RIDGECREST, California — The magnitude 6.4 earthquake that struck an area of California between Los Angeles and Las Vegas on Thursday morning was the strongest quake to hit the region in 20 years.

The rolling temblor sent dozens aftershocks through the Fourth of July holiday and researchers say they could last for a week. A California official says some injuries and two house fires have been reported in a town near the epicenter.

The United States Geological Survey says on its website that their forecast over the next week includes a 9% chance of one or more aftershocks larger than the Thursday earthquake's magnitude 6.4. It is likely that there will be smaller earthquakes over the next week, with 50 to 700 magnitude 3 or higher aftershocks.

It happened near Searles Valley, California, about 125 miles northeast of Los Angeles and 125 miles west of Las Vegas. The 28,000 residents of Ridgecrest make up the biggest population concentration closest to the epicenter. The quake had a depth of 5.4 miles.

Kern County Fire Chief David Witt also told The Associated Press that emergency crews were dealing with small vegetation fires, cracks on some roads and gas leaks that were reported after the quake in the Mojave Desert.

The U.S.G.S. says magnitude 3 and above are large enough to be felt near the epicenter, and that the number of aftershocks will drop off over time. However, a large aftershock can increase the numbers again, temporarily.

The survey tweeted that at around 1:15 p.m. local time, nearly three hours after the mainshock, there were more than 100 aftershocks at least magnitude 2.5. It also said that hours later there had been over 22 that were strong enough to feel.

It was felt in neighboring states and was followed by dozens of aftershocks. Firefighters nearby reported responding to medical emergencies and fires.

Veteran seismologist Lucy Jones says the earthquake Thursday was the strongest to hit Southern California in 20 years.

She says the previous large quake was a 7.1 that struck in the area on October 16, 1999.

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

In Ridgecrest, Kern County fire officials reported responding to at least two dozen incidents ranging from medical assistance to structure fires.

People as far away as Phoenix -- nearly 350 miles away -- reported feeling it.

RELATED: Prepare to be on your own in a major disaster

A common feature of this quake people had reported was that it lasted a long time.

"The strange thing about this one is it kept rolling and rolling and rolling. It felt like it lasted a good minute," said NBC Nightly News anchor Lester Holt in a phone interview from Los Angeles.

"Bigger quakes last for a longer time. The fault was producing energy for about 5 seconds. What you feel is that plus reverberations," Jones tweeted.

An interactive map from the U.S. Geological Survey showed there were two quakes -- magnitude 2.5 and 4.0 -- in the same area within a half-hour prior to the larger one.

People jumped onto social media to talk about the experience, and President Donald Trump tweeted that he has been briefed on the situation.

Filmmaker Ava DuVernay said she's lived in Los Angeles her entire life and it was the longest earthquake she ever felt.

"Not jerky. Smooth and rolling. But it was loooong. It was so long I thought for the first time ever “Is this the big one?” Damn. Respect Mother Nature. She’s the boss," DuVernay tweeted.

Sports talk show host Colin Cowherd was in the middle of his show on FS1, based in Los Angles, and narrated what he was feeling.

In Las Vegas, some people described it as minor while others experienced more shaking. </s> SAN FRANCISCO (AP) — A large earthquake has rattled a large swath of Southern California. There are no immediate reports of damage.

The quake measured with a preliminary magnitude of 6.6 struck Wednesday morning near the town of Ridgecrest, California, about 150 miles (240 kilometers) northeast of Los Angeles.

