Petrolia, California – A magnitude 3.7 earthquake struck off the Northern California coast at 1:26 p.m. local time, jolting areas near the remote Lost Coast just hours after a stronger magnitude 4.7 mainshock hit the same region earlier in the day.
According to the U.S. Geological Survey, the 3.7 quake occurred about 62 kilometers west of Petrolia at a shallow depth of less than 1 kilometer, indicating it is likely an aftershock tied to the earlier 4.7 event recorded at 10:41 a.m. roughly 57 kilometers offshore. That mainshock registered slightly deeper at 1.7 kilometers and has been identified as the primary event in this sequence.
The quakes were centered near the seismically active Cape Mendocino region, where the Pacific, Gorda, and North American tectonic plates meet. Communities across Humboldt County, including Petrolia, Ferndale, and parts of Eureka, may have felt light shaking, though no immediate damage or injuries have been reported.
Landmarks near the epicenter include the rugged Lost Coast Trail and areas south of Redwood National Park, both known for limited infrastructure and low population density. Still, residents and visitors are urged to remain alert, especially in coastal zones where rockfalls or minor landslides can follow shallow seismic activity.
Emergency officials advise checking emergency kits, securing loose items, and avoiding unstable cliffs along coastal highways such as Mattole Road. While the aftershock was weaker, the sequence underscores ongoing seismic movement in the region.
Aftershocks may continue through the day and into tonight, with additional minor quakes possible. Authorities continue monitoring the situation, and updates will follow if activity escalates.
