By JOHN ANTCZAK and CHRISTOPHER WEBER

LOS ANGELES (AP) — Rattled residents cleaned up and officials assessed damage Monday from two of the biggest earthquakes to shake California in decades as scientists warned that both should serve as a wake-up call to be ready when the long-dreaded “Big One” strikes.

It could be several more days before water service is restored to the desert town of Trona, where officials trucked in portable toilets and showers, said San Bernardino County spokesman David Wert.

Ten residences in Trona were red-tagged as uninhabitable and officials expect that number to rise as inspectors complete surveys. Wert said he’s seen homes that shifted 6 feet (nearly 2 meters) off their foundations.

Electricity was restored to Trona over the weekend, allowing people to use much-needed air conditioners as daytime temperatures approached 100 degrees (38 Celsius).

Teams will need several more days to finish assessments in nearby Ridgecrest, where the number of damaged buildings will likely be in the dozens, Kern County spokeswoman Megan Person said.

There were 100 people at Ridgecrest’s main shelter as of Sunday afternoon, Person said. Another 43 evacuees were camped out on a lawn outside, afraid to go indoors. Person says officials are bringing in counselors to help residents still on edge as aftershocks rattle the area.

A dozen small earthquakes, each more than a magnitude 3, rattled the area overnight, according to the U.S. Geological Survey.

They were among about 3,000 aftershocks following the magnitude 6.4 earthquake Thursday and a magnitude 7.1 quake Friday centered near Ridgecrest, about 150 miles (241 kilometers) from Los Angeles.

California is spending more than $16 million to install thousands of quake-detecting sensors statewide that officials say will give utilities and trains precious seconds to shut down before the shaking starts.

Gov. Gavin Newsom said it’s time residents did their part by mapping out emergency escape routes and preparing earthquake kits with food, water, lights and other necessities.

Seismologists said a similar-sized quake in a major city such as San Francisco, Los Angeles or San Diego could collapse bridges, buildings and freeways, as well as spark devastating fires fueled by ruptured gas lines.

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Associated Press photographer Marcio Jose Sanchez in Ridgecrest and writers John Rogers and Robert Jablon in Los Angeles, Amy Forliti in Minneapolis and Courtney Bonnell in Phoenix contributed to this story.

By JOHN ANTCZAK and OLGA R. RODRIGUEZ

LOS ANGELES (AP) — The strongest earthquake in 20 years shook a large swath of Southern California and parts of Nevada on the July 4th holiday, rattling nerves and causing injuries and damage in a town near the epicenter, followed by a swarm of ongoing aftershocks.

The 6.4 magnitude quake struck at 10:33 a.m. Thursday in the Mojave Desert, about 150 miles (240 kilometers) northeast of Los Angeles, near the town of Ridgecrest, California.

Multiple injuries and two house fires were reported in the town of 28,000. Emergency crews dealt with small vegetation fires, gas leaks and reports of cracked roads, said Kern County Fire Chief David Witt.

Ridgecrest Mayor Peggy Breeden said that utility workers were assessing broken gas lines and turning off gas where necessary.

A widely felt magnitude 5.4 quake before dawn Friday was the strongest aftershock thus far. Seismologists had said there was an 80 percent probability of an aftershock of that strength within a week.

The local senior center was holding a July 4th event when Thursday’s big quake hit and everyone made it out shaken up but without injuries, she said.

“Oh, my goodness, there’s another one (quake) right now,” Breeden said on live television as an aftershock struck.

Breeden noted at a news conference that other nearby governments have offered to help the recovery effort.

President Donald Trump said he was fully briefed on the earthquake and that it “all seems to be very much under control!”

Police and fire officials said at a news conference Thursday afternoon that they have enough resources so far to meet needs in the wake of the earthquake.

California Highway Patrol Lt. John Williams said officials have found cracks on several roads in the county, but overpasses and underpasses are in good shape.

“It almost gave me a heart attack,” said Cora Burke, a waitress at Midway Cafe in Ridgecrest, of the big jolt. “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. Flames were seen shooting out of one home in the community.

Lucy Jones, a seismologist with the California Institute of Technology’s seismology lab, said the earthquake was the strongest since a 7.1 quake struck in the area on October 16, 1999.

“This has been an extremely quiet abnormal time,” Jones said. “This type of earthquake is much more normal … The long term average is probably once every five or 10 years somewhere in Southern California.”

Jones said that the 6.4 quake was preceded by a magnitude 4.2 temblor about a half hour earlier.

The epicenter was in the arid expanse of Searles Valley, a sparsely populated region.

“This is an isolated enough location that that’s going to greatly reduce the damage,” she said.

The quake was detected by California’s new ShakeAlert system and it provided 48 seconds of warning to the seismology lab well before the shaking arrived at Caltech in the Los Angeles suburb of Pasadena but it did not trigger a public warning through an app recently made available in Los Angeles County.

USGS seismologist Robert Graves said the ShakeAlert system worked properly.

Graves said it calculated an intensity level for the Los Angeles area that was below the threshold for a public alert. The limits are intended to avoid false alarms.

Glenn Pomeroy, the head of California’s Earthquake Authority, said the earthquake is “an important reminder that all of California is earthquake country.”

Pomeroy urged the estimated 2,000 people in the region hit by the quake who have California Earthquake Authority insurance policies to contact their residential insurance agencies as soon as possible. Information on how to file a policy claim is on the agency’s website: EarthquakeAuthority.com, he said.

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Rodriguez reported from San Francisco. Associated Press writer Rachel Lerman in San Francisco and AP Radio reporter Shelly Adler in Washington, D.C., contributed.