A Magnitude 5 Quake off the North Coast

A magnitude 4.96 earthquake struck in the Pacific Ocean about 69 miles (111 kilometers) west of Petrolia on Wednesday, Nov. 4, at 8:56 p.m., according to the U.S. Geological Survey. The USGS estimated the quake was shallow, and it has since drawn 145 "felt" reports to the agency.

The epicenter sat along the Mendocino Fracture Zone, the offshore boundary between the Pacific and Gorda plates that runs west from the Mendocino Triple Junction off Cape Mendocino. The USGS assigned the event its lowest "green" alert level, meaning no significant damage was expected, and people who reported feeling the quake described light shaking. The National Tsunami Warning Center said there was no tsunami danger.

The spot has shaken before. A magnitude 5.6 quake struck less than 3 miles from Wednesday's epicenter on Sunday, May 21, 2023, at 11:44 a.m., also at a green alert level, and drew 623 felt reports to the USGS.

The last major quake in these waters struck Dec. 5, 2024, about 30 miles east of Wednesday's epicenter. That magnitude 7.0 hit at 10:44 a.m. roughly 39 miles west of Petrolia and was the largest earthquake to affect the North Coast since the 1992 magnitude 7.2 Cape Mendocino quake, according to Lori Dengler, director of the Humboldt Earthquake Education Center at Cal Poly Humboldt. Five minutes after the shaking, the National Tsunami Warning Center put the coast from near Santa Cruz to central Oregon under a tsunami warning, which was canceled shortly before noon.

The nearest communities to Wednesday's quake, Petrolia and Ferndale, lie roughly 70 miles east of the offshore epicenter, recorded at 40.41°N, 125.59°W.