PLANETARY TREMORS: Powerful 5.1 Magnitude Earthquake Strikes California, 20 Miles Southeast Of Los Angeles – Over 100 Aftershocks; Scattered Damage; Residents Flee From Homes; USGS Says It Could Be A Foreshock Of Larger Temblor In The Next Few Hours Or Days! [PHOTOS+MAPS]

March 29, 2014 – CALIFORNIA, UNITED STATES –  Authorities were tallying damage from a magnitude 5.1 earthquake that struck Southern California Friday evening.

More than 100 aftershocks have been reported since a magnitude 5.1 earthquake rattled Southern California on Friday night. Most of the afteshocks have been small, but some were strong enough to be felt in the areas around the epicenter in northwestern Orange County.

USGS earthquake location map.

Fullerton police said early Saturday that up to 50 people had been displaced because of home damage.

The quake, centered near La Habra, caused furniture to tumble, pictures to fall off walls and glass to break. Merchandise fell off store shelves, and there were reports of plate glass windows shattered.

In Brea, several people suffered minor injuries during a rockslide that overturned their car. Fullerton reported seven water main breaks. Carbon Canyon Road was closed.

USGS earthquake shakemap intensity.

Residents across Orange and Los Angeles counties and the Inland Empire reported swinging chandeliers, fireplaces dislodging from walls and lots of rattled nerves. The shake caused a rock slide in Carbon Canyon, causing a car to overturn, according to the Brea Police Department. Fullerton police received reports of water main breaks and windows shattering, but primarily had residents calling about burglar alarms being set off by the quake.

Third-grade teacher Barbara Castillo and her 7-year-old son had just calmed their nerves after the first temblor and sat down in their La Habra home when their dogs started barking and the second, larger quake struck, causing cabinet doors to swing open, objects to fall off shelves and lights to flicker.

“It just would not stop, it was like an eternity,” said Castillo, an 18-year La Habra resident.

At Disneyland in Anaheim, all rides were halted as a precaution but no damage or injuries were reported — other than ceiling tiles falling in the police station, Sgt. Daron Wyatt said.

The first of a swarm of earthquakes hit the border of La Habra and Brea shortly after 8 p.m. with a 3.6 temblor. About an hour later, at 9:09 p.m., a 5.1 shock hit, followed by at least two more aftershocks in the 3-point range in the next half hour. At least 20 aftershocks had been recorded by late Friday.

Damage at the 99 Cent Store on Imperial Highway in Brea.
( Robert Gauthier, Los Angeles Times / March 28, 2014 )

Fullerton police stand by as a city employee fixes a water main break at the intersection of Gilbert St. and Rosecrans Ave.
( Allen J. Schaben, Los Angeles Times / March 28, 2014 )

Cesar Zamora, night manager at the 99 Cent Only store on Imperial Highway, looks over aisles of fallen goods.
( Robert Gauthier, Los Angeles Times / March 28, 2014 )

A BMW is damaged from a rock slide in Carbon Canyon after a 5.1 earthquake. The road was closed because
of the risk of an aftershock. ( Francine Orr / Los Angeles Times / March 28, 2014 )

Shampoo and soap containers are strewn about in the 99 Cent Only store on Imperial Highway.
( Robert Gauthier, Los Angeles Times / March 28, 2014 )

Richard Rodriguez, left, and Guillermo Valencia board up a broken window at Towne Cleaners in La Habra, the
epicenter of Friday’s 5.1 earthquake. ( Allen J. Schaben, Los Angeles Times / March 29, 2014 )

U.S. Geological Survey seismologist Lucy Jones said the 5.1 quake has a 5% chance of being a foreshock of a larger temblor.

“There could be even a larger earthquake in the next few hours or the next few days,” Jones said during a media briefing at Caltech.

Experts said that based on preliminary data, the series of earthquakes appeared to have occurred on the Puente Hills thrust fault, which stretches from the San Gabriel Valley to downtown Los Angeles. The fault also caused the 1987 Whittier Narrows earthquake.

Friday night’s 5.1 quake was relatively shallow, which “means the shaking is very concentrated in a small area,” said Caltech seismologist Egill Hauksson. Hauksson said the quake sequence was unusual in that the 5.1 quake was preceded about an hour earlier by a weaker foreshock.

Scientists are particularly concerned about the Puente Hills thrust fault because it goes directly underneath downtown Los Angeles. “This is the fault that could eat L.A.,” seismologist Sue Hough told The Times in 2003.

On Friday, though, police and fire departments in Los Angeles reported no damage. “Tonight’s earthquake is the second in two weeks, and reminds us to be prepared,” Los Angeles Mayor Eric Garcetti said in a statement.

Although the shaking was felt throughout the region, it didn’t rattle the professionalism at Walt Disney Concert Hall. Microphones above the stage swung back and forth and the hall shook, but the orchestra continued playing.

“The L.A. Philharmonic should get combat pay,” said audience member Michael Healy of Studio City. – LA Times.

Tectonic Summary

A M5.1 earthquake occurred at 9:09PM on March 28, 2014, located 1 mile easy of La Habra, CA, or 4 miles north of Fullerton, CA. The event was felt widely throughout Orange, Los Angeles, Ventura, Riverside, and San Bernardino counties.  It was preceded by two foreshocks, the larger of M3.6 at 8:03pm.  The demonstration earthquake early warning system provided 4 second warning in Pasadena. 

There have been 23 aftershocks as of 10:00PM on March 28, the largest of which was a M3.6 at 9:30PM, and was felt locally near the epicenter. The aftershock sequence may continue for several days to weeks, but will likely decay in frequency and magnitude as time goes by.

The maximum observed instrumental intensity was VII, recorded in the LA Habra and Brea areas, although the ShakeMap shows a wide area of maximum intensity of VI. The maximum reported intensity for the Did You Feel It? map was reported at VI in the epicentral area.

This sequence could be associated with the Puente Hills thrust (PHT).  The PHT is a blind thrust fault that extends from this region to the north and west towards the City of Los Angeles.  It caused the M5.9 1987 Oct. 1 Whittier Narrows earthquake. 

Previously, the M5.4 2008 Chino Hills earthquake occurred in this region.  It caused somewhat stronger shaking in Orange County and across the Los Angeles Basin. 

The moment tensor shows oblique faulting, with a north dipping plane that approximately aligns with the Puente Hills thrust. – USGS.

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