WASHINGTON, March 10 -- A 6.9-magnitude earthquake struck off the coast of the U.S. state of California early Monday, the U.S. Geological Survey (USGS) said.

The quake, which occurred at 0518 GMT, was located 77 km northwest of Ferndale, California, with a depth of 7 km, according to the global earthquake monitoring agency.

No damage or casualites have been reported so far.

However, China Earthquake Network Center estimated the earthquake at 7.0magnitude.

There was no threat of a "widespread destructive tsunami," the Alaska Tsunami Warning Center said.