It was the strongest SoCal quake in three years. Here’s why it packed such a punch in L.A.

A magnitude 5.2 earthquake, centered about 18 miles southwest of Bakersfield, was felt throughout a large swath of Southern California on Tuesday evening.

Its dimension rattled nerves however brought about no main harm or accidents. Two minutes after the earthquake hit, a big boulder — the scale of an SUV — was reported blocking a number of southbound lanes of Interstate 5, a couple of mile south of Grapevine Street, the California Freeway Patrol stated. The boulder was cleared by Wednesday morning.

The earthquake, initially estimated at magnitude 5.3, struck at 9:09 p.m., in keeping with the U.S. Geological Survey. It was adopted by dozens of aftershocks of magnitude 2.5 and up, together with a magnitude 4.5 earthquake that occurred lower than a minute after the primary, and a magnitude 4.1 temblor at 9:17 p.m.

The epicenter was in sparsely populated farmland, about 14 miles northwest of the unincorporated neighborhood of Grapevine in Kern County, 60 miles northwest of Santa Clarita, and about 88 miles northwest of downtown Los Angeles.

The world closest to the epicenter felt “very sturdy” shaking as outlined by the Modified Mercalli Depth Scale; that zone features a part of the California Aqueduct, which transports water from Northern California to Southern California.

By the point shaking was felt in additional populated areas, together with Bakersfield, Santa Clarita and Ventura, the USGS calculated that solely “weak” shaking was felt, which might rock standing vehicles and trigger vibrations in a constructing just like the passing of a truck.

Some residents affected by the quake reported an prolonged interval of shaking. One individual in Los Feliz felt 45 seconds of motion, with no less than three completely different waves — one weak, adopted by a robust one, then once more a weak one. In South Pasadena and Whittier, folks felt about 20 seconds of shaking, contained in two distinctive waves.

In Pasadena, seismologist Lucy Jones stated she felt about three seconds of shaking.

There have been no quick studies of harm. And never everybody felt the earthquake. L.A. County Sheriff’s Deputy Jose Gomez stated he didn’t really feel the shaking throughout his drive into work on the sheriff’s Santa Clarita station. No harm was reported there.

The Los Angeles Hearth Division stated no vital harm was reported inside metropolis limits. Preliminary inspections of the State Water Undertaking services, together with the California Aqueduct, discovered no harm.

The USGS stated the quake was felt throughout the Los Angeles Basin and inland valleys and in Santa Maria, Bakersfield and Fresno.

Many Southern California residents described getting alerts from the USGS’ earthquake early warning system, corresponding to via the MyShake app or on their Android telephones. (The earthquake early warning system is robotically put in on Android telephones, however folks with Apple iOS telephones want to put in the MyShake app to get essentially the most well timed alerts.)

One individual described getting 30 to 45 seconds of warning earlier than feeling the shaking arrive. One other individual, in east Anaheim, reported 30 seconds of warning earlier than shaking arrived.

Jones, a analysis affiliate at Caltech, stated the length of shaking can differ a lot within the L.A. space as a result of the size of time the earth strikes at any given spot can depend upon the soil and rocks beneath the placement, whether or not an individual is sitting nonetheless or transferring round, and even whether or not a person is on the bottom ground or on high of a skyscraper — these on larger flooring really feel the shaking extra strongly.

The explanation some folks could have felt a couple of wave of shaking is that the primary aftershock occurred so quickly — lower than a minute — after the primary shock, Jones stated.

Geophysics professor Allen Husker, head of the Southern California Seismic Community at Caltech, stated it wasn’t shocking that so many individuals within the L.A. space felt vital shaking from a magnitude 5.2 earthquake north of the Grapevine. The temblor occurred at evening, when persons are resting and extra more likely to really feel shaking from a distant quake than in the event that they had been out and about in the course of the day and lively.

One more reason many individuals felt substantial motion is because of the manner shaking is amplified within the Los Angeles Basin. The basin is a 6-mile-deep, bathtub-shaped gap within the underlying bedrock stuffed with weak sand and gravel eroded from the mountains and forming the flat land the place tens of millions of individuals stay. It stretches from Beverly Hills via southeast L.A. County and into northern Orange County.

“The basin impact … will increase the shaking that you’d in any other case usually have,” Husker stated.

The impact occurs when waves from the shaking arrive and hit the partitions of the basin, then bounce again on the partitions of the basin, Jones stated, leading to an “prolonged length.”

A significant earthquake on the San Andreas fault would end in maybe 50 seconds of sturdy shaking in downtown L.A. “This earthquake was a lot, a lot smaller, after all,” Jones stated, “however it was giant sufficient to arrange a few of these basin results and get issues bouncing round.”

As with all earthquakes, there was a 1 in 20 likelihood that Tuesday’s temblor was a foreshock to a bigger earthquake. The chance {that a} follow-up quake can be bigger diminishes over time.

It has been a number of years since a magnitude 5.2 or larger earthquake hit Southern California, and Tuesday’s quake was the strongest to strike the area in three years. A magnitude 5.3 quake occurred in June 2021 simply southeast of the Salton Sea in Imperial County, about 160 miles southeast of downtown Los Angeles. And in June 2020, a magnitude 5.5 quake struck the Mojave Desert within the northwestern nook of San Bernardino County, about 120 miles northeast of downtown L.A. and about 14 miles east of Ridgecrest in Kern County.

The earthquake occurred about 12 miles northwest of the epicenter of the magnitude 7.5 Kern County earthquake that struck on July 21, 1952. That earthquake resulted in 12 deaths, and, in keeping with the USGS, previous and poorly constructed masonry buildings suffered harm. A few of these constructions collapsed in communities together with Tehachapi, Bakersfield and Arvin; heavy harm was reported at Kern County Common Hospital.

Shaking from the 1952 earthquake was felt as far-off as San Francisco and Las Vegas, and brought about nonstructural however intensive harm to tall buildings within the Los Angeles space and harm to no less than one constructing in San Diego, in keeping with the USGS.

The 1952 earthquake occurred on the White Wolf fault. Tuesday’s earthquake wasn’t related to any beforehand mapped faults.

Occasions workers writers Jon Healey, Ian James, Jason Neubert, Sandra McDonald and Raul Roa contributed to this report.