Magnitude 6.4 earthquake shakes Northern California

A magnitude 6.4 earthquake struck off the northern California coast early Tuesday morning. Preliminary data indicated that the tremor occurred at 2:34 a.m. local time. Its epicenter was about 7.5 miles southwest of Ferndale, Calif., 300 miles from San Francisco. The probability of casualties is low, but some damage may have occurred, according to information from the National Geological Survey (USGS).

No tsunami threat

As of early Tuesday morning, there was no tsunami threat stemming from the earthquake, according to the USGS warning system. The Humboldt County Sheriff's Office reaffirmed the information and added that power failures were being experienced in the area. The PowerOutage.US Power Tracker showed that 55,376 people were left without power.

Residents were instructed not to call 911 unless they were experiencing an "immediate emergency."

Senator Mike McGuire, who represents the county, tweeted that safety assessments would be conducted after the quake and that aftershocks were still continuing.