5.6 earthquake shakes Mendocino County, triggers Northern California alerts

A magnitude 5.6 earthquake struck 11 kilometers north of Redwood Valley in Mendocino County at 8:10:40 a.m. Pacific time, triggering ShakeAlert notifications across Northern California. The U.S. Geological Survey said the quake was 8.9 kilometers deep and assigned it a yellow PAGER alert level, signaling that some damage was possible but likely localized.

The USGS estimated that about 80,000 people experienced moderate to very strong shaking, measured as MMI V to VII, while roughly 10 million people felt weaker shaking from MMI II to IV. The agency identified the quake as the potential mainshock of a sequence that already included 45 total events. Shaking was felt across Willits, Redwood Valley and Ukiah, and the day’s real-time earthquake map also showed other smaller quakes in the same part of Northern California.

The hardest immediate impacts were in and around Willits, where emergency crews responded to downed power lines, possible gas leaks and reports of water line breaks. More than 8,000 customers lost power, while businesses in the area stayed closed or operated with limited service. There were injuries but no major damage, and some hotels and homes saw interior damage including broken wine bottles, scattered items and cracked walls.

Aftershocks remained the next concern. The USGS put the odds of at least one magnitude 3 or greater aftershock in the next week at 77 percent, with a 15 percent chance of a magnitude 4 or greater event and a 2 percent chance of a magnitude 5 or greater aftershock. At least three aftershocks followed, all below magnitude 2.7. The event is being monitored by the California Integrated Seismic Network, including UC Berkeley and USGS Menlo Park.