Petrolia, California – A magnitude 4.2 earthquake struck offshore early Thursday, lightly shaking parts of Humboldt County just after midnight local time.
According to the U.S. Geological Survey, the quake hit at 3:41 a.m. UTC about 56 kilometers west-northwest of Petrolia, at a depth of 10.1 kilometers. The event was reviewed and confirmed by the Northern California Seismic System.
Initial reports show weak shaking was felt along the northern California coast, including in Petrolia and neighboring communities. Twenty residents submitted “Did You Feel It?” responses, with most describing mild, brief tremors. The USGS PAGER system issued a green alert, indicating no expected damage or casualties.
While there were no immediate reports of disruptions, authorities recommend residents in seismic zones check emergency kits and review earthquake preparedness plans. Offshore quakes in this region are not uncommon due to the nearby Mendocino Triple Junction, where three tectonic plates meet.
This marks the latest seismic activity in a historically active zone. The USGS and California Integrated Seismic Network will continue to monitor the area. No aftershocks have been reported at this time.
