Fibre Optic Cables as Seismic Network

Placing seismometers under the sea is prohibitively expensive but an international team of scientists led by California Institute of Technology (CALTECH) has used fiber optic communications cables installed at the bottom of the North Sea to create a giant seismic network, tracking both