warning has been released so far.

The local media WABC News reported Friday morning that some residents in Long Beach, Newport Beach, Santa Ana and Temecula said they felt some shaking.

The depth of the quake is 11.3 kilometers. It is a result of shallow faulting within the oceanic lithophere of Pacific plate, as the location is some 400-450 kilometers west-southwest of the plate boundary between the Pacific and North America plates.

At the location of this event, the Pacific plate moves to the northwest with respect to the North America plate at a velocity of approximately 54 mm per year, the USGS said.