HOW ANDROID PHONES BECAME AN EARTHQUAKE WARNING SYSTEM

Summary from the TLDR newsletter

The Android Earthquake Alert system, which is on by default in most Android phones, displays a notification to users when there is an earthquake nearby to warn them to get to a safer location. The system uses accelerometers to detect vibrations - an alert is triggered when there is widespread phone activity that matches the pattern expected for an earthquake. As of the end of March last year, the system has sensed a total of 1,279 events, ranging in magnitude from 1.9 to 7.8, of which only three were false positives.