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Is 4.4 jolt an end to Los Angeles' 'earthquake drought'?

Seismologists say Monday's magnitude 4.4 temblor near Westwood could mark the beginning of the end for L.A.'s years-long "earthquake drought."

Typically, they would expect a 4.4-sized earthquake about once a year in the Los Angeles Basin, but that hasn't happened for years.

“We don’t know if this is the end of the earthquake drought we’ve had over the last few years, and we won’t know for many months,” said Caltech seismologist Egill Hauksson.

FORESHOCK? What the odds are

The magnitude 4.4 earthquake that struck near Westwood at 6:25 a.m. is the most significant shake in Southern California since a 5.5 earthquake hit Chino Hills in 2008.

Significant earthquakes were far more common in the Los Angeles Basin the 1980s and the 1990s, in which the 1987 Whittier Narrows earthquake, the 1991 Sierra Madre earthquake and the 1994 Northridge earthquake occurred.

Monday's earthquake was followed up by seven smaller temblors, with two registering as magnitude 2.5 or greater, according to the U.S. Geological Survey.

The seven quakes all occurred about five to six miles northwest of Westwood, with a magnitude 2.5 temblor hitting at 10:07 a.m. Most of the aftershocks were magnitude 1.3 or smaller, according to the USGS.

Monday's quake struck the northern edge of the Santa Monica Mountains, an area that has not seen much recent seismological activity.

“The location is somewhat surprising. It’s within the Santa Monica Mountains. We have not seen seismicity in it in recent times,” Hauksson said. “It has been dormant for quite some time.”

In contrast, there are well-known faults to the south of the Santa Monica Mountains: the Santa Monica and Hollywood faults roughly along Santa Monica and Hollywood boulevards.

The largest and most dangerous earthquake fault closest to Monday’s quake is the Santa Monica fault, which could produce a magnitude 7.0 earthquake underneath Santa Monica Boulevard. The chance of Monday’s quake causing such a massive shaker on the Santa Monica fault, however, is a small one. There was a 5% chance just after the 6:25 a.m. earthquake, but that risk will fall to 1% by Tuesday morning, said U.S. Geological Survey seismologist Lucy Jones.

Also close by is the Hollywood fault, which is near Hollywood Boulevard.

The quake was felt over a large swath of Southern California but especially on the Westside and in the San Fernando Valley.

Aaron Green, 28, a post-doctorate student in chemistry, was asleep at his apartment on Landfair Avenue when he felt a shake: boom-boom, boom-boom.

"I just figured the neighbors upstairs we're gettin' to it," he said. "But it was a little more vigorous than normal. Pretty surprising, and a little scary too."

Cristina Toth, 26 and Andresa Maia, 25, were among the few that were not shaken awake by the earthquake at UCLA. The two master's students were making a model for their architecture final so they were up all night.

Still, Toth said the shaking "kind of freaked us out." UCLA's architecture building is old, the students said, a fact they realized after they had fled the scene. "We looked at each other," Maia said, "and we just sort of ran outside."

Quake another win for early-warning system (8:54 a.m.)

The earthquake demonstrated the success of an early earthquake warning system being tested by scientists at the U.S. Geological Survey. The center’s offices in Pasadena received some seconds of early warning. The farther an earthquake epicenter is away, the more seconds of warning the system can provide.

“It certainly worked in terms of notifying ahead of time, before the shaking arrived,” Graves said.

According to the USGS, the epicenter was six miles from Beverly Hills, seven miles from Universal City and seven miles from Santa Monica.

In the last 10 days, there have been no earthquakes of magnitude 3.0 or greater centered nearby.

This information comes from the USGS Earthquake Notification Service.

Quake can be teachable moment (8:19 a.m.)

Nancy King, geophysicist with the U.S. Geological Survey, said: "We live in earthquake country and we can expect earthquakes frequently and the big one, one day. We don’t know when that one’s coming.”

King said she hopes Monday’s earthquake can be used as a teachable event for residents to be better prepared for earthquakes.

“We need to get ready and I think the good news about earthquakes is you can get ready,” she said, adding that residents can do things such as bolting down heavy furniture and securing bookcases that could help dramatically during a strong event.

Garcetti wants earthquake review (8:02 a.m.)

L.A. Mayor Eric Garcetti confirmed the city has no reports of damage.

"Today's earthquake is a reminder that every L.A. family must be prepared with food, water and other essentials, as well as a plan," the mayor said in a statement. "While it appears the greatest impact of this temblor was a rude awakening, we are executing our post-earthquake protocols to survey our neighborhoods and critical infrastructure. I have been briefed by my science advisor for seismic safety, Dr. Lucy Jones, and will continue to monitor the situation."

Largest quake in L.A. area since 2008 (7:52 a.m.)

Robert Graves, a seismologist with the U.S. Geological Survey, told reporters that Monday’s earthquake was the most significant shake in this Southern California area since the magnitude 5.5 earthquake in Chino Hills in 2008.

Graves said there have been a couple of aftershocks already since the magnitude 4.4 earthquake struck six miles from Westwood at 6:25 a.m. Monday. Graves said there is always the small possibility that the 4.4 earthquake was only a prelude to an equal or stronger shake.

“Always the possibility that it’s a foreshock,” Graves said, adding that about 5% of earthquakes are followed by an equal or larger shake and that if it does happen, it would occur within the next several hours.

2.7 quake reported (7:34 a.m.)

A 2.7 quake, likely an aftershock, was recorded at 7:23 a.m. in the same area.

 'It was a horrible feeling' (7:30 a.m.)

Olga Rosas was sitting up in her bed at her Valley Village home when her boyfriend called her on her cellphone. Then the shaking started.

“It was a horrible feeling,” she said in a telephone interview.

Twitter felt the quake, too (7:16 a.m.)

Here are some reactions from Twitter:

 

News anchors at @KTLA dive beneath their desk as 4.4 quake strikes Los Angeles at 6:25am. Smart move. pic.twitter.com/7zCsVwpp3s

— Michael Linder (@michaellinder) March 17, 2014

A 4.4-magnitude earthquake rattles Los Angeles: http://t.co/2M2AYByaMu pic.twitter.com/2Hubg3ZjHG

— Mashable (@mashable) March 17, 2014

Whoever named it the #ShamrockShake wins Twitter. You may now collect your prize.

— Marc Brown (@ABC7Marc) March 17, 2014

Epicenter near Mulholland Drive and 405 (7:06 a.m.)

The quake was centered not far from the intersection of Mulholland Drive and the 405 Freeway.

'Felt like a sudden shake' (6:58 a.m.)

California Highway Patrol Officer Monica Posada said there were no reports of any immediate problems on the freeways because of the earthquake. The Los Angeles County Sheriff’s Department and the Los Angeles County Fire Department also said there were no reports of immediate damage.

“We did our initial survey and it was felt only. No reports of any damage,” Fire Supervisor Michael Pittman said.

Stacey Dirks, the 25-year-old assistant manager at Noah’s New York Bagels in Westwood, was at work at the time and said “it just felt like a sudden shake, it was just like rapid and quick.”

No bagels fell off the shelves and “everything stayed in place,” Dirks said.

Joe Ramallo of the Los Angeles Department of Water and Power said that as of 6:45 a.m. there were no reports of water main breaks or power outages immediately following the earthquake. But he said crews are conducting routine safety checks after the quake to ensure their durability.

Quake strongest on Westside, Valley  (6:46 a.m.)

The quake was felt most strongly in the Valley and Westside. According to the USGS "Did You Feel It" service, people reported feeling shaking as far east as Perris and as far south as San Clemente.

The LAFD said it is in "earthquake emergency mode as crews survey our city by ground and air; there are NO reports yet of any quake related injuries or damage."

Downgraded to 4.4 (6:41 a.m.)

The USGS downgraded the quake to a 4.4 magnitude from 4.7. A spokesman for the Los Angeles Fire Department said there were no immediate reports of any damage or injuries. A spokeswoman from the Los Angeles Police Department also had no reports of damage.

Quake felt over large area (6:38 a.m.)

The quake was felt over a large area of Southern California. Metro said there might be some delays due to the temblor.

Read more about Southern California earthquakes.

The original post about this earthquake was created by information from the USGS Earthquake Notification Service and an algorithm written by Times digital editor Ken Schwencke.

[For the Record, 6:48 p.m. PDY, March 17: An earlier version of this post misspelled the first name of student Cristina Toth as Christina.] 

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ari.bloomekatz@latimes.com

ron.lin@latimes.com

matt.stevens@latimes.com

Copyright © 2014, The Baltimore Sun
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