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."
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