The earthquake of magnitude 4.4 — centered near Highland Park on Monday — came with an early warning from the California Earthquake Warning System.
It was not immediately clear how many people received the alarm.
But it’s the latest example of how the network is growing. Last week alone, more than 5.4 million people received early warnings that expired earthquake with magnitude 5.2 which hit Kern County about 18 miles southwest of Bakersfield.
Here’s what you need to know about the system:
How does it work?
Shaking from an earthquake travels at the speed of sound through rock – slower than the speed of today’s communication systems. For example, it would take more than a minute for a magnitude 7.8 earthquake starting at the Salton Sea, along the state’s longest fault, the San Andreas, to be felt 150 miles away in Los Angeles.
How do I get it?
While Google’s Android operating system comes with a native app, Apple’s iOS system for iPhones does not.
Those with iPhones can receive early warnings about earthquakes by downloading for free MyShake app, developed by UC Berkeley and provided in partnership with the California Governor’s Office of Emergency Services, which alerts users in California, Oregon and Washington. San Diego County also offers free SD Acute app, which includes the ShakeReadySD earthquake early warning tool.
Android phones and those with the MyShake or ShakeReadySD apps installed have the lowest earthquake early warning threshold: They are set to trigger alerts if a quake is estimated to be magnitude 4.5 or higher and the shaking intensity at the phone’s location is expected to be “weak” — defined as level 3 on the Modified Mercalli Intensity Scale.
Researchers are urging California residents to download early warning apps and say it’s not a bad idea to have more than one way to get alerts on your phone. MyShake available for both Apple’s iOS and Android.
What if I don’t have a smartphone?
People who don’t have smartphones or don’t have early warning apps installed can still get earthquake alerts on their cellphones — but only for those where a higher magnitude or higher level of shaking is projected in their location. These alerts are sent via the wireless emergency alert system, similar to Amber Alerts.