Moderate Earthquake Shakes Southern California
Wednesday, August 8, 2012
A magnitude-4.5 earthquake shook parts of Southern California at approximately 9:30 a.m. on Wednesday morning, according to the U.S. Geological Survey. The quake was centered near Anaheim.
The temblor follows a series of quakes that rattled Southern California this week, including another magnitude-4.5 that struck the same region on Tuesday night.
SDSU Geologist Pat Abbott said the question that remains is whether the quakes are the first in the series.
“Two of them in a row – don’t know if more of them are coming or not," said Abbott. "If these are foreshocks or if they’re two isolated events -- we do not have the ability to recognize a foreshock from a main shock or an aftershock."
The last large quake on the Whittier fault measured magnitude-5.9 and occurred in 1987, toppling houses and parking garages.
San Diego is surrounded by active faults, including the Rose Canyon Fault that runs through the city, said Abbott.
"You could have a 6.4 magnitude just as the northern end of the same fault did in 1933 up in Long Beach. That could any time and it’s right inside the town. That would cause some widespread damage -– Not like Japan, not even as bad as Northridge, but a significant earthquake with significant damage."
Abbott said San Diego's offshore faults are also capable of producing large quakes.
"Everyone of those islands you see out there – Coronado Island, San Clemente Island, Catalina Island – they’re all there because they’ve been lifted up by active faults. And those faults out there could also do things in the 6.5 to 7-point range," he said.
No significant damage or injuries were reported from this week's quakes, but they've kept some residents on edge.
"I was in my dorm at UCSD in La Jolla, felt the one last night and this morning, unsettling! Is this seismic activity more frequent these days or a regular occurrence?" Rene Moraida wrote on the KPBS Facebook page.
"Felt something in City Heights. It was really small," Katherine Ogren wrote.
"I wondered what was happening.. .gave me a visual migraine for real," wrote Mandy Barre.
To view PDF documents, Download Acrobat Reader.