The free app, MyShake, "uses smartphone sensors to detect movement caused by an earthquake," then reporters write. "Users who download the app will be sending data to scientists when an earthquake as small as a magnitude 5 hits. By harvesting information from hundreds of phones closest to the earthquake, scientists will be able to test a computer system that could, in the future, dispatch early warnings that shaking is seconds or minutes away to people farther away from the earthquake’s origin."
Richard Allen, director of Berkeley's seismological lab, said if "at least 300 phones [are] sending warnings in the same 60-mile-by-60-mile zone, simulation tests show that’s good enough to tell the system that the shaking was an earthquake," reports the Times. "The warnings will eventually give trains time to slow down, decreasing a risk of derailment before shaking arrives, sound an alert in hospitals to warn surgeons to halt surgery, and have elevators open their doors at the nearest floor, preventing people from becoming trapped."
Allen told the Times, “This is an app that provides information, education, motivation—to the people who’ve downloaded it—to get ready for earthquakes. Those same people are contributing to our further understanding of earthquakes, because they’re collecting data that will help us better understand the earthquake process.”