LOS ANGELES — The 5.2-magnitude earthquake in SoCal on April 14 saw millions receiving ShakeAlert early earthquake warning messages on their smartphones, including users of the MyShake app and those receiving notifications through wireless emergency alerts as well as Google alerts.

The ShakeAlert Earthquake Early Warning System is managed by the U.S. Geological Survey and detects earthquakes quickly enough for alerts to be delivered potentially seconds before the shaking starts. 

ShakeAlert is the only public EEW system in the U.S., serving more than 50 million residents and visitors in California, Oregon and Washington.