Wouldn't it be great if we could hear about earthquakes in advance? Ideally, we'd get a whole week's warning, but even a single minute could give you time to get to safety, or at the very least to move away from any rickety structures nearby. Yet early earthquake detection systems – based on a delicate system of accelerometers, sensors and computers – are expensive, and are only in widespread use in a couple of places worldwide.
What's been overlooked until now, however, are the one billion tiny earthquake sensors we've all been carrying around in our pockets.
Most modern smartphones contain GPS and satellite navigation sensors – essentially, slightly less sophisticated versions of what are used in earthquake sensing systems anyway. Scientists from US Geological Survey and several US universities drew on this fact to create a concept for a new type of detection system, which would crowdsource information from lots of phones in an area, to watch for oncoming tremors.
Earthquakes take place when the earth, literally, moves; that movement can be picked up by GPS and navigation systems. If a phone and four others nearby detect a displacement of more than 5cm, the researchers' "ShakeAlert" model is "triggered". If the system receives 100 such triggers, an alert is sent out to phones in nearby areas.
This diagram from the researchers shows phones at the earthquake's centre alerting those further away before strong shaking hits their area:
More sophisticated systems can try to predict earthquakes much eartlier through detecting tiny tremors months, or even years, beforehand. But it's always hard to pinpoint exactly when one will happen, and this phone-based model sends out the most urgent message – that the first rumblings of an earthquake have just occured – in an incredibly efficient way.
The researchers are particularly excited that their model could provide warnings in areas that can't afford more sophisticated detection systems. Douglas Given, coordinator of the ShakeAlert system, says:
The US earthquake early warning system is being built on our high-quality scientific earthquake networks, but crowdsourced approaches can augment our system and have real potential to make warnings possible in places that don’t have high-quality networks.
And outside the US, this could be a solution for high-risk earthquake areas, such as Haiti, which may not be able to afford to install large networks of scientific instruments.