Emergency rescue crews fanned out yesterday to assess damage from the second powerful earthquake to hit Southern California in as many days - a 7.1 magnitude tremor that revived fears of the so-called Big One the region has feared for decades.

No fatalities or serious injuries have been reported from this second quake, the largest in Southern California in more than two decades. It hit Friday night in a remote and sparsely populated area around 150 miles (240 kilometers) northeast of Los Angeles, where it was also felt.

But the earth's mighty twitch shook buildings, damaged roads and rattled people still jittery from a 6.4-magnitude earthquake in the same region on Thursday.

Around 3,000 people in the Mojave Desert town of Ridgecrest and the surrounding area are without power, the local utility company said.

In the town of Trona some buildings collapsed, gas pipelines ruptured and power was knocked out. Officials would know more as day breaks, said Mark Ghilarducci, director of the California governor's Office of Emergency Services.

There were "significant reports" of fires caused by gas leaks, as well as breaks to power, water and communications lines in the region, he told a press conference.

California Governor Gavin Newsom said he had requested emergency federal assistance from the White House, and state resources have been activated at their "highest level."

Newsom later declared a state of emergency for San Bernardino County, expanding on an earlier announcement covering Kern County, near the epicenter of both the quakes this week.

The latest quake was 11 times stronger than the 6.4-magnitude quake "foreshock" the previous day, according to the United States Geological Survey.

The two major quakes, along with multiple aftershocks, have revived fears of the "Big One" -- a powerful tremor along the San Andreas Fault that could devastate major cities in Southern California.

"This is an earthquake sequence. These earthquakes are related," said Caltech seismologist Lucy Jones.

There was a 10 percent chance of Friday's quake being followed by another magnitude 7.0 or higher quake in the next week, she added.

In Kern County, where the quake struck near the town of Ridgecrest, some 1,800 residents were without power, fire department chief David Witt said.

"As for injuries reported, nothing but minor injuries and such as cuts and bruises, by the grace of God," he said.

Numerous gas leaks were reported near the epicenter, including the towns of Trona and Argus.

"Firefighters have secured leaks where possible and evacuated residents from homes with leaks that cannot be secured," the San Bernardino fire department tweeted.

In Los Angeles, the fire department deployed vehicles and helicopters, and reported fallen power lines and localized electricity outages.

But Mayor Eric Garcetti said there were no reports of serious damage in the city.

Numerous visitors to Disneyland in Anaheim reported on Twitter that rides were shut for safety inspections after the quake.

No damage was reported at Los Angeles International Airport following inspections.

In Las Vegas, 150 miles east of the quake, an NBA summer league game was postponed when the tremor hit, causing the scoreboard and several overhead speakers to sway.

The earthquake was the largest in Southern California since 1999 when a 7.1-magnitude quake struck the Twentynine Palms Marine Corps base, according to The Los Angeles Times.

The latest tremor sent Ridgecrest residents fleeing outside for safety as aftershocks continued, with one woman saying she was "not comfortable" about heading back inside for the night.

The shaking stops "for a minute, and then it starts rolling again... It's pretty bizarre. But now at the moment, I'm not comfortable inside," said Jessica Kormelink.

"I was actually in the car with my mom. And it just started bouncing up,” Jessica Weston, a journalist at the Ridgecrest Daily Independent, told CNN.