Just hours after a moderate earthquake shook most of Southern California, a strong quake struck off the state’s northern coast to become the fourth significant shaker to jolt California this week.
Neither quake Thursday caused serious damage. One person was injured.
A 6.6-magnitude temblor hit about 125 miles off the coast of Eureka around 11:30 p.m. PT, rattling the ocean floor. In the afternoon, a 4.9-magnitude quake struck east of Los Angeles, startling people and knocking items off shelves and desks.
Four significant quakes have hit California this week: A magnitude-5.2 quake shook Riverside County on Sunday, and a magnitude-7.2 quake trembled Tuesday under the ocean 90 miles off Northern California.
Experts not surprised
Stephanie Hanna, a spokeswoman for the U.S. Geological Survey, said Thursday night’s quake was likely an aftershock from Tuesday’s shaker, which prompted a brief tsunami warning for the entire U.S. west coast and part of Canada.
Still, seismologists do not consider it particularly noteworthy that four significant seismic events occurred within a few days in California and off its coast.
“This is an active zone and we can expect moderate to large earthquakes almost at any time in those zones,” said Bruce Presgrave, a geophysicist at the USGS National Earthquake Information Center in Golden, Colo., adding that the events occasionally occur in clusters.
A patchwork of faults crisscrosses California, and the Southern California Earthquake Center recently estimated that a major earthquake beneath Los Angeles could cause up to 18,000 deaths and $250 billion in damage.
Presgrave said it was unlikely the two Thursday quakes were linked to each other.
Lucy Jones, a USGS expert based in Southern California, told NBC News that quakes around 5.0 tend to happen four times a year in California, while those around 7.0 might occur once a year, or once every few years.
As for the possibility of an even bigger quake in the near future, Jones said, "We have a slightly increased chance around the places we've been having them in the last few days and that's part of life here."
'Kind of like thunder'
The afternoon quake was centered near Yucaipa in San Bernardino County, east of Los Angeles, according to the U.S. Geological Survey. About 25 aftershocks followed in a little over an hour, the strongest estimated at magnitude 3.5.
“All of a sudden it just started rocking,” said John Napolitano, a campus police officer at Crafton Hills College in Yucaipa. “I just sat there and rode it out.”
A woman was injured when a light fixture fell on her head in a conference room at Lake Arrowhead Resort, but her injury did not appear to be serious. She was taken to Mountains Community Hospital but did not want her condition made public, a nursing supervisor said Thursday night.
“I heard a loud rumbling sound, kind of like thunder,” said Nick Brandes, manager of a store in Yucaipa. “At the front, all the customers were in a panic. They were all just in a hurry to get out.”
Channon Kelly was eating her lunch in downtown Los Angeles when the quake hit.
“I almost jumped out of my seat,” Kelly said. “I’m starting to get freaked out. We’ve had so many in the last week, the one Sunday and then in Northern California. I could hear the windows rattling and feel it all at the same time.”
None of Southern California Edison’s 4.6 million customers lost power.
