Tens of thousands of homes and businesses along the Northern California coast remained without power Tuesday evening, nearly a day after a powerful earthquake jolted people awake and shook homes off foundations, injuring at least 12 and leaving many without water.

“It felt like my roof was coming down,” Cassondra Stoner said. “The only thing I could think about was, ‘Get the freaking kids.’”

When the ground stopped moving, Stoner’s family was fine — a daughter even slept through the racket. But when she showed up to work at Dollar General, she found tiles had fallen from the ceiling, shelves were toppled and the contents of the discount store she manages were scattered on the floor.

The magnitude 6.4 earthquake occurred at 2:34 a.m. near Ferndale, a small community about 210 miles (345 kilometers) northwest of San Francisco and close to the Pacific coast. The epicenter was just offshore at a depth of about 10 miles (16 kilometers). Numerous aftershocks followed.

Pacific Gas & Electric had restored power to about 40,000 customers — more than half of the original 72,000 that had been affected — by late Tuesday. The utility said it expected electricity to be fully restored within 24 hours.

Residents in the area known for its redwood forests, scenic mountains and the three county Emerald Triangle’s legendary marijuana crop are accustomed to earthquakes. But many said this was more violent and unnerving than the usual rolling motion they experience.

“You could see the floor and walls shaking,” said Araceli Huerta, who was still rattled some 10 hours later. “It sounded like a freight train was going through my house.”

Damage to buildings and infrastructure was still being assessed. Two Humboldt County hospitals 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.

Gov. Gavin Newsom proclaimed a state of emergency for Humboldt County on Tuesday evening.

Approximately 12 people were reported as suffering injuries, including a broken hip and head wound, the Humboldt County Sheriff’s Office said at a news conference interrupted by a jarring aftershock. Two people died — an 83-year-old and a 72-year-old — because they couldn’t get timely care for “medical emergencies” during or just after the quake.

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

In Rio Dell, a hamlet of about 3,000 people where destruction was worst, at least 15 homes were severely damaged and deemed uninhabitable and 18 others were moderately damaged, officials said after a partial assessment. They estimated that 30 people were displaced and said that number could rise to 150 after a full tally of damage.

The city’s water system was shut down for repairs for as long as two days because of leaks. Portable toilets were set up at City Hall and water was being handed out at the fire house.

A bridge over the Eel River built in 1911 that is the main route into Ferndale was damaged and closed to traffic, requiring a longer detour through the mountains to reach the quaint Victorian town, where all of Main Street is on the National Register of Historic Places.

Caroline Titus, former owner of the Ferndale Enterprise newspaper, said the quake only broke a few windows on storefronts. At her 140-year-old home, plants were knocked over, her coffee bar crashed to the floor, pictures fell off the wall and books tumbled from shelves.

“It’s all just pain-in-the-butt type of damage,” Titus said.

Since a magnitude 7.2 quake in the area in 1992 injured hundreds, sparked fires and destroyed many homes, building codes have required retrofits to make structures much more resilient to the shaking, Titus said.

Still, she said, each strong quakes evokes the same fear: “Is this the one. Is this the nine-pointer?”

In an echo of the 1992 quake, the volunteer Rio Dell Fire Department was initially delayed in responding to some 60 calls that included two fires because the garage doors were off the hinges and had to be pried open, Chief Shane Wilson said. Three decades ago, homes in nearby Petrolia burned because the firehouse garage door jammed and trapped the engines inside.

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, said state Sen. Mike McGuire, who represents the area.

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.

Dennis Leonardi drove through the night from the San Francisco Bay Area to get back to his dairy farm in Ferndale, and then had to take a lengthy detour because the bridge was out.

Leonardi spent two hours cleaning up glass after the temblor shook nearly ever drawer in his house open, knocked over a dresser and yanked furniture and appliances from where they were anchored to the wall for earthquake safety. A glass cabinet with mementos, ornaments and family photos “walked itself” away from a wall and a refrigerator and freezer “shimmied its way across” the garage.

“The cows were just dancing to some rock and roll today,” he said, noting that his herd appeared to be OK but were probably spooked by the din of everything “bouncing around.”

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.

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.

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, officials 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.