Wired: HOW YOU COULD GET AN EARLY WARNING FOR THE NEXT BIG EARTHQUAKE

“Using a free app called QuakeAlert, two beta-testers who work at the University of California Berkeley received notifications—though only two and five seconds before feeling the quake. Two others, up near Sacramento but close enough to register intensities over 2.0, received push alerts a full 27 seconds before any noticeable tremors.”

Source: https://www.wired.com/story/how-you-could-get-an-early-warning-for-the-next-big-quake/