A huge 6.4-magnitude earthquake struck off the coast of Northern California in the early hours Tuesday — cutting off power to 70,000 people, damaging buildings and cracking bridges and roads.

The “notable” quake struck at 2:34 a.m. around seven miles west-southwest of Ferndale, a town of about 15,000 people 261 miles north of San Francisco, officials said.

It triggered an early-warning “shake alert,” giving 3 million people in a wide surrounding area an emergency warning 10 seconds before it actually hit, officials said at a later press conference.

At least 80 aftershocks followed in the next few hours, including a powerful 4.6-magnitude one near the town of Rio Dell.

Emergency services in Humboldt County, which covers both Rio Dell and Ferndale, reported “widespread damages to roads and homes.” At least 72,000 people lost power and some areas had gas leaks.

However, there were no reported deaths — and any injuries appeared to be minor, officials said at a press conference almost nine hours later.

The damage included a bridge that is one of only a few ways into Ferndale that had to be closed to everything but emergency vehicles as photos showed a giant crack across it with broken pavement.

An emergency $6 million grant was issued to fix the 1911 structure — which is affectionately known as the “Queen of Bridges” — as officials continued to survey the damage.

At least four roads were also closed because of large cracks, with one section reportedly sinking, highway officials said.

A former local newspaper editor, Caroline Titus, shared video of items strewn around her shaken home in the early hours

“That was a big one,” she wrote — exactly a year to the day she shared similar footage during a 6.2-magnitude quake that hit Dec. 20, 2021.

“Home is a mess,” she wrote of her “140-year-old Victorian.”

Earl Brizee had only moved into his new home in neighboring Eureka on Monday, hours before the quake struck.

“I really thought, ‘Oh God, I just bought this house, I just moved in and now it’s gonna collapse on me,'” he said of the “really strong shake.”

Larkin O’Leary, 41, of Santa Rosa, was awoken during a romantic weekend at a historic inn in Ferndale — where she and her husband returned to despite being jolted awake by the quake last December.

 “It was so terrifying. … It shook in a way I had never experienced. It was up, down, all around,” she said.

“Never again,” O’Leary said after fleeing Ferndale as soon as they could.

Humboldt County, home to about 136,000 residents, is no stranger to quakes, including a magnitude 7.0 in 1980 and a 6.8 in 2014.

Still, Eureka resident Dan Dixon, 40, said it was “probably the most violent earthquake we have felt in the 15 years I have lived here.”

“It physically moved our bed,” he said of he and his wife being shaken awake — while their infant daughter snoozed through it.

The earthquake came just days after a small magnitude-3.6 earthquake struck the San Francisco Bay Area, waking up thousands of people at 3:39 a.m. Saturday and causing minor damage. That one was centered in El Cerrito, about a 16-mile drive from downtown San Francisco.

With Post wires