Mendocino 5.6 Quake Injures Residents, Knocks Out Power and Water for Thousands

Q: This earthquake struck a northern branch of the Hayward Fault. Does this relieve pressure or raise the risk for the Bay Area?

It does not meaningfully “relieve pressure” on the Bay Area’s Hayward Fault, and in the short term it may slightly change stress on nearby connected faults, though not in a way that clearly raises Bay Area danger. The Mendocino County quake appears to have struck the Maacama Fault, a northern part of the broader Hayward-Rodgers Creek-Maacama system. Seismologists generally caution that earthquakes do not act like a simple pressure valve for an entire fault network. A magnitude 5.6 releases energy locally, but it is far too small and too far north to drain the accumulated strain that worries scientists on the main Hayward Fault in the East Bay. Experts describe these faults as part of a diffuse plate-boundary zone, where stress is distributed across many faults. That means one quake can slightly redistribute stress, sometimes increasing it on one segment and decreasing it on another. But those changes are usually subtle, and there is no evidence from this event alone that the Bay Area’s immediate earthquake risk has sharply increased. The broader Bay Area hazard remains what it was before: the Hayward Fault is still considered one of the region’s most dangerous faults and is thought to be carrying substantial long-term strain. The Willits quake is notable because it was the largest on that fault section in roughly 75 years, but it should be seen mainly as a reminder that the whole northern California fault system is active, not as a sign that the Bay Area is now safer.

3 articles · Updated · KGO-TV · Jun 24

Some injuries but no deaths were reported after a 5.6 earthquake struck near Willits, with power and water outages hitting thousands and damage appearing widespread but mostly minor.
At least a dozen aftershocks followed, most below magnitude 2.5, after the quake was downgraded from an initial magnitude 6 and centered in a relatively unpopulated area north of Ukiah.
Willits and nearby stores showed the clearest disruption—items were thrown from shelves, several groceries shut down, and PG&E's outage map showed community-wide power losses.
Governor Gavin Newsom was briefed and state and local officials were assessing damage, while State Sen. Mike McGuire said there were no early signs of major damage to hospitals, sewer systems or other public infrastructure.
The shaking was felt across parts of the Bay Area as far south as San Jose, extending the impact of what earlier reports described as the area's strongest quake in decades.