Scientists Turn Undersea Fiber Optic Cables Into Seismographs

Monitoring seismic activity all over the world is an important task, but one that requires equipment to be at the site it's measuring -- difficult in the middle of the ocean. But new research from Berkeley could turn existing undersea fiber optic cables into a network of seismographs, creating an unprecedented global view of the Earth's tectonic movements. Iwastheone shares a report: Seismologists get almost all their data from instruments on land, which means most of our knowledge about seismic activity is limited to a third of the planet's surface. We don't even know where all the faults are since there's been no exhaustive study or long-term monitoring of the ocean floor. "There is a huge need for seafloor seismology," explained lead study author Nathaniel Lindsey in a Berkeley news release. "Any instrumentation you get out into the ocean, even if it is only for the first 50 kilometers from shore, will be very useful." Of course, the reason we haven't done so is because it's very hard to place, maintain, and access the precision instruments required for long-term seismic work underwater. But what if there were instruments already out there just waiting for us to take advantage of them? That's the idea Lindsey and his colleagues are pursuing with regard to undersea fiber optic cables. These cables carry data over long distances, sometimes as part of the internet's backbones, and sometimes as part of private networks. But one thing they all have in common is that they use light to do so -- light that gets scattered and distorted if the cable shifts or changes orientation. By carefully monitoring this "backscatter" phenomenon it can be seen exactly where the cable bends and to what extent -- sometimes to within a few nanometers. That means that researchers can observe a cable to find out the source of seismic activity with an extraordinary level of precision.