A 5.6-magnitude earthquake struck near Willits in Mendocino County on Wednesday morning — the most powerful temblor to hit the area in nearly nine decades — injuring residents, cutting power to thousands, and pushing earthquake alerts to phones across the Bay Area and beyond.

The quake is an unusual geological event: the Willits region sits off California's major fault systems, making seismic activity of this scale exceptionally rare. The USGS assigned a yellow PAGER alert — its second-highest tier for potential losses — and community seismometers recorded intense shaking more than 100 miles from the epicenter. With aftershocks still possible, communities from Mendocino County to the North Bay are assessing what the earth left behind.

The United States Geological Survey recorded the quake at magnitude 5.59 — rounded to 5.6 in public advisories — shortly after 8:10 a.m. Wednesday, with an epicenter roughly 11 kilometers north of Redwood Valley and about 15 miles north of Ukiah. The agency's "Did You Feel It" crowd-sourced intensity map logged more than 5,100 felt reports within hours of the strike, and its ShakeMap estimated "Very Strong" shaking near the epicenter. USGS assigned the event a yellow PAGER alert, indicating the potential for injuries and economic losses reaching into the millions.

Lucy Jones, a veteran California seismologist, told NBC Bay Area the quake was the biggest to hit this part of the state since 1940 — an 86-year gap that underscores how unusual Wednesday's event was. "The area is not without earthquakes, but they're usually smaller than this," Jones said. She noted the region does not sit on a major fault line, and added that while aftershocks are likely, they would "probably stay on the low side." Within an hour of the main event, USGS recorded three additional temblors near the epicenter, all below magnitude 2.7.

In Willits, the commercial corridor felt the brunt of it. Both Grocery Outlet and Safeway closed temporarily for safety inspections and structural repairs. NBC Bay Area reporters on the scene documented damage to an auto parts store and a home where a chimney had collapsed. Authorities responded to a report of a natural gas leak at a local shopping center. Gas stations remained shuttered while officials inspected fuel tanks.

Mayor Tom Allman, speaking with NBC Bay Area from Willits, said he was not aware of "major structural damage" to city infrastructure. He described the experience as a sustained rolling motion — "five or six seconds" — that downed power lines across several roadways and set local fire and police crews scrambling. In the immediate aftermath, grocery stores and pharmacies remained closed while cleanup was underway.

Injuries were confirmed by the Mendocino County Executive Office, though no deaths were reported. County spokesperson Heather Rose said hospitals had taken in patients following the quake, but she said officials had no details yet on the nature or extent of those injuries. A fuller accounting, she said, would come after officials convened later Wednesday.

Pacific Gas & Electric reported thousands of customers without power across Mendocino County in the quake's wake, with restoration expected between 1:30 and 3:30 p.m., according to the utility's outage tracker.

The earthquake was felt far beyond Mendocino County. California's Governor's Office of Emergency Services said nearly 657,000 Earthquake Early Warning alerts were dispatched via the MyShake App — reaching Bay Area residents more than 100 miles to the south, many of whom reported shaking lasting up to 30 seconds. Governor Gavin Newsom was briefed on the situation and his office said it was coordinating with emergency officials to assess damage and impacts.

The National Tsunami Warning Center confirmed no tsunami danger from the event.

For a region not defined by seismic risk the way the Bay Area is, Wednesday's quake served as a reminder that California's geological hazards don't confine themselves to the well-mapped faults. Jones noted aftershocks are expected to remain minor — but what's already done will take time to fully measure.