Optical fibers can do more than transmit data—they can actually sense what’s going on around them, including the earliest rumbles of an earthquake.
For the past year, Biondo Biondi, a professor of geophysics at Stanford University, has used a 4.8-kilometer (or 3-mile) test loop of optical fibers installed on the Stanford campus to record vibrations caused by earthquakes, and distinguish those from vibrations caused by other sources, such as passing cars.
His team has recorded 800 seismic events using this fiber optic seismic observatory since September 2016, including signals from the recent Mexico earthquake and vibrations from blasting at quarries in the area. The fibers can distinguish between two types of earthquake waves, the P wave and the S wave. That’s important for earthquake warning systems, because P waves travel faster but S waves cause more damage.
Using optical fibers to monitor seismic events is not a new technology—it’s standard operating procedure for oil and gas companies. However, this involves first stabilizing the fibers by attaching them to a surface, like a pipeline, or encasing them in cement. Biondi’s project used loose fiber optic cables laying inside plastic pipes, mimicking a standard optical communications installation.