A day after a 6.4 magnitude quake shook a large swath of Southern California and parts of Nevada, a powerful aftershock measuring 5.4 was reported northeast of Ridgecrest.
The temblor, one of many aftershocks predicted by seismologists, struck the same desert region at 4:07 am (7:07 am ET) on Friday about 11 miles west of Searles Valley, the U.S. Geological Survey said. At least 159 aftershocks of magnitude 2.5 or greater have already been recorded after Thursday's earthquake — the strongest to hit the region in 20 years.
However, there is cause for more concern as experts believe California could be hit by another — and, perhaps, a more powerful — earthquake in the coming days.
US Geological Survey expert Susan Hough told SFGate that for a 6.5 quake you'd expect a lot of aftershocks. "With any earthquake, there is a 5% chance something even bigger will happen within the next three days. If it did, it would be in the same remote area."
Lucy Jones, a seismologist with the California Institute of Technology's seismology lab, said the quake was far enough away from the dangerous San Andreas fault that any impact on the system will be minimal. But bigger quakes are likely, she warned.
“There is about a 1 in 20 chance that this location will be having an even bigger earthquake in the next few days, that we have not yet seen the biggest earthquake of the sequence,” Jones said.
Meanwhile, people in Los Angeles are disappointed that ShakeAlertLA, an earthquake detection app released by the city of Los Angeles earlier this year, failed to alert its users when a 6.4 quake struck near Ridgecrest.
ShakeAlertLA is connected to the US Geological Survey's network of early warning sensors; and it is set to alert cellphone users when the system senses an earthquake of magnitude 5.0 or greater, or with potentially damaging shaking, within Los Angeles County.
But officials say the app did not fail. While Thursday's quake was greater than magnitude 5 in Kern County, in Los Angeles the shaking was below 4.5, the city said.
"The system actually worked as designed," Rob Graves, a seismologist at the US Geologic Survey, told reporters.
The city of Los Angeles said officials will be making adjustments. “We hear you and will lower the alert threshold with @USGS_ShakeAlert,” the city tweeted.
(With AP inputs)