LOS ANGELES — A 6.4 magnitude earthquake struck Southern California on Thursday, the largest temblor to hit the region in two decades.

The 10:33 a.m. Pacific quake was centered in the Searles Valley, a remote area of Kern County about 100 miles north of Los Angeles, and was felt as far away as Long Beach and Las Vegas.

There were no immediate reports of fatalities, though authorities in the city of Ridgecrest were responding to dozens of emergency calls.

The quake was the largest in Southern California since the 7.1 Hector Mine quake struck the Twentynine Palms Marine Corps base in 1999.

Caltech seismologist Lucy Jones, California’s foremost earthquake expert, told a midday press conference in Pasadena to anticipate more shaking on the Fourth of July.

“We should be expecting lots of aftershocks,” Jones said.

The Kern County Fire Department was responding to “nearly two dozen incidents ranging from medical assistance to structure fires in and around the city of Ridgecrest,” according to the department’s Twitter account.

Mark Leach, an engineer who lives in the city, was in his garage about to drive to a Fourth of July barbecue in Los Angeles when the shaking started. It felt like it went on for 30 seconds, he said.

“About halfway through it I dashed out into the road completely freaking out,” he said. “You can see some cracking in the seams of the drywall and stuff was knocked off the shelves — books and CDs and stuff.”

As the aftershocks started, Leach said he could actually hear them before he felt the shaking.

The quake was relatively deep, occurring more than five miles underground.

“I was in my kitchen trying to get some coffee and all the windows started rattling,” said Emma Gallegos, a 34-year-old journalist in southwest Bakersfield. “It was just a little bit at first — I thought something was going by, and then I realized all the windows were rattling. It was kind of a long gentle roll and I felt two distinct waves.”

Gallegos said that the dried chiles hanging from a hook on her kitchen wall were all shaking. “It was surreal.”

California has been in an earthquake drought, Jones said, but Thursday’s quake does not make the “big one” any less likely.

“There is about a 1 in 20 chance that this location will be having an even bigger earthquake in the next few days, and that we have not yet seen the biggest earthquake of the sequence,” she said. “Some aftershocks will probably exceed magnitude 5, which means they’ll probably be damaging.”

She added, “We should always be preparing for the big one.”

The earthquake was centered roughly 80 miles northeast of a stretch of the 106-year-old Los Angeles Aqueduct spanning the San Andreas fault.

“Aqueduct personnel have been deployed as part of our standard earthquake response protocols to inspect the aqueduct and reservoirs,” said Joe Ramallo, a spokesman for the Los Angeles Department of Water and Power. “In the city, critical facilities are also being checked.”

“There is no information nor reports of damage at this time,” he said.

Other people nearer to the epicenter were shocked by the shaking.

“I was laying down in my bed and I had my feet on the wall and I felt like both of the sides of the house were moving and shaking so I ran, and grabbed my brother and kid and came outside,” said Edith Mata, 22, a student at Bakersfield College. Her son is 3 years old and her brother is 17.

“The neighbors across the street were also outside with their whole family of five people. My kid had no idea what was going on.” Mata said that it felt very “creepy” and that she had never experienced anything like it before.

In the Los Angeles area, the quake was slow and steady, lasting about 30 seconds.

The earthquake was centered 10 miles northeast of Ridgecrest, a city of about 29,000 known as a small town for skiers and snowboarders headed from Los Angeles to Mammoth.

The earthquake was felt widely throughout the Los Angeles area, said Caltech seismologist Egill Hauksson.

Thursday’s quake was slightly weaker than the 1994 6.6 Northridge quake, which killed dozens and caused billions of dollars in damage. But that Los Angeles quake hit in the center of a populated area, while Thursday’s quake was located in a far less developed area.

Los Angeles Times