CALIFORNIA   -    Emergency officials in southern California’s high desert are braced for strong, potentially dangerous aftershocks from a major earthquake that damaged buildings, ruptured gas lines and sparked numerous fires near its remote epicenter.

The magnitude 7.1 tremor rocked the Mojave desert town of Ridgecrest near Death Valley National Park as darkness fell on Friday, jolting the area with eight times more force than a 6.4 quake that had struck the same area 34 hours earlier. California’s governor, Gavin Newsom, requested federal assistance and placed the state Office of Emergency Services (OES) on its highest alert.

“We have significant reports of fires, structural fires, mostly as a result of gas leaks or gas line breaks,” OES director Mark Ghilarducci told a late-night news conference. The quake also caused water main breaks and knocked out power and communications to parts of Ridgecrest, a city of about 27,000 about 125 miles north-east of Los Angeles.

No fatalities or serious injuries were reported from either quake, police said. But Ghilarducci said the full extent of damage would not be known before daybreak on Saturday.

“This was a very large earthquake, and we also know there’s going to be a series of aftershocks as a result of the main quake,” he said, adding his agency faced a “challenge” getting needed resources to the isolated quake zone.

“This is not going to be something that’s going to be over right away.”

Ridgecrest, where residents were still recovering from Thursday’s quake, again took the brunt of the damage. Megan Person, director of communications for the Kern county fire department, said the county had opened an emergency shelter. A rockslide closed state route 178 in Kern River Canyon, where photos from witnesses also showed that a stretch of roadway had sunk. San Bernardino county firefighters reported cracked buildings and one minor injury. In downtown Los Angeles, 150 miles away, offices in skyscrapers rolled and rocked for at least 30 seconds. Reports said the quake rocked chandeliers and rattled furniture as far away as Las Vegas, and the US Geological Survey said it was felt in Mexico as well. Lucy Jones, a seismologist with the California Institute of Technology’s seismology lab, tweeted that the quake was part of the sequence that produced the earlier quake.

Brian Humphrey of the Los Angeles fire department told KNX-AM radio more than 1,000 firefighters were mobilized, but there were no immediate reports of damage or injuries.

The press box at Dodger Stadium lurched for several seconds and fans in the upper deck appeared to be moving toward the exit. Enrique Hernandez of the Dodgers was at bat in the bottom of the fourth when the quake occurred. He stepped out of the batter’s box, but it was not clear if that was because of the quake. Players and staff left the court after the earthquake was felt during an NBA summer league game between the New York Knicks and the New Orleans Pelicans in Las Vegas.

Friday’s quake came as communities in the Mojave were assessing damage after several fires and multiple injuries caused by Thursday’s quake. A shelter drew 28 people overnight, but “some people slept outside in tents because they were so nervous”, said Marium Mohiuddin of the American Red Cross.

Thursday’s quake opened three cracks across a short stretch of state route 178 near the tiny town of Trona, said California transportation spokeswoman Christine Knadler. Bridges in the area were also being checked.

The pair of quakes were the most powerfulto strike the region since 1994, when the 6.7 magnitude Northridge quake hit the heavily populated San Fernando Valley. That event caused 57 deaths and billions in dollars of damages from collapsed buildings and destroyed freeways.

Southern California residents should expect more earthquakes in coming years, experts warned. “This is the first magnitude 6 quake in 20 years. It’s the longest interval we’ve ever had,” Jones told the Guardian. “We know that the last 20 years was abnormal ... we should expect more earthquakes than we’ve been having recently.” She added: “Chances are, we’re going to have more earthquakes in the next five years than we’ve had in the last five years.”

Los Angeles on Friday revealed plans to lower slightly the threshold for public alerts from its earthquake early warning app. The technology 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 the US Geological Survey’s 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 test users including emergency agencies, industries, transportation systems and schools.

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 the 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. Volunteers assist with cleanup at the Ridgecrest, California, branch of the Kern County Library following the California earthquake.

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 under way, 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.

