4.8 quake rattles Yuma, followed by aftershocks
Early alert warns wireless device users to take protective action
A swarm of earthquakes jolted Yuma County residents in the early morning hours of Monday, either by the shaking or the emergency alert on their cellphones.
Some residents reported on social media that the shaking woke them, while others reported sleeping through it all.
The earthquakes centered in the area of El Centro and Imperial, California, just west of Yuma.
The swarm kicked off at 1:36 a.m. with a 4.8 magnitude quake with a depth of 11.1 miles and about 2 miles north-northwest of El Centro.
The U.S. Geological Survey recorded another significant earthquake at 1:42 a.m. with a 4.6 magnitude and a depth of 9.8 miles.
After the initial quake, the USGS recorded a series of aftershocks in the next 25 minutes, ranging in magnitude from 2.9 to 4.1, followed by another 14 aftershocks from 2:26 a.m. to 10:36 a.m.
About 2,000 registered users, from Winterhaven to Wellton, reported feeling the earthquake to the USGS. However, the earthquakes did not cause damage or injuries nor did they trigger a tsunami.
What caused the earthquake? “You have two slabs of rock, there’s a lot of stress on those rocks, and occasionally they slip, and when they slip on that fault line that creates the shaking,” said Paul Laustsen of USGS Public Affairs.
“This is the area where the San Andreas Fault starts so it is likely within that fault zone,” he added.
The initial tremor triggered a Shakealert, a relatively new early warning system that warns when an earthquake has been detected and urges individuals to “Drop, Cover, Hold on. Protect Yourself.”
Yuma received the emergency alert on wireless devices about 20 seconds before the shaking rippled across the landscape from El Centro to Yuma.
The goal of Shakealert is
to help people, protect life and property.
“If someone’s doing something, the surgeons at a hospital have scalpels, right? They get a warning, they can put that down. Or we have automated actions, like fire houses that would open up a garage door at a fire department so that their cars can get in and out if the power goes down, and that type of thing,” Laustsen explained.
The Shakealert first debuted in California in 2019. The wireless emergency alerts are sent out through FEMA with the hope that it gives people time to take protective action if they feel shaking.
“You don’t really want to wait till after you find out what’s going on. You just take protective action so that you’re safe, and then assess things once the shaking stops,” Laustsen noted.
Robert degroot, Shakealert operations team lead, was surprised that the alert worked in Arizona.
“Shakealert Earthquake Early Warning System is currently officially operating in California. Oregon and Washington. Not in Arizona,” degroot told the Yuma Sun.
He believes Yuma’s proximity to California is what triggered the alert in this region.
“You’re not far away. That’s fine. I think, irrespective of all this, it’s great. The idea is that people know what to do, of course, if they feel shaking, or if they get an alert to drop, cover and hold on,” he said.
“The idea is about protecting yourself. So earthquakes can potentially cause things to fall off
walls, could cause furniture to fall on people. And so dropping, covering and holding on is what we consider to be the primary way to protect yourself from getting injured. Getting under a table and holding on to that table as it’s potentially moving around the room. And so it’s the whole idea about keeping yourself safe during earthquakes and preventing injury. So drop, cover and hold on,” degroot added.
He explained how the Shakealert works. “We don’t know the earthquake is happening until it reaches the surface of the earth. So we basically detect an earthquake and very quickly process information from that earthquake, and then hand it over to, in this case, FEMA who delivers the alert to your cell phone. This is the Wireless Emergency Alert System, the same system that delivers Amber Alerts. And so the amount of time that you have to take the action depends on how close you are to the epicenter of the earthquake,” degroot said.
He also explained why some people felt the shaking while others did not. “Even though you got an alert, you may not have felt much. There are people probably nearby who did, so we want to keep them safe. Sometimes, you know, if you’re walking or if you’re driving, or if you just happened to be in a certain place, you may not feel it. And that’s just because that’s the way it works. Earthquakes are very complicated beasts. And knowing what they do, what they don’t do, sometimes differs. It depends what floor you’re standing on. Depends on the building you’re on. It depends on whether you’re moving or stationary, lots of things,” degroot said.
“We are prioritizing public safety, keeping people safe … That’s why we have the alerts come to people, to make sure they take that protective action before the worst shaking arrives,” he added.
For more information on earthquakes, go to https:// earthquake.usgs.gov.