A 6.5-magnitude earthquake struck Thursday off the US west coast north of San Francisco, but no major tsunami threat was expected, seismologists said. The US Geological Survey said there was "a low likelihood of casualties and damage" from the quake. The epicenter of the quake, which hit at 6:49 am (1449 GMT), was located 97 miles (157 kilometers) west of Ferndale, California at a depth of 6.2 miles (10 kilometers), USGS said.