
The 7.1 magnitude earthquake that sparked huge fires and caused multiple injuries in Southern California on Friday evening was 11 times stronger than the 6.4 tremor in the same region just 32 hours earlier, geologists say.

Shockwaves from Friday's quake were felt in Las Vegas and downtown Los Angeles as a rolling motion that seemed to last at least a half-minute.

Dr Lucy Jones, a seismologist for the California Institute of Technology (CalTech), said it was the most powerful to hit Southern California since another 7.1 temblor in the same area in 1999.

Jones also warned there is about a one-in-10 chance that another 7.0 quake could hit within the next week, and the the chance of a 5.0-magnitude quake 'is approaching certainty'.

There have already been more than 1,700 aftershocks recorded since Thursday's quake, which is being considered a 'foreshock' to Friday's 'mainshock'.

Compared to the first shock, the second was 11 times stronger, five times bigger and lasted longer.

The strength of the earthquake is the most important measure, referring to the amount of energy released and thus the amount of damage. Friday's quake released 11 times the amount of energy of Thursday's, while it measured five times larger on the seismograph.

'It is really the energy or strength that knocks down buildings,' according to the US Geological Survey (USGS).

Aftershocks from the mainshock could occur for years, Jones said. Seismologists have predicted that there is an 11 percent chance of a magnitude 7 or greater temblor hitting Southern California in the next week, with an eight to nine percent chance that it will be higher than Friday's.

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A powerful 7.1 magnitude earthquake struck Southern California on Friday night, just one day after the region was rocked by a 6.4 magnitude earthquake. A firefighter is seen battling flames from an electrical fire at a mobile home park in Ridgecrest

Emergency rescue crews fanned out Saturday to assess damage in Ridgecrest from the second powerful earthquake

No fatalities or serious injuries have been reported from this second quake, the largest in Southern California in 20 years

An employee walks past broken bottles scattered on the floor in Eastridge Market in Ridgecrest on Saturday morning

Food is seen strewn across the floor at a Walmart in Yucca Valley, California, after the earthquake hit Friday night

Smoke billows from a fire that broke out behind the Casa Corona restaurant following an earthquake in Ridgecrest on Friday

The fire may have been caused by a gas leak, a frequent phenomenon during earthquakes. Local fire and police officials said they were initially swamped by calls for medical and ambulance service but the damage wasn't too extensive

Two news anchors for the local CBS affiliate in Los Angeles - Juan Fernandez and Sara Donchey - were filmed live on the air as the earthquake hit, sending them into a panic

WATCH: @CBSLA anchors seek shelter under desk during live broadcast when 6.9 magnitude Southern California earthquake strikes pic.twitter.com/hB7wyWulQD — Evan Rosenfeld (@Evan_Rosenfeld) July 6, 2019

Highway workers repair a massive crack in the road that opened outside Ridgecrest following Friday's quake

The map above shows the region in Southern California impacted by the earthquakes on Thursday and Friday

AFTERSHOCK FORECAST The likelihood that Southern California will experience another earthquake of magnitude 7 or greater in the next week is now nearly 11 percent, seismologists say. The odds that a temblor will surpass the 7.1 quake that struck outside Ridgecrest Friday night are between eight and nine percent, Caltech seismologist Lucy Jones said. The US Geological Survey calculated the following odds for the next week by magnitude: Magnitude 3 or higher: greater than 99 percent 'It is most likely that as few as 360 or as many as 660 such earthquakes may occur in the case that the sequence is re-invigorated by a larger aftershock.' Magnitude 5 or higher: greater than 99 percent 'It is most likely that as few as zero or as many as 11 such earthquakes may occur. Magnitude 6 or higher: 39 percent 'It is most likely that as few as zero or as many as three such earthquakes may occur.' Magnitude 7 or higher: 5 percent 'Such an earthquake is possible but with a low probability.' AFTERSHOCKS EXPLAINED Aftershocks are smaller earthquakes that occur in the same general area during the days to years following a larger event or 'mainshock', according to USGS. As a general rule, aftershocks represent minor readjustments along the portion of a fault that slipped at the time of the mainshock. The frequency of aftershocks decreases sharply in the first ten days after the quake. Bigger earthquakes have more and larger aftershocks. The bigger the mainshock, the bigger the largest aftershock, on average, though there are many more small aftershocks than large ones. Also, just as smaller earthquakes can continue to occur a year or more after a mainshock, there is still a chance for a large aftershock long after an earthquake. Advertisement

The Friday magnitude 7.1 earthquake hit about 11 miles from Ridgecrest, the town in Kern County which was very close to the epicenter of the magnitude 6.4 quake felt on Thursday.

