Quake is Largest to Hit L.A. Area in 3 Years
ANZA, Calif. — Monday morning’s earthquake was the strongest to hit the Los Angeles region in three years, and has produced more than 100 aftershocks.
The magnitude 4.7 quake struck at 9:56 a.m. and was centered about 12 miles east southeast of Anza in the Riverside County desert.
It caused no major damage, but it knocked items off shelves and was felt over what seismologists said was an unusually large area — including in Hollywood.
That’s because the quake happened in the San Jacinto Mountains, which are composed of hard granite that transmits energy more efficiently.
The quake occurred along the San Jacinto fault zone, which runs through San Bernardino, Riverside, San Diego and Imperial County roughly parallel to the San Andreas fault.
It’s one of three fault zones that absorb friction from the motion of the North American continent and the Pacific plates rubbing against each other.
“It’s capable of generating moderate to large earthquakes,” said USGS seismologist Robert Graves.
“Today’s activity was not out of the ordinary. Actually, it’s pretty typical of the area.”
There is some evidence that the largest quake ever recorded in the fault zone, of magnitude 7, occurred sometime in the early 1800s, Graves said.
The fault zone has generated eight earthquakes of magnitude 6 or larger in the last century, Graves said.
About five earthquakes of similar size have occurred within 20 kilometers of the area within the last 20 years, he said.
The most recent large earthquake in the fault zone was the magnitude 6.5 Borrego Mountain earthquake in 1968.
It severed power lines in San Diego County, cracked plaster in Los Angeles and rocked boats in Long Beach for five minutes, according to Caltech’s website.
That quake struck just a few miles to the south of Monday’s earthquake.
-KTLA/Los Angeles Times