The cables we all rely on for high-speed Internet access can also form part of an early-warning system for earthquakes.
The earlier an earthquake can be predicted, the more chance there is of people getting to safety and avoiding serious injury or death. But implementing an early warning system on a scale big enough to protect whole cities is extremely expensive. However, researchers at Stanford University believe they have a cheap solution. It’s cheap because we already installed it!
Stanford geophysics professor Biondo Biondi is leading a research team developing a continuous earthquake monitoring system using optical fibers. Those are the same fibers already present throughout every major city allowing us all to enjoy high-speed Internet access.
Biondi’s group have been experimenting with a three-mile loop of optical fiber installed at the Stanford University campus. Importantly, there is nothing novel about this loop. It’s optical fiber sitting inside a plastic cable under the ground, just like commercial cabling.
The earthquake detection works thanks to acoustic sensing. Light travelling along an optical fiber always encounters impurities and some of the light bounces back. This is known as a “backscatter signal.” What Biondi’s team realized is that “vibration or strain” on the fiber changes the backscatter signal and this can be monitored.