UPDATE 2-Strong quake shakes Southern California; no immediate reports of damage

A powerful earthquake of magnitude 6.4 struck Southern California near the city of Ridgecrest, some 200 miles (320 km) northeast of Los Angeles, the U.S. Geological Survey said on Thursday.

The USGS said the quake, initially reported as a magnitude 6.6, was very shallow - only 5.4 miles (8.7 km) - which would have amplified its effect. The temblor, which was felt as far as Los Angeles, was quickly followed by several smaller aftershocks in the area.

There were no immediate reports of injuries or damage. California, is on the so-called Pacific Ring of Fire, and is prone to earthquakes.

Authorities in the Ridgecrest area could not be reached immediately for comment.