People from the desert to the Pacific coast in Southern California reported feeling it. </s> RIDGECREST, Calif. -- A magnitude 5.4 earthquake hit near Searles Valley Friday morning, one day after a powerful 6.4 quake hit the region The quake is one in a series of aftershocks to hit the area since Thursday's 6.4 earthquake. It struck at approximately 4:07 a.m. local time and was centered about 9.7 miles from west of Searles Valley and 10.8 miles north-northeast of Ridgecrest, according to the U.S. Geological Survey.There were no immediate reports of damage in the surrounding area. People felt the quake in various parts of Los Angeles and Orange counties.About an hour and a half after the Friday quake, Los Angeles Fire Department tweeted that it had completed earthquake mode and gone back to normal operations.Thursday's earthquake was the strongest earthquake in the Southern California region since 1999, with people throughout Southern California reported feeling it. Minor cracks, multiple water mains ruptured and several power lines were down after the quake hit, according to the San Bernardino County Fire Department.Firefighters in Kern County responded to nearly two dozen incidents including medical emergencies and reports of a burning home.Kern County Fire Chief David Witt said emergency responders also contended with small vegetation fires, gas leaks and reports of cracked roadways in Ridgecrest, a city with a population of 28,000. Twenty patients were evacuated from Ridgecrest Regional Hospital as a precaution amid a slew of aftershocks, nine of which were measured at magnitude 4.0 or above. </s> Californians woke early Friday to a 5.4-magnitude aftershock, renewing fears one day after Southern California experienced its strongest earthquake in two decades.

Susan Hough, a seismologist with the United States Geological Survey, said the 4:07 a.m. tremor, nine miles northeast of the Mojave Desert city of Ridgecrest near where Thursday’s earthquake took place, would likely be the strongest aftershock, although more powerful ones could follow. There have been about 200 aftershocks since the 6.4-magnitude earthquake on Thursday morning, which led to about two dozen fire and emergency medical calls but no serious injuries.

Thursday’s earthquake punctured a period of relative seismic calm in California, but scientists said it did not change their calculations of when the Big One might strike.

Although the faults around Ridgecrest are part of the larger San Andreas system that runs from the Gulf of California to Mendocino, north of San Francisco, Thursday’s earthquake did not relieve the stress on the San Andreas, said Paul Caruso, a geophysicist with the U.S.G.S. in Golden, Colo. </s> Southern California is earthquake country. But if you’ve lived in the area for the last couple of decades, you might not know it.

Despite Thursday’s wake-up call 6.4 magnitude in a remote desert area near the town of Ridgecrest, Southern California has been experiencing an earthquake drought, scientists said Thursday.

The relative inactivity did not go unnoticed by one high-profile expert on California’s shakers.

“I think this would be a good time to remind you that if you have been experiencing earthquakes for the last 20 years in California, you have been experiencing an extremely quiet time in California history,” Caltech scientist Lucy Jones said.

Take note of that history:

The last time there was an earthquake above magnitude 6 in Southern California was 1999, Jones said.

The previous decade leading up to that had about eight magnitude 6s.

“This has been an extremely quiet, abnormal time,” she said.

Jones said the quake that shook the region on Thursday was actually more “normal” for what we should be expecting in Southern California, based on historical averages.

A quake of the Ridgecrest size, based on long-term history, should be coming once every five or 10 years in Southern California.

Yet, you’d have to go back to Oct. 16, 1999, for anything bigger. That’s when a magnitude 7.1 quake hit about 32 miles north of Joshua Tree.

Until Thursday’s Ridgecrest quake, it was the largest tremor to have hit the area since the 7.3-magnitude Landers Earthquake struck on June 28, 1992. And just this year, the 25th anniversary of the 6.7-magnitude Northridge Earthquake was remembered, along with its tragic toll of 57 people killed.

Here’s a quick rundown on some others above 4.0 over the last 25 years:
• 6.4 magnitude earthquake in Southern California shakes social media with surprise reactions and videos
• LA has an earthquake warning system. It didn’t send an alert for the July 4th quake. So what does this all mean? Are we due? Is there energy building up on the faults throughout Southern California?

It may just come down to being aware.

Here’s what U.S. Geological Survey seismologist Robert Graves had to say about that: “Obviously any earthquake that occurs releases some of that tension. But there’s a tremendous amount that’s built up since the last major earthquake, which was in 1857 on the San Andreas.” </s> LOS ANGELES — A magnitude 6-4 earthquake was felt throughout the Southland Thursday, shaking up local residents celebrating the Fourth of July.

The quake, which began at 10:33 a.m., was centered about 7 miles southwest of Searles Valley, a sparsely populated part of the Mojave Desert near Kern County and northwestern San Bernardino County, according to the U.S. Geological Survey.

