California hasn't stopped shaking after its strongest earthquake in 20 years. The 6.4 magnitude quake that hit the Mojave Desert Thursday morning was followed by at least 159 aftershocks of magnitude 2.5 and higher, including six higher than magnitude 4, says United States Geological Survey seismologist Robert Graves. He says the number is higher than normal, but not unprecedented, CNN reports. California Institute of Technology seismologist Lucy Jones says the quake will probably only have a "minimal" effect on the San Andreas Fault, but the region should still expect more aftershocks and possibly a larger quake, reports the Los Angeles Times. "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," she says.
The quake, which was felt as far away as Las Vegas and Phoenix, hit near the town of Ridgecrest, around 150 miles northeast of Los Angeles. Kern County Fire Chief David Witt says the quake caused multiple injuries and at least two house fires as well as gas leaks and cracked roads in the town of 28,000, the AP reports. Gov. Gavin Newsom has declared a state of emergency for the county. The quake was the strongest in the region since a 7.1 quake on October 16, 1999. Jones says there was an "extremely quiet abnormal time" for 20 years. "The long term average is probably once every five or 10 years somewhere in southern California," she says. KTLA reports that the earthquake did not trigger alerts in Los Angeles because shaking in the area was below magnitude 5. Officials say they plan to lower the early warning threshold for the ShakeAlertLA app. (Read more earthquake stories.)