SAN FRANCISCO (AP) — A rural area of Northern California experienced its strongest earthquake since 1940 on Wednesday morning, but it caused only mild shaking with no immediate reports of damage or injuries.

The epicenter of the quake, with a preliminary magnitude of 5.6, was about 7 miles (12 kilometers) northwest of the agricultural town of Willits, according to the U.S. Geological Survey. It was widely felt, including in the coastal city of Fort Bragg. The initial quake was centered inland about 50 miles (80 kilometers) east of Fort Bragg at 8:10 a.m. PT, and the USGS said it was about 5 miles (8 kilometers) deep.

The area in Mendocino County dotted with small, agricultural towns is 140 miles (225 kilometers) northeast of San Francisco.

Brie Leon and colleagues had just opened Club Calpella Restaurant when the building started shaking, rattling plates and liquor bottles.

“I had just turned the open sign on and went back into the kitchen, and that’s when it happened,” she said. “It almost felt like something hit the building.”

The restaurant is in Calpella, California, a town about 10 miles (16 kilometers) south of the epicenter and in a region of Mendocino County that has been struck by smaller quakes this year.

This was the biggest earthquake in nearly nine decades in the region, which is not on a major fault, said Lucy Jones, a veteran California seismologist.

“The area is not without earthquakes, but they’re usually smaller than this,” Jones said. She added that aftershocks are likely, but they’ll “probably stay on the low side.”

Three other quakes under a 2.7 magnitude struck near the epicenter within an hour.

Leon said the quake knocked frames off the walls and bottles off the shelves in the restaurant and the stockroom next door. She and other servers were cleaning up not long after to welcome customers for breakfast.

“It wasn’t a big, big quake, but things went everywhere,” she said.

Andrea Medina, who works at Cafe One in Fort Bragg, said she, too, felt it.

“Things were shaking,” she said. “But it’s done, not too strong.”

Fawnell Dale, a dispatch supervisor at the Mendocino County Sheriff’s Office in Ukiah, described the shaking as mild and said they hadn’t gotten any reports of any damage or injuries.

Nearly 657,000 earthquake early warning alerts were sent by the MyShake App throughout Northern California, the California Governor’s Office of Emergency Services said. Cal OES had not received any reports of damage or injuries but it was coordinating with authorities to evaluate impacts, the office said in a statement.

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Weber reported from Los Angeles. Associated Press reporter Russ Bynum contributed from Savannah, Georgia.