Gravitational Waves Might Allow Us to Detect Earthquakes at the Speed of Light
Earthquakes are, by their very nature, impossible to predict. The best we can hope for is an early warning system that gives people a chance to take cover, but that chance is usually measured in seconds or minutes. Cosmology research might provide a better way. A team from Côte d’Azur University developed a machine learning algorithm that can detect and interpret gravitational waves produced by seismic events at the speed of light.
Currently, our ability to detect the onset of an earthquake is based on several factors, including the proximity of seismic sensors. There are a lot of gaps in coverage, so it is sometimes impossible to alert everyone in the danger zone. Google has tried to fill in the gaps by leveraging smartphone sensors, but there’s only so much you can do when waiting for the Earth to move under a detector.
A seismic wave moves at about six kilometers per second, and larger quakes can saturate sensors and make it harder to detect early. Gravitational waves, however, propagate at the speed of light. Astronomers first detected this phenomenon in 2016 with the Laser Interferometer Gravitational-Wave Observatory (LIGO), which uses sensitive laser detectors to spot tiny spacetime rumbles. Following that discovery, scientists realized that traditional seismic sensors could detect gravitational waves because these events involve significant displacement of mass inside the planet. By stacking multiple detectors on top of each other, it’s possible to identify patterns in gravitational waves to detect earthquakes very quickly.
The team, led by postdoc researcher Andrea Licciardi, trained an algorithm using data from thousands of simulated earthquakes before unleashing it on data records from the 2011 Tohoku quake off the coast of Japan. This seismic event caused a tsunami, killing about 18,000 and severely damaging the Fukushima Daiichi nuclear power plant (see above). The warning came so late that many in the danger zone never knew the wave was approaching, but the algorithm correctly rated Tohoku at a magnitude 9 after just 50 seconds. That’s faster than even the most state-of-the-art warning systems that rely on seismic waves.
That’s the good news. The bad news is that this method is currently only effective on earthquakes rated at an 8.3 or higher. It is also of little use in areas that are already blanketed in seismometers. It might still be of use in tracking large-scale events, which typically begin deep in faults and might not arrive at the surface for ten or 15 minutes. If it only takes a minute for this system to detect an earthquake via gravitational waves, that gives the populace much more time to get to safety. The next step is to see if the system can detect tremors in real-time, but the future could be coming at us at the speed of light.