A 7.1 magnitude earthquake has rattled parts of Southern California, the biggest tremor to strike in 20 years.
It struck at the shallow depth of 0.9km (0.6 miles) and its epicentre was near the city of Ridgecrest, about 240km north-east of Los Angeles.
A 6.4-magnitude quake hit the same area on Thursday at a depth of nearly 11km.
Seismologist Dr Lucy Jones said the quakes could continue. "This is an earthquake sequence," she said at a press conference. "It will be ongoing."
"Every earthquake makes another earthquake more likely," she added, saying there was a 10% chance of a similar or even larger quake following in the next week.
However, Dr Jones said it was not likely the quake would trigger shocks on other fault lines.
The earthquake was felt as far away as Las Vegas in the neighbouring state of Nevada and over the border in Mexico.
California Governor Gavin Newsom offered his "heartfelt support" to all those affected, and has requested a Presidential Emergency Declaration and federal aid to help.
What's the damage?
Fires have broken out and emergency services are responding to calls across the state after the quake.
"We've got fires, we've got gas leaks, we've got injuries, we've got people without power," Ridgecrest Mayor Peggy Breeden told Reuters news agency. "We're dealing with it as best we can."
Kern County Fire Department chief David Witt said about 1,800 people had no power after the quake, but added there were "nothing but minor injuries... such as cuts and bruises, by the grace of god".
The San Bernardino County Fire Department said reports suggested "damage is more significant than yesterday's quake", and said they were tackling blazes and gas leaks.
Officials said it was still unclear how much damage had been caused and how many people had been injured in the state.
"It was bad. Man. It hasn't stopped yet," local resident Jeremiah Jones told the Los Angeles Times.
Thursday's event wrecked some homes in the region.
The Los Angeles Fire Department however said nobody had been killed or injured. A statement after the latest quake said the authorities had seen "no major infrastructure damage" after a survey of the city.
Crowds at a Los Angeles Dodgers baseball game were seen leaving their seats when the quake struck, although the players themselves continued playing.
A US Navy weapons testing station near Ridgecrest was also affected.
NAWS China Lake - the Navy's single largest landholding, covering an area larger than the state of Rhode Island - announced on Facebook it is "not mission capable until further notice", without providing details.
In Las Vegas, a basketball match between the New York Knicks and the New Orleans Pelicans was abandoned because of the tremors.
LA Mayor Eric Garcetti said he was sending a task force to Kern County "to help with the damage closer to the epicenter".-BBC