'Biggest in decades': Powerful earthquake rocks California

A powerful magnitude 6.4 earthquake has struck southern California – the biggest in the area in 20 years.

The earthquake struck near the town of Ridgecrest, about 175km northeast of Los Angeles, sending residents into a mass panic.

The Kern County Fire Department said on Twitter it was responding to "nearly two dozen incidents ranging from medical assistance to structure fires in and around the city of Ridgecrest, CA".

Ridgecrest mayor Peggy Breedon said the town was dealing with fires and broken gas pipelines, as well as falling objects that hit people, as the town endured many aftershocks.

"We are used to earthquakes but we're not used to this significance," she told MSNBC.

"It almost gave me a heart attack," said Cora Burke, a waitress at Midway Cafe in Ridgecrest, a town of 28,000 people.

"It's just a rolling feeling inside the building, inside the cafe and all of a sudden everything started falling off the shelf, glasses, the refrigerator and everything in the small refrigerator fell over."

Video posted online of a liquor store in Ridgecrest showed the aisles filled with broken wine and liquor bottles, knocked down boxes and other groceries strewn on the floor.

There was at least one house on fire in Ridgecrest, with Ben Hood sharing footage of the blaze on Facebook.

“Huge earthquake. 6.4 they’re saying and not to mention a very nice old man down the street house caught on fire. He is OK thank God but he lost everything just about,” he wrote.

Strongest in 20 years

Veteran seismologist Lucy Jones said the earthquake on Thursday (local time) was the strongest to hit Southern California in 20 years.

The previous largest quake was a 7.1 that struck in the area on October 16, 1999, she said.

She told reporters at the California Institute of Technology in Pasadena that the 6.4 quake centred in the Mojave Desert near the town of Ridgecrest was preceded by a magnitude 4.3 tremblor about a half hour earlier.

She says it was a vigorous aftershock sequence occurring and that she wouldn't be surprise if a magnitude 5 quake occurred during the aftershocks.

"We should be expecting lots of aftershocks," she said.

People from Las Vegas to the Pacific Coast reported feeling a rolling motion and took to social media to report it.

Local emergency agencies also took to social media to ask people to only call 911 for emergencies.

"We are very much aware of the significant earthquake that just occurred in Southern California. Please DO NOT call 9-1-1 unless there are injuries or other dangerous conditions. Don't call for questions please," the LAPD said in a statement published on Twitter.

Houses shaking during Californian quake

Ashleigh Chandler, a helicopter rescue EMT at Fort Irwin, California, said the quake happened as she was getting ready for a July 4th party.

"I was just in the living room getting everything ready, we start to feel the shaking, so then I look up and then the wine bottles start rattling and I thought, 'They're going to fall’,” she said.

"My stepson was in the house and my dog, so we just got everyone outside and then it ended. It was like 15, 20 seconds, maybe. It was pretty good shaking, so I'm out of breath."

The quake comes 25 years after a 1994 magnitude 6.6 earthquake caused devastation in a heavily populated area of Los Angeles and caused billions of dollars of damage, US Geological Survey geophysicist Paul Caruso said.

The USGS said the quake, initially reported as a magnitude 6.6, was very shallow – only 8.7 km – which would have amplified its effect.

That quake struck at around 1.30pm (local time) in an area on the edge of Death Valley National Park.

It was felt throughout Los Angeles, as far north as Fresno, and as far east as Las Vegas, Nevada.

It was even felt south of the border in Mexico, where buildings were evacuated in the towns of Tijuana and Mexicali, according to Baja state officials.

With AP and AAP

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