Los Angeles, July 7 (IANS) Officials have continued assessing the damages caused by a magnitude 7.1 earthquake that rocked Southern California, sending tremors that could be felt in Los Angeles, Las Vegas, and nearly 400 miles north in capital Sacramento.

The quake on Friday night caused fires, power outages and collapsed buildings, reports Efe news.

The powerful quake struck at around 8.20 p.m. on Friday night and was centred near Ridgecrest, a community of 29,000 people on the eastern side of the Sierra Nevada where a 6.4 temblor had hit on Thursday morning.

Friday's quake lasted about 30 seconds and was the strongest in Southern California in 20 years. Thousands of aftershocks followed.

Mark Ghilarducci, the director of the California Governor's Office of Emergency Services, told the media on Saturday that state officials didn't yet have a full tally of injuries from the quake but most were minor to moderate.

About 200 people stayed in shelters on Friday night because of the earthquake and aftershocks, he said.

State and local emergency responders spent Saturday carrying out systematic assessments of property structures and checking for gas leaks in communities near the epicentre.

Transportation officials have also been able to reopen roads that had been damaged or had closed because of rock slides.

The overall damage from the earthquake wasn't as severe as what officials had anticipated.

"The damage that we are seeing this morning in the light is not as extensive as one could have expected," Mr. Ghilarducci said. Still officials were monitoring the weather to ensure that wildfires wouldn't break out.

In response to Friday's quake, Governor Gavin Newsom formally requested a presidential emergency declaration for direct federal assistance to aid the affected communities.

The governor also declared a state of emergency in San Bernardino County, where Trona, a community of about 1,800 people, is located.

The town, about 25 miles east of Ridgecrest, suffered significant damage and fires in Friday's earthquake, according to state and local officials. The governor had previously declared a state of emergency for Kern County, where Ridgecrest resides, after Thursday's quake.

Over the next week there is a 3 per cent chance that an even more powerful earthquake could come and an 11 per cent chance that an earthquake nearly as powerful could come, said Robert de Groot, a scientist at the US Geological Survey.

The USGS said in a statement Saturday that millions of people in the region felt the shaking from the latest quake. The federal agency said it issued a red alert for economic losses from the quake, estimating the financial toll to be at least $1 billion.

The 7.1 magnitude earthquake on Friday was 11 times stronger than the 6.4 magnitude quake that hit on Thursday, said Mark Benthien, spokesman for the Southern California Earthquake Centre at the University of Southern California.

Friday's quake rocked buildings in Los Angeles, interrupted a Los Angeles Dodgers game and led Disneyland to evacuate rides.

Kern County Fire Department Chief David Witt said during a press conference Saturday that local responders were going from house to house in Ridgecrest to inspect properties, but so far they hadn't found major collapses or anyone trapped.

University of Michigan Professor Ben van der Pluijm, who teaches in the Department of Earth and Environmental Science, said the two earthquakes are related but occurred within two nearby fault systems. That might explain why two relatively large quakes happened in such a short period time.

The activity doesn't indicate a higher risk for a very large earthquake along the San Andreas fault, which is about 100 miles west from the eastern California shear zone, where these took place.

--IANS ksk