A magnitude 5.6 earthquake struck Mendocino County, Northern California, on Wednesday morning, marking the largest seismic event in the region since 1940. The U.S. Geological Survey (USGS) reported the quake occurred at 8:10 a.m. Pacific Time, with an epicenter located about seven miles southeast of Willits and approximately five miles deep. The tremor was widely felt across Northern California, reaching as far north as Humboldt County and south to Sonoma County.

The shaking caused power outages affecting more than 6,000 residents in several towns near the epicenter, according to the Mendocino County Executive Office. Items were knocked from shelves and cupboards in homes and businesses, and residents reported cracks in walls in areas such as Ukiah. Several aftershocks, none exceeding a magnitude of 2.7, followed within the hour.

Local officials and witnesses described the intensity of the quake as strong and sudden. An employee at a Safeway store in Willits reported flickering lights, falling ceiling debris, and customers rushing to evacuate. In Ukiah, cracks appeared in structures like the Coyote Valley Resort, while the city’s new hospital experienced fallen monitors. Willits Mayor Tom Allman described feeling sustained shaking lasting about eight seconds, with some coffee cups falling in a restaurant.

Heather Rose, a spokesperson for Mendocino County, confirmed that some injuries were reported but did not provide detailed information on their severity. Hospitals in the area were assessing conditions, and officials planned further updates later Wednesday. Despite the shaking and scattered damage, no significant interruptions to major infrastructure such as hospitals, water, or sewage systems were initially reported, according to state Sen. Mike McGuire and county representatives.

The quake was notable for occurring in a rural area not typically associated with major seismic activity, situated roughly 140 miles northeast of San Francisco. Seismologist Lucy Jones noted the region is not located on a major fault, adding that while earthquakes have occurred previously, none matched this magnitude in recent decades. She advised that aftershocks are expected but predicted they would likely remain relatively small.

The USGS earthquake early warning system was activated, sending alerts to cellphones throughout the San Francisco Bay Area. In total, it is estimated that between 60,000 and 70,000 people experienced moderate to very strong shaking. The California Governor’s Office of Emergency Services reported issuing nearly 657,000 earthquake warnings via the MyShake app across Northern California and was coordinating with local authorities to monitor the aftereffects and assess any further impacts.

Authorities have urged the public to stay off roads where possible to facilitate damage inspections and repair efforts, as emergency crews continue to respond to the event. The USGS has estimated a 6% chance of an aftershock reaching magnitude 5 or greater over the next week.