Governor Gavin Newsom on Thursday issued an emergency proclamation due to the effects of the earthquake near Ridgecrest in Kern County and continued aftershocks that have damaged infrastructure, homes and other structures and caused fires.

RELATED: Where was the ShakeAlert?

Southland police and fire agencies quickly took to social media, reporting no injuries from the shaking, but some possible damage and one structure fire.

The Los Angeles Department of Water and Power reported a water main break on Wilshire Boulevard and La Jolla Avenue, power outages affecting the Garment District downtown, a portion of San Pedro, and 20 customers in Granada Hills -- though officials later said power was restored in Granada Hills, and the water main break downtown might have been unrelated to the earthquake.

The Los Angeles Fire Department reported shortly after noon that a survey all 106 fire stations "found no signs of any significant damage in the City of Los Angeles nor any injuries."

RELATED: San Diegans sound off on social media about magnitude 6.4 earthquake

The Los Angeles Police Department reported that they have not received any reports of damage or calls for service within the city in relation to the earthquake.

Los Angeles Mayor Eric Garcetti said at 1:30 p.m. that the city was "in great shape," with no significant damage to report.

Officials at LAX said all runways were inspected and no damage was found.

Ride operations were briefly suspended at Six Flags Magic Mountain and Hurricane Harbor in Santa Clarita, but the theme parks tweeted shortly after the quake that operations had resumed as normal.

This photo shows damage on Highway 178 in Ridgecrest, Calif., following an earthquake in the area Thursday, July 4, 2019. The earthquake shook a large swath of Southern California and parts of Nevada on Thursday, rattling nerves on the July 4th holiday and causing some injuries and damage in the town near the epicenter, followed by a swarm of ongoing aftershocks. (AP Photo/Matt Hartman)

Southland police agencies were reminding the public not to use 911 for earthquake questions unless they have injuries or dangerous conditions to report.

The Los Angeles County Fire Department was sending a battalion chief and a task force to Ridgecrest, near Bakersfield, to assist the Kern County Fire Department in earthquake recovery efforts.

Officials with the San Bernardino County Fire Department tweeted that they were conducting an assessment of the region and "no injuries reported, however buildings and roads have sustained varying degrees of damage."

A later tweet said multiple buildings had been found with minor cracks, along with broken water mains, downed power lines and rockslides on certain roads.

The Kern County Fire Department announced that it was responding to nearly two dozen incidents ranging from medical assistance to structure fires in and around the city of Ridgecrest, a town of about 28,000 people and the closest major population center to the epicenter was Ridgecrest.

A state of emergency was later declared in Ridgecrest and signed by Gov. Gavin Newsom, and 15 emergency-room patients were transferred to Palmdale Regional Medical Center while Ridgecrest Regional Hospital was being evaluated for structural damage.

A photo made the rounds on Twitter showing a large crack on Highway 178 near the small town of Trona. Caltrans officials reported Thursday afternoon that the crask "was repaired within one hour by Caltrans District 9 Maintenance crews."

Officials with SoCalGas said an initial inspection revealed "no significant impacts to the natural gas system." The epicenter is within the utility's service area.

It was the strongest quake to be felt in Southern California since 1999, according to seismologist Lucy Jones of Caltech, founder of the Dr. Lucy Jones Center for Science & Society.

Jones said the quake was not on the San Andreas fault.

"It is an area with a lot of little faults but no long fault," she tweeted.

Jones said the "shake alert" computer system at Caltech's seismic facility registered a 48-second warning that shaking had begun, but the warning signal did not go out to the public.

Los Angeles officials later explained that, tweeting: "The #ShakeAlertLA app only sends alerts if shaking is 5.0+ in LA County. Epicenter was 6.4 in Kern County, ??@USGS?? confirms LA*s shaking was below 4.5. We hear you and will lower the alert threshold with ??@USGS_ShakeAlert??"

"Let's remind ourselves that this is not a physical science question," Jones explained. "Giving more alerts convinces people that the system works and generates trust in it. Lots of false alarms generates distrust. Part of the concern in our current early system without complete funding (is) how many false alarms would we be issuing?

