Southern California jolted by large aftershock

A strong aftershock has shaken southern California as residents were still assessing the damage from the strongest earthquake in the region in 25 years.

The 5.4 magnitude aftershock, the biggest so far, struck early on Friday in the same desert region as Thursday's earthquake.

Its epicentre was about 18km west of Searles Valley, the US Geological Survey said.

The aftershock was felt 240km to the south in Los Angeles and the surrounding area, with many residents posting on Twitter that they were awakened by it.

There had already been more than 80 smaller aftershocks since Thursday's 6.4 magnitude quake near the city of Ridgecrest, which was felt from Los Angeles to Las Vegas, USGS seismologist Lucy Jones said.

Only a few injuries were reported in Thursday's quake, but two houses caught fire from broken gas pipes, according to officials.

Water gushed out of zigzagged cracks in the pavement from ruptured water lines and deep fissures snaked across the Mojave Desert, with people stopping to take selfies while standing in the rendered earth.

The quake sent 30 residents of the desert community of 28,000 to emergency shelters, knocked some houses off their foundations and left many homeowners wondering if their insurance would cover the damage, Ridgecrest Mayor Peggy Breeden said.

"The most important thing is that we have not had any loss of life or any major personal damage to people," Breeden told CNN on Friday.

Breeden said officials were still assessing the extent of the damage, but added that emergency state and federal aid would enable the city's overwhelmed agencies to start the cleanup without worrying about their budgets.

The quake is the largest in southern California since a 1994 magnitude 6.6 earthquake struck a heavily populated area of Los Angeles, killing 57 people and causing billions of dollars of damage.

Reuters