Earthquakes north of L.A. appear to be on or close to San Andreas, Garlock faults
-
Click here to listen to this article - Share via
See more from the L.A. Times in Google Search. Set us as preferred
Back-to-back earthquakes rocked the area north of Los Angeles near two of California’s most significant faults — including the mighty San Andreas — sending shock waves across the region.
The first quake, a magnitude 4.1, hit at 3:38 a.m. Sunday just outside the unincorporated community of Frazier Park, near the Grapevine section of the 5 Freeway. Weak shaking was felt as far away as Santa Clarita, Palmdale and Bakersfield, according to the U.S. Geological Survey.
It was followed by a magnitude 4.3 that ruptured at 9:40 a.m. Monday, with an epicenter in the Mojave Desert, roughly halfway between the towns of Ridgecrest and California City. Weak shaking was felt as far away as Los Angeles, Victorville and the Santa Clarita, San Fernando and San Gabriel valleys.
The Frazier Park earthquake “was probably on the San Andreas,” said Kate Scharer, a USGS geologist. A magnitude 4.1 earthquake, however, is fairly small, the kind where people might feel “a little wiggle,” she added.
The epicenter of that quake sits at the intersection of the San Andreas and Garlock faults.
“It’s the intersection of the two biggest faults in the state, and there’s a lot of questions of about about how that area actually behaves,” said Julian Lozos, associate professor of geological sciences at Cal State Northridge.
A major California fault capable of producing a magnitude 8 earthquake has begun moving for the first time on record since July’s Ridgecrest quakes.
The southern San Andreas fault, which stretches from Monterey County through Los Angeles County and the Inland Empire to the Salton Sea near the Mexican border, is capable of a catastrophic quake, with some experts theorizing a magnitude 8.2 temblor is possible if the entire stretch ruptures. A powerful earthquake on this roughly 300-mile span would cause the worst shaking the Southern California region has felt since 1857 and send destructive tremors through Los Angeles and beyond.
The 160-mile Garlock fault is less well known, but capable of producing a magnitude 8 earthquake, experts have said. A large quake there has the potential to send strong shaking to the San Fernando Valley, Santa Clarita, Lancaster, Palmdale, Ventura, Oxnard, Bakersfield and Kern County, one of the nation’s most productive regions for agriculture and oil production.
Supershear earthquakes are more common than previously believed, some scientists say — carrying potentially profound risk for communities across California.
The two faults also have the potential to interact with each other — as a major quake on the Garlock fault could destabilize the San Andreas.
Monday’s Mojave Desert quake was just south of the Garlock fault, Lozos said.
The two earthquakes are not unusual for California, and neither was it unusual for people in the L.A. Basin to feel them. The quakes don’t provide any hints of the exact timing or location of the next destructive temblor that will hit urban Southern California.
But the quakes are a reminder to be prepared, and that earthquakes in the Mojave Desert are capable of affecting seismic stress on the San Andreas fault.
“Whenever there’s a bigger earthquake out there, I mean, there’s always a concern of what it’s going to do to nearby faults like the San Andreas,” Lozos said.
New odds mean a large quake on the Garlock fault is much more likely and the chance of a large quake on the San Andreas has also increased.
The recent mild quakes, he said, are “just a good reminder that we are on an active plate boundary with a lot of faults.” Earthquakes with modest magnitudes in the 4.0 range are strong enough that “people are going to notice it and talk about it.”
These two quakes are “probably not big enough to cause a bigger thing, but it’s a sign to check that you’re prepared for when we inevitably do get a bigger thing,” Lozos said.
There’s a 60% chance of a magnitude 6.7 or greater earthquake striking the Los Angeles region by 2045, according to USGS estimates published in 2015.
The largest temblor to hit Southern California in recent memory was the magnitude 7.1 Ridgecrest earthquake, which hit at 8:19 p.m. on July 5, 2019. It caused damage in the town of Ridgecrest and was estimated to have caused billions of dollars in damage to the remote Naval Air Weapons Station China Lake, the Navy’s largest base for developing and testing weapons of warfare.
Did you feel this earthquake? Consider reporting what you felt to the USGS.
More to Read
More From the Los Angeles Times
Podcasts
Kim, an attorney and former San Francisco supervisor, is running against State Sen. Benjamin Allen for the role of running California’s long-beleaguered Department of Insurance. In this episode she talks to Rebuilding L.A. host Kate Cagle about why she should get the job.
The Hillside Strangler murders terrorized Los Angeles in the late 1970s. The killers were a pair of sadistic cousins. One confessed. The other was set to stand trial—until L.A. prosecutors flinched.
Hosts Fidel Martínez and Suzy Exposito sit down with Puerto Rican rapper and composer Álvaro Díaz, fresh off the release of OMAKASE — his third album, a genre-defying concept record that debuted at number one globally on Spotify and is charting in 16 Latin American countries.
