5.6 magnitude earthquake shakes Mendocino County, triggers Northern California alerts

A 5.6-magnitude earthquake struck near Willits in Mendocino County just after 8:10 a.m., jolting Northern California and sending ShakeAlert notifications as the ground shook. The U.S. Geological Survey placed the epicenter 6.8 miles west-northwest of Potter Valley and 14.7 miles north of Ukiah, and classified it as a significant earthquake with Yellow pager alert level and estimated intensity of MMI VII, or very strong shaking.

USGS listed three smaller quakes below magnitude 2.7 near the epicenter within an hour, a sign that aftershocks remained possible. The agency also identified the event as 11 kilometers north of Redwood Valley in its significant-earthquake listing. No tsunami warning was issued.

State warning systems were part of the early response. California’s Earthquake Warning system, managed by the Governor’s Office of Emergency Services, uses ground-motion sensors to detect earthquakes and alert Californians to “Drop, Cover and Hold On” before strong shaking arrives. ShakeAlert warns that significant shaking is expected imminently, giving residents only seconds to react.

Mendocino County spokesperson Heather Rose said hospitals had reported injuries, though the county did not yet have details on their nature or severity. Willits Mayor Tom Allman was not aware of major structural damage, but power lines were down and several roadways were affected. Crews were also responding to a natural gas leak at a shopping center.

The disruption spread through daily life in Willits. Grocery stores and pharmacies were closed for cleanup, and gas stations stayed unavailable while officials inspected fuel tanks. PG&E said thousands of Mendocino County residents lost power after the quake, leaving outage maps and restoration updates as a central source of information for customers trying to gauge when electricity would return.

Mendocino County sits in one of Northern California’s most seismically active stretches, far from the Bay Area but still exposed to the same fault-driven risk. The quake was the biggest in nearly nine decades in the region.