" ... The other problem is that there's a lot of use to the alerts beyond damage. Nobody in Los Angeles County was damaged -- nowhere close. We just all felt it. That does not stop people from being scared from feeling it, and one of the questions is what is the psychological benefit of getting a few seconds of warning and knowing that it's coming? That's a hard thing to measure physically."

A magnitude 4.2 quake that preceded the main quake by about 30 minutes was a "foreshock," Jones said.

Several aftershocks in the magnitude-3 range were reported by the USGS, as expected following a substantial quake. Jones said there was a better than 50-percent chance of a larger aftershock in the magnitude-5 area "sometime this afternoon."

The USGS tweeted that "According to our forecast, over the next 1 Week there is a 9% chance of one or more aftershocks that are larger than magnitude 6.4. It is likely that there will be smaller earthquakes over the next 1 Week, with 50 to 700 magnitude 3 or higher aftershocks."

The last Southern California earthquake to exceed 6.4 was on Oct. 16, 1999, when a magnitude 7.1 quake struck in the Mojave Desert near Twentynine Palms Marine Corps Base. That quake knocked an Amtrak passenger train off its tracks and damaged two highway bridges.

The full text of the emergency proclamation is below:



PROCLAMATION OF A STATE OF EMERGENCY

WHEREAS on July 4, 2019, a magnitude 6.4 earthquake centered near the City of Ridgecrest in Kern County caused significant damage; and

WHEREAS multiple earthquake aftershocks continue to impact the region; and

WHEREAS the earthquake damaged roads and buildings, resulted in multiple structural fires, and necessitated evacuations; and

WHEREAS the earthquake damaged critical infrastructure, including electrical service lines, water lines, and gas lines, impacting thousands of customers; and

WHEREAS under the provisions of Government Code section 8558(b), I find that conditions of extreme peril to the safety of persons and property exist in Kern County due to the earthquake; and

WHEREAS under the provisions of Government Code section 8558(b), I find that the conditions caused by the earthquake, by reason of its magnitude, are or are likely to be beyond the control of the services, personnel, equipment, and facilities of any single local government and require the combined forces of a mutual aid region or regions to appropriately respond. </s> LOS ANGELES (AP) — A strong earthquake rattled a large swath of Southern California and parts of Nevada on Thursday morning, making hanging lamps sway and photo frames on walls shake. There were no immediate reports of damage or injuries but a swarm of aftershocks were reported.

The 6.4 magnitude quake struck at 10:33 a.m. in the Mojave Desert, about 150 miles (240 kilometers) northeast of Los Angeles, near the town of Ridgecrest, California. It is the strongest quake to hit the region in 20 years.

The United State Geological Survey initially said it measured at a 6.6 magnitude.

"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.

Veteran seismologist Lucy Jones said the earthquake Thursday was the strongest to hit Southern California in 20 years.

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

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

She says it was 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.

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.'

"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."

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

The quote in the story from Ashleigh Chandler has been corrected to say stepson, not sister. </s> 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.

He said 15 patients were evacuated from the Ridgecrest Regional Hospital as a precaution.

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.

Gov. Gavin Newsom declared a state of emergency for Kern County. The declaration means that the state will help the county and municipalities in it with emergency aid and recovery efforts.

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.

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. </s> SAN FRANCISCO (AP) — An earthquake rattled a large swath of Southern California and parts of Nevada on Thursday morning, making hanging lamps sway and photo frames on wall shake. There were no immediate reports of damage or injuries.

The 6.4 magnitude quake measured struck near in the Mojave Desert, about 150 miles (240 kilometers) northeast of Los Angeles, near the town of Ridgecrest, California.

The United State Geological Survey initially said it measured at a 6.6 magnitude.

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.

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.'

"My sister 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."
An earthquake with a magnitude of 6.4 with scores of foreshocks and aftershocks hits Southern California, 150 miles (240 km) north of Los Angeles near the city of Ridgecrest. No injuries are reported. The earthquake is the largest in Southern California since October 1999.