The larger tremor was felt as far north as Sacramento, as far east as Las Vegas and as far south as Mexico.

During a press conference Saturday morning, Kern County Fire Chief David Witt said there are no known fatalities from the earthquake but admitted that little is known about the destruction at this point.

'We do feel like there is damage, but we don’t know the extent of it yet,' Witt told reporters. 'Nobody was trapped, no major collapses that we know of, but we are out there searching.'

He said damage evaluation is just picking up speed because 'it's hard to gather intel in darkness'.

Firefighters were seen battling flames at a mobile home park in Ridgecrest overnight after an electrical fire broke out.

Some 3,000 people in the town were left without power and there were reports of cracked buildings.

Two building fires - one involving a mobile home - were quickly doused, and there were several reports of natural gas leaks, but the lines were shut off, McLaughlin said.

For the second time in as many days, Ridgecrest Regional Hospital wheeled patients out of the building, some still hooked to IVs, CNN reported.

Several residents removed their mattresses from their homes and slept outside on Friday night because they felt it was safer than being inside.

'When you lose all ability and sense of — sort of your own control of your surroundings, it is scary,' CNN's Sara Sidner said after interviewing Ridgecrest residents.

'When the Earth is literally moving underneath you and things are falling off the walls and you don't know how much longer it's going to go on, it feels like eternity as one of these earthquakes roll through."

Nearby, the tiny town of Trona, with about 2,000 residents, was reported to have at least one collapsed building. Roads were buckled or blocked, and police put out a call for bottled water for residents.

State Route 178 in Kern County was closed by a rockslide and had severe cracking. Fire officials reported 'multiple injuries and multiple fires' without providing details.

San Bernardino County firefighters reported cracked buildings and a minor injury.

'Homes shifted, foundation cracks, retaining walls down,' the department said on Twitter.

'One injury (minor) with firefighters treating patient. No unmet needs currently.'

The seismograph at left shows the peak of Friday night's 7.1 magnitude earthquake, while the map at right shows the location of aftershocks that have been recorded since the 6.4 magnitude on Thursday

Jenner Kim, 50, surveys the significant damage at his small storage facility in Trona after the July 4 earthquake

In Ridgecrest, some 3,000 people were left without power and there were reports of cracked buildings

An employee stands among the wreckage of a gas station and liquor store in Ridgecrest after the quake hit Friday night

Wine bottles litter the aisles of a liquor store after having been shaken off their shelves in the tremor

In downtown Los Angeles, 150 miles away, offices in skyscrapers rolled and rocked for at least 30 seconds.

The Los Angeles commuter rail service Metrolink said on Twitter it has stopped service in the city of 4 million people for the time being.

Andrew Lippman, who lives in suburban South Pasadena, was sitting outside and reading the paper when Friday's quake hit and calculated it lasted 45 seconds.

California Governor Gavin Newsom activated the Governor's Office of Emergency Services to its highest level on Friday

'I could see power lines swaying,' he said.

Disneyland in Orange County and Six Flags Magic Mountain in Santa Clarita closed their rides.

Juan Fernandez and Sara Donchey, two news anchors for the local CBS affiliate in Los Angeles, were seen live on the air seeking shelter as the quake struck on Friday.

'We are experiencing quite a bit of shaking if you bear with us a moment,' Donchey said.

'We're making sure nothing is going to come down in the studio here.'

A visibly terrified Donchey then grabs Fernandez's arm.

'This is a very strong earthquake,' she said.

'8:21 here and we're experiencing very strong shaking. I think we need to get under the desk Juan.'

Donchey then got under the desk and the station cut to a commercial break.

'We are experiencing quite a bit of shaking if you bear with us a moment,' Donchey said. 'We're making sure nothing is going to come down in the studio here.' A visibly terrified Donchey then grabbed Fernandez's arm (left). Donchey then got under the desk (right) and the station cut to a commercial break

The tremor in Vegas forced the NBA to cancel its nationally televised Summer League game between the New York Knicks and the New Orleans Pelicans.

Television footage from the game at the Thomas and Mack Center in Las Vegas shows the players and coaches walking off the court after tremors were felt throughout the arena.

Images also show the scoreboard and speakers attached to the roof wobbling back and forth as the aftershocks take effect.

The arena was filled to capacity as basketball fans eagerly anticipated the debut of No. 1 overall pick Zion Williamson of the Pelicans.

Williamson and his team were squaring off against another prized Duke product, RJ Barrett, who was picked No. 3 overall by the New York Knicks.

