Earthquake damage is seen outside a building on Tuesday in Rio Dell, Calif. Kent Porter/The Press Democrat via Associated Press

RIO DELL, Calif. — A powerful earthquake that residents described as “violent” rocked a rural stretch of the Northern California coast early Tuesday, leaving 11 people injured and 70,000 without power as a rain storm was about to roll in, officials said.

The magnitude 6.4 earthquake occurred at 2:34 a.m. near Ferndale, a small community about 210 miles northwest of San Francisco and close to the Pacific coast. The epicenter was just offshore at a depth of about 10 miles. Numerous aftershocks followed.

Though the region, part of California’s lightly populated, forested far north coast, is prone to earthquakes, residents described the incident as particularly jarring.

Eureka resident Dan Dixon, 40, said he and his wife were sleeping when it jolted them awake and shook everything, throwing pictures in their home to the ground. Their infant daughter, he said, slept through it.

“It was probably the most violent earthquake we have felt in the 15 years I have lived here,” he said. “It physically moved our bed.”

There was “some damage” to buildings and infrastructure in Humboldt County, and two hospitals in the area lost power and were running on generators, but the scale of the damage appeared to be “minimal” compared to the strength of the quake, according to Brian Ferguson, a spokesperson for the California Governor’s Office of Emergency Services.

The region is home to redwood forests, mountains, a port and a state university. Long before the state legalized marijuana, Humboldt was part of the three-county Emerald Triangle where clandestine cannabis production was legendary.

Approximately 11 people were reported as injured, the Humboldt County Sheriff’s Office said in an early afternoon statement. Officials noted there were two deaths as result of “medical emergencies” during or just after the quake.

Damage was mostly focused on the small communities of Rio Dell, Ferndale and Fortuna, Cal OES Director Mark Ghilarducci said during a news conference in Sacramento.

A road closure on California State Route 211 at Fernbridge, a 1,320-foot-long concrete arch bridge that spans the Eel River near Fortuna, Calif., on Tuesday in Humboldt County. The bridge is closed while they conduct a safety inspection checking for possible seismic damage. Officials say a strong earthquake in Northern California has cut off power to thousands and damaged roads and homes. Caltrans District 1 via Kent Porter/The Press Democrat via Associated Press

Ghilarducci did not have specifics on the extent of damage to structures and infrastructure, saying assessments were still underway. That included the number of homes that might be damaged badly enough to displace residents, he said.

“This is another example of the fact that earthquakes can occur at any time without notice,” he said.

Authorities closed an important bridge in Ferndale that was damaged. The state highway department tweeted a photo showing crumpled pavement.

State Sen. Mike McGuire, who represents the area, said Rio Dell, home to just a few thousand people, sustained most of the damage. He said there was one confirmed structural fire, a few structures came off their foundations, and the municipal water system was damaged, but it was unclear if any homes and businesses lost access to water.

Authorities said more than 70,000 people lost power and remained without it nearly 12 hours after the earthquake.

The power outage involved the main transmission line that runs into the region and Pacific Gas & Electric’s restoration work was slowed because rain prevented use of a helicopter to assess damage, McGuire said. The utility expected electricity to be restored by evening, but residents should be prepared for more time without power, he said.

PG&E did not immediately reply to a phone call seeking comment but tweeted that crews were responding to assess its systems “and doing everything possible to minimize power and gas outages.”

Humboldt County has about 136,000 residents and is in a part of the state that has a long history of large earthquakes, including a magnitude 7.0 in 1980 and a 6.8 in 2014, according to the California Earthquake Authority.

Caroline Titus, a resident of Ferndale, tweeted video in her darkened home of toppled furniture and smashed dishes.

“Our home is a 140-year-old Victorian. The north/south shaking is very evident in what fell,” she tweeted.

Larkin O’Leary, 41, of Santa Rosa, traveled to spend her anniversary with her husband in Ferndale, where they had been jolted by an earthquake last year. They decided to try again and booked the romance package at a historic inn, the same spot as a year ago.

O’Leary said she woke at 2:30 a.m. with an eerie feeling and tried to go back to sleep.

“I laid back down again and it was almost as if someone jumped on the bed,” she said. “It was so terrifying. … It shook in a way I had never experienced. It was up, down, all around.”

The couple quickly got out of Ferndale and returned to their home.

“Never again,” O’Leary said.

Merchandise is knocked off the shelves inside a Dollar General store after an earthquake early Tuesday morning in Rio Dell, Calif. Godofredo A. Vásquez/Associated Press

The earthquake occurred in an area known as the Mendocino Triple Junction, where three tectonic plates meet.

“We’re in this moment of geologic time where the most exciting, dynamic area of California happens to be Humboldt County and the adjacent offshore area,” said Lori Dengler, professor emeritus of geology at Cal Poly Humboldt.

Dengler said it is typical for there to be uncertainty about damage after a large earthquake. But she noted that much of the area is rural and wood frame construction is common, which in the past has helped limit damage.

The quake triggered a massive response by the West Coast’s warning system that detects the start of a quake and sends alerts to cellphones in the affected region that can give people notice to take safety precautions in the seconds before strong shaking reaches them.

The system pushed out alerts to some 3 million people in Northern California early Tuesday, Ghilarducci said. “The system did operate as we had hoped,” he said.

The earthquake came just days after a small magnitude 3.6 earthquake struck the San Francisco Bay Area, waking up thousands of people before 4 a.m. Saturday and causing minor damage.

That earthquake was centered in El Cerrito, about a 16-mile drive to downtown San Francisco.