But the sensors are surprisingly sensitive, and can also act like a mini seismometer.
Google has introduced a function that allows users to allow their phone to automatically send data to the Android Earthquake Alerts System, if their device picks up vibrations that are characteristic of the Primary (P) waves of an earthquake. By combining data from thousands or even millions of other phones, the system can work out whether an earthquake is happening and where. It can then send out alerts to phones in the area where the seismic waves are likely to hit, giving an early warning.
And because radio signals travel faster than seismic waves, the alerts can arrive before the shaking starts in areas away from the epicentre.
Marc Stogaitis, a software engineer at Android, put it like this: “We’re essentially racing the speed of light (which is roughly the speed at which signals from a phone travel) against the speed of an earthquake. And lucky for us, the speed of light is much faster!”
As most of the data is crowdsourced, the technology opens up the possibility of monitoring for earthquakes in areas where there aren’t extensive networks of expensive seismometers. It means raises the possibility of providing earthquake alerts in even remote and poorer regions of the world.
In October 2022, engineers at Google saw phones across the San Francisco Bay Area light up with earthquake detection data as the seismic waves travelled outwards from the epicentre.
The now system regularly picks up these shakes. Most recently, on the afternoon of 4 April 2023, a magnitude 4.5 earthquake that occurred near Tres Pinos, California was picked up by the ShakeAlert system, triggering messages on the mobile phones of uses in the area. Earthquakes are a common occurrence in California, which experiences up to 100 small quakes a day. Most of these are too small to feel. However, there are typically several larger earthquakes in California per year, with around 15-20 above magnitude 4.0.
More widely, of the estimated 16 billion mobile phones in use around the world, more than three billion run Android on them and the Earthquake Alerts System is now available in more than 90 countries that are particularly prone to earthquakes.
But the system has its limitations, particularly in remote areas where there are few phone users and in quakes that happen offshore, where they can trigger tsunamis. And while it can help issue alerts a few seconds in advance, the science of predicting earthquakes before they happen remains as elusive as ever. (Read more about how scientists are trying to spot the early signs of these natural disasters.)
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