California is partnering with the federal government to build the system, with the goal of turning it on by June 2021. The state has already spent at least $25m building it, including installing hundreds of seismic stations throughout the state.AGENCIES

CALIFORNIA

Emergency officials in southern California’s high desert are braced for strong, potentially dangerous aftershocks from a major earthquake that damaged buildings, ruptured gas lines and sparked numerous fires near its remote epicenter.

The magnitude 7.1 tremor rocked the Mojave desert town of Ridgecrest near Death Valley National Park as darkness fell on Friday, jolting the area with eight times more force than a 6.4 quake that had struck the same area 34 hours earlier. California’s governor, Gavin Newsom, requested federal assistance and placed the state Office of Emergency Services (OES) on its highest alert.

“We have significant reports of fires, structural fires, mostly as a result of gas leaks or gas line breaks,” OES director Mark Ghilarducci told a late-night news conference. The quake also caused water main breaks and knocked out power and communications to parts of Ridgecrest, a city of about 27,000 about 125 miles north-east of Los Angeles.

No fatalities or serious injuries were reported from either quake, police said. But Ghilarducci said the full extent of damage would not be known before daybreak on Saturday.

“This was a very large earthquake, and we also know there’s going to be a series of aftershocks as a result of the main quake,” he said, adding his agency faced a “challenge” getting needed resources to the isolated quake zone.

“This is not going to be something that’s going to be over right away.”

Ridgecrest, where residents were still recovering from Thursday’s quake, again took the brunt of the damage. Megan Person, director of communications for the Kern county fire department, said the county had opened an emergency shelter. A rockslide closed state route 178 in Kern River Canyon, where photos from witnesses also showed that a stretch of roadway had sunk. San Bernardino county firefighters reported cracked buildings and one minor injury. In downtown Los Angeles, 150 miles away, offices in skyscrapers rolled and rocked for at least 30 seconds. Reports said the quake rocked chandeliers and rattled furniture as far away as Las Vegas, and the US Geological Survey said it was felt in Mexico as well. Lucy Jones, a seismologist with the California Institute of Technology’s seismology lab, tweeted that the quake was part of the sequence that produced the earlier quake.

Brian Humphrey of the Los Angeles fire department told KNX-AM radio more than 1,000 firefighters were mobilized, but there were no immediate reports of damage or injuries.

The press box at Dodger Stadium lurched for several seconds and fans in the upper deck appeared to be moving toward the exit. Enrique Hernandez of the Dodgers was at bat in the bottom of the fourth when the quake occurred. He stepped out of the batter’s box, but it was not clear if that was because of the quake. Players and staff left the court after the earthquake was felt during an NBA summer league game between the New York Knicks and the New Orleans Pelicans in Las Vegas.

Friday’s quake came as communities in the Mojave were assessing damage after several fires and multiple injuries caused by Thursday’s quake. A shelter drew 28 people overnight, but “some people slept outside in tents because they were so nervous”, said Marium Mohiuddin of the American Red Cross.

Thursday’s quake opened three cracks across a short stretch of state route 178 near the tiny town of Trona, said California transportation spokeswoman Christine Knadler. Bridges in the area were also being checked.

The pair of quakes were the most powerfulto strike the region since 1994, when the 6.7 magnitude Northridge quake hit the heavily populated San Fernando Valley. That event caused 57 deaths and billions in dollars of damages from collapsed buildings and destroyed freeways.

Southern California residents should expect more earthquakes in coming years, experts warned. “This is the first magnitude 6 quake in 20 years. It’s the longest interval we’ve ever had,” Jones told the Guardian. “We know that the last 20 years was abnormal ... we should expect more earthquakes than we’ve been having recently.” She added: “Chances are, we’re going to have more earthquakes in the next five years than we’ve had in the last five years.”

Los Angeles on Friday revealed plans to lower slightly the threshold for public alerts from its earthquake early warning app. The technology 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 the US Geological Survey’s 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 test users including emergency agencies, industries, transportation systems and schools.

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 the 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. Volunteers assist with cleanup at the Ridgecrest, California, branch of the Kern County Library following the California earthquake.

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 under way, 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.

California is partnering with the federal government to build the system, with the goal of turning it on by June 2021. The state has already spent at least $25m building it, including installing hundreds of seismic stations throughout the state.