Your Phone Is an Earthquake Sensor

Your phone has a second job. Send this to someone who has no idea. Inside almost every phone there is a small part that senses movement. It is there so the screen knows which way up you are holding it. It turns out that it is also good enough to feel an earthquake.

Imagine thousands of phones on tables and in pockets across one city. One phone shaking means nothing at all. Somebody dropped it. But when a great many phones in the same area shake in the same way at the same moment, that is not clumsiness, that is the ground. The system watches for exactly that pattern, which is why a thunderstorm or a dropped bag does not set it off.

Researchers from Google and the University of California published the results in the journal Science in twenty twenty five. The network now covers ninety eight countries. Warnings arrive somewhere between a few seconds and about a minute ahead of the shaking, which is not much, but it is enough to get away from a window. Be honest about the limits though. In a real survey, only about a third of people got their alert before the shaking started.