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Spotting quakes before the shakes

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Photo of a seismograph needle recording vibrations

A new AI system uses gravity to spot big earthquakes
Image: ©iStock.com/Furchin

Every second counts when a big earthquake hits. As soon as an earthquake sensor picks up the tremor, warnings can be sent over the internet, much faster than the shake travels through the Earth. And now, scientists have found a way to detect big earthquakes fast, maybe even before the ground starts to shake!

The key to this new technology is realising how Earth-changing a big quake can be. The 2011 Tōhoku-Oki earthquake in Japan moved some sections of seabed by 50 metres. It moved Earth’s axis of rotation and shortened the length of a day by 1.8 microseconds.

Such a huge event should also affect Earth’s gravity, just a tiny bit. And gravity moves almost instantaneously, much faster than shakes move through rock. But the signal is extremely faint, even for huge earthquakes.

An international team of researchers decided to create an artificial intelligence (AI) to spot these signals. To do this, they generated 500,000 simulated earthquakes to train it on. But before they used those earthquakes, they added old recordings from times when there were no earthquakes. Earthquake sensors have to contend with all kinds of vibration ‘noise’, including trucks, animals, wind and ocean waves, so it was important to include some.

After all the training came the real test. Scientists took recordings from the Tōhoku-Oki earthquake, before and during the shaking. The AI detected the earthquake about as fast as other methods, but it was much better at measuring the magnitude, something that regular earthquake systems have difficulty with during really big quakes.

It’s this magnitude measuring that really has scientists excited. During the Tōhoku-Oki earthquake, early measurements estimated the magnitude at only 8.1, rather than 9.0. This difference might sound small, but a 9.0 earthquake is more than 20 times more powerful and destructive than one at 8.1. And knowing the difference earlier can save lives.

Earthquakes are uniquely powerful and destructive, and the largest ones literally reshape our planet. But this new technique could give us a bit more warning when the next big one hits.

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