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4.7 quake renews worries about destructive Newport-Inglewood fault

May 18, 2009 |  6:58 am

No major damage was reported from the magnitude 4.7 earthquake centered in Lennox, but some windows broke near the epicenter. Seismologists suspect that the magnitude-4.7 earthquake that shook a large stretch of Southern California on Sunday night erupted along the Newport-Inglewood fault, which experts have long feared would produce a devastating temblor.

"The initial focal mechanism is consistent with a slip on the Newport-Inglewood fault, which was the source of the damaging 1933 Long Beach earthquake," the U.S. Geological Survey said in a statement. "Two of the early aftershocks, however, are west of the Newport-Inglewood fault trend. Later aftershocks will help to define the fault plane that ruptured."

USGS officials are not sure whether Sunday's temblor occurred on the Newport-Inglewood but noted that a 1920 quake in the same area erupted on that fault line.

The quake hit at 8:39 p.m. and was centered near Lennox, a community between Inglewood and Hawthorne and east of Los Angeles International Airport. Lasting about 15 seconds, the temblor could be felt as far away as the high desert, Indio, Carpinteria and San Diego County. There were no reports of major damage or injuries.

The earthquake was "a bit deep," originating 8.4 miles below the surface, said U.S. Geological Survey seismologist Susan Hough. "That tends to make it less sharp -- less of a jerky, abrupt motion."

As a result, most of the region felt the quake as a rolling motion, though some closer to the center may have felt a jolt.

The Newport-Inglewood fault, beginning just off the Orange County coast and extending 50 miles northwest through Long Beach, Inglewood and into West Los Angeles, is believed capable of generating a quake in the magnitude-7 range and has been the subject of dire quake scenarios because it runs directly under some of the most densely populated areas of Southern California.

Movement along the southern part of that fault caused the 1933 Long Beach quake, a 6.3 temblor centered off Newport Beach that killed 115 people, mainly in Long Beach and Compton. That was the second-largest number of fatalities in a California temblor in recorded history. Damage to school buildings caused by that quake led to major steps toward earthquake-resistant construction in the state.

A study by the Division of Mines and Geology found that a quake along the Newport-Inglewood fault could cause blockage of the Hollywood Freeway at the over-crossings for Hollywood and Sunset boulevards, reduction of the capacity of Los Angeles International Airport to 30% for two days, the indefinite loss of 34% of all hospital beds in Los Angeles and Orange counties, the shutdown of five power plants for three days and impediments in water supplies.

The USGS said in its statement that the Newport-Inglewood fault "was formerly thought to be capable of very large earthquakes. More recent research has shown that, instead, it is of less concern and only capable of up to about [magnitude] 7.4."

Though there was little damage, Sunday's temblor was felt across a wide area.

"It felt like all the windows were about to pop," said Joseph Poindexter, 36, of Los Angeles, who was inside the Hollywood Park Casino. "It sounded like a big sonic boom. Everybody started running or ducking under the tables."

Automatic sensors initially logged a magnitude 5, but as more data came in, seismologists downgraded it to a magnitude 4.7. A brief aftershock, registering 3.1, followed the quake at 8:45 p.m., also centered in the Lennox area.

At the Los Angeles County Sheriff's Department's Lennox station, deputies said the shaking was brief but intense.

"It was pretty strong but over in about 10 seconds," said Lt. Kent Wegener. "There are no [immediate] reports of damage. At this point, we are checking all the critical facilities and getting our ducks in a row."

Los Angeles city and county fire officials also said they had not received significant damage reports in residential or industrial areas, including the coastal refineries.

In Hawthorne, firefighters were called after a lightpole on Chadron Avenue, near Crenshaw Boulevard,  was damaged during the earthquake. One man suffered a heart attack, but it was unclear whether that was connected to the quake.

"Luckily, nothing major so far," said Hawthorne Police Lt. Michael Ishii.

At the South Bay Galleria, south of the epicenter, ceiling tiles fell inside a movie theater. There were no injuries reported, though police were called to the scene to help reunite customers with belongings they'd left inside when rushing for the exits, said Redondo Beach Police Sgt. Scott Weibel.

--Scott Gold, Jean Merl, Jia-Rui Chong, Andrew Blankstein and Rong-Gong Lin II

Caption: No major damage was reported from the magnitude 4.7 earthquake centered in Lennox, but some windows broke near the epicenter.  Credit: Lawrence K. Ho / Los Angeles Times

Times quake map

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USGS summary

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