How Android phones became an earthquake warning system

Summary

If, for some reason, the alert reaches the phone after the seismic waves would have, it simply lets the user know that an earthquake has occurred, and gives them the option of learning more about the event. As of the end of March last year, the system has sent a total of 1,279 events, ranging in magnitude from 1.9 to 7.8, with the largest event occurring in Türkiye. Over that time, software updates have improved the service, with things like the error in magnitude estimates dropping considerably. Some of these things involved improvements in the earthquake modeling based on local conditions in different parts of the world, in terms of both rock structure and building construction. Others were considerably more practical, such as ensuring the alerts didn't include vibrating the phone, which would make them useless for gathering data that would refine location and magnitude estimates. And the system is remarkably fast. A 2023 event that took place 40 kilometers offshore in the Philippines took about 12 seconds before phones on shore started picking up the initial seismic waves. Alerts started going out about six seconds later and gave those who would experience the worst shaking up to 15 seconds of warning. For the larger event in Türkiye, warnings could have been received well over a minute before shaking started. Overall, over a third of the people who could have received alerts say they got one before the shaking started. Roughly a quarter report receiving it during the sharking, and another quarter immediately after the quake became perceptible. Widespread service Of those roughly 1,300 events that triggered alerts, only three were false positives. One of those was triggered by a different system sending an alert that vibrated a lot of phones, something that should be relatively easy to compensate for in software. The other two were both due to thunderstorms, where heavy thunder caused widespread vibrations centered on a specific location. This led the team to bet...