RELATED: Bay Area Earthquake Tracker
The U.S. Geological Survey said the quake in the Pacific Ocean was centered about 100 miles (164 kilometers) west of Capetown, California.
The USGS reported that it struck at 8:39 a.m. at a depth of 3 miles (5 kilometers).
The Ferndale Enterprise reported on Twitter the rolling quake was felt in Ferndale, a city in Humboldt County that has many well-preserved Victorian homes.