https://www.mercurynews.com/2019/10/06/twin-3-5-magnitude-quakes-rattle-north-coast-waters/ > PETROLIA — Two earthquakes, each registering 3.5 magnitude, rumbled waters miles off California’s North Coast, authorities said Sunday. > The United States Geological Survey said the first quake hit at 4:17 p.m. about 16 miles off Petrolia, at a depth of just over 10.5 miles.