Aftershocks here at Vegas Summer League. Scoreboard and speakers swaying just a bit. pic.twitter.com/HRaddGs6MH — Jeff Zillgitt (@JeffZillgitt) July 6, 2019

Panicked fans are seen above heading for the exits at the Thomas & Mack Center in Las Vegas as tremors are felt in the middle of the NBA Summer League game between the New York Knicks and the New Orleans Pelicans on Friday evening

The NBA announced that it was suspending games on Friday due to the earthquake

Members of the Pelicans, including top draft pick Zion Williamson (right), are seen leaving the court

The scoreboard and the speakers in the arena were visibly shaking as the quake was felt

The New York Knicks wait on the sidelines after the earthquake struck during their game on Friday against the Pelicans in Las Vegas

Players and staff leave the court after the earthquake struck late on Friday

We had an earthquake in LA today and our crew reacted, well, as any one of us would if we were in the middle of an earthquake. pic.twitter.com/dSzTJ4hIeh — FOX Sports: MLB (@MLBONFOX) July 6, 2019

The NBA announced that it postponed the rest of Friday's scheduled Summer League games in Las Vegas because of the earthquake.

The earthquake also rattled Dodger Stadium in the fourth inning of the team's game against the San Diego Padres.

The quake on Friday night happened when Dodgers second baseman Enriquè Hernàndez was batting.

The Los Angeles Dodgers tweeted about the quake that hit as they were hosting the San Diego Padres at Dodger Stadium

It didn't appear to affect him or Padres pitcher Eric Lauer.

However, it was obvious to viewers of the SportsNet LA broadcast when the TV picture bounced up and down.

There was no announcement by the stadium's public address announcer.

The Padres also tweeted about the quake on Friday

Some fans in the upper deck appeared to leave their seats and move to a concourse at the top of the stadium.

The press box lurched for about 20 seconds.

Another local posted video on social media showing the earthquake strike as he was dining at a restaurant in Coachella Valley on Friday.

A resident of Los Angeles posted a video on Twitter showing the earthquake's impact on the swimming pool in her backyard, but social media users were more interested in the fact that her terrified dog was locked out of the house in the middle of the tremors.

A resident of Los Angeles posted a video on Twitter showing the earthquake's impact on the swimming pool in her backyard

But social media users were more interested in the fact that her terrified dog was locked out of the house in the middle of the tremors. Fortunately, the dog, Max, was okay

California Governor Gavin Newsom announced on Friday that he was activating the Governor's Office of Emergency Services to its highest level.

'In response to another large earthquake in Southern California tonight, I have activated the [OES] state operation center to its highest level,' the governor tweeted on Friday.

'The state is coordinating mutual aid to local first responders.'

Communities in the Mojave Desert tallied damage and made emergency repairs to cracked roads and broken pipes earlier on Friday as aftershocks from Thursday's earthquake in Southern California kept rumbling.

The town of Ridgecrest, close to the epicenter, assessed damage after several fires and multiple injuries that were blamed on the magnitude 6.4 quake on Thursday.

Big Bang Theory star Kaley Cuoco shared her reaction to Friday night's earthquake on Instagram Friday night, saying: 'I could hear the alcohol bottles in our bar clanging together.' Her equestrian husband Karl Cook (right) seemed less concerned

A shelter drew 28 people overnight but not all of them slept inside amid the shaking.

'Some people slept outside in tents because they were so nervous,' said Marium Mohiuddin of the American Red Cross.

Damage appeared limited to desert areas, although the quake was felt widely, including in the Los Angeles region 150 miles away.

The largest aftershock thus far - magnitude 5.4 - was also felt in LA before dawn Friday.

The odds of a quake of similar size happening in the next few days continued to dwindle and was only 6 percent on Friday, seismologists said.

There had been about 1,700 aftershocks since the Thursday quake, which was a bit higher than average, said Zachary Ross of the California Institute of Technology.

Locals posted video on Twitter showing the water from swimming pools overflow as a result of the earthquake on Friday

Others on social media kept a sense of humor - with one posting a funny meme about fighting the San Andreas fault (left) and another with a GIF of Homer Simpson predicting that 'the end is near' (right)

Los Angeles International Airport released a statement saying that they had no reports of injuries (left). The Los Angeles Police Department reminded the public of phone numbers to call in case of an emergency (right)

Randi Mayem Singer, a screenwriter, tweeted: 'THAT. WENT. ON. FOREVER.'

A day after a powerful earthquake hit the area, this social media user observed that Mother Nature had other plans for Southern California on Friday

Dozens of people reacted to the earthquake on Twitter. One user joked that he was going back to New York after three earthquakes in a row (left), which another shared a video of the restaurant he was in when the quake hit (right)

'An event of this size is going to keep producing aftershocks for years but the rates are going to decay with time,' Ross said.

The quake involved two perpendicular faults in the area but it was unlikely to affect any fault lines away from the immediate area, seismologists said.

Damage in the town of Ridgecrest was relatively light because the city is relatively young, with growth coming in the 1940s and later so many buildings met upgraded building codes, said Susan Hough of USGS.

Ridgecrest Regional Hospital remained closed as state inspectors assessed it, spokeswoman Jayde Glenn said. The hospital's own review found no structural damage, but there were cracks in walls, broken water pipes and water damage.

The image above taken on Thursday shows hundreds of books which tumbled off the shelves at Kern County Library in Ridgecrest, California after a strong 6.4 magnitude earthquake

A wall at the Esparza Restaurant has several new cracks after an earthquake in Trona. The image above was taken on Friday

Fissures that opened up under a highway during a powerful earthquake that struck Southern California are seen near the city of Ridgecrest on Thursday

People take pictures of a mobile home in Ridgecrest on Friday. The home was knocked off its foundation in the Fourth of July earthquake

Workers repair power lines after they were damaged during an earthquake in Trona

The hospital was prepared to help women in labor and to give triage care to emergency patients.

Fifteen patients were evacuated to other hospitals after the quake, Glenn said.

The quake did not appear to have caused major damage to roads and bridges in the area, but it did open three cracks across a short stretch of State Route 178 near the tiny town of Trona, said California Department of Transportation district spokeswoman Christine Knadler.

Those cracks were temporarily sealed, but engineers were investigating whether the two-lane highway was damaged beneath the cracks, Knadler said. Bridges in the area were also being checked.

The Ridgecrest library was closed as volunteers and staff picked up hundreds of books that fell off shelves.

The building's cinderblock walls also had some cracks, said Charissa Wagner, library branch supervisor.

Wagner was at her home in the small city of 29,000 people when a small foreshock hit, followed by the large one, putting her and her 11-year-old daughter on edge.

'The little one was like, 'Oh what just happened.' The big one came later and that was scarier,' she said.

The earthquake knocked over a boulder that sat atop one of the rock spires at Trona Pinnacles outside of Ridgecrest, a collection of towering rock formations that has been featured in commercials and films, said Martha Maciel, a Bureau of Land Management spokeswoman in California.

Meanwhile, the nation's second-largest city revealed plans to lower slightly the threshold for public alerts from its earthquake early warning app.

But officials said the change was in the works before the quake, which gave scientists at the California Institute of Technology's seismology lab 48 seconds of warning but did not trigger a public notification.

'Our goal is to alert people who might experience potentially damaging shaking, not just feel the shaking,' said Robert de Groot, a spokesman for USGS' ShakeAlert system, which is being developed for California, Oregon and Washington.

The West Coast ShakeAlert system has provided non-public earthquake notifications on a daily basis to many test users, including emergency agencies, industries, transportation systems and schools.

Traffic drives over a patched section of Highway 178 between Ridgecrest and Trona on Friday

Another crack on Highway 178 is seen above as construction crews work to fix a broken water line near Trona on Thursday

Late last year, the city of Los Angeles released a mobile app intended to provide ShakeAlert warnings for users within Los Angeles County.

The trigger threshold for LA's app required a magnitude 5 or greater and an estimate of level 4 on the separate Modified Mercali Intensity scale, the level at which there is potentially damaging shaking.

Although Thursday's quake was well above magnitude 5, the expected shaking for the Los Angeles area was level 3, de Groot said.

A revision of the magnitude threshold down to 4.5 was already underway, but the shaking intensity level would remain at 4. The rationale is to avoid numerous ShakeAlerts for small earthquakes that do not affect people.

'If people get saturated with these messages, it's going to make people not care as much,' he said.

Construction of a network of seismic-monitoring stations for the West Coast is just over half complete, with most coverage in Southern California, San Francisco Bay Area and the Seattle-Tacoma area.

Eventually, the system will send out alerts over the same system used for Amber Alerts to defined areas that are expected to be affected by a quake, de Groot said.

California is partnering with the federal government to build the statewide earthquake warning system, with the goal of turning it on by June 2021.

The state has already spent at least $25million building it, including installing hundreds of seismic stations throughout the state.

This year, Democratic Gov Gavin Newsom said the state needed $16.3million to finish the project, which included money for stations to monitor seismic activity, plus nearly $7million for 'outreach and education.'

The state Legislature approved the funding last month, and Newsom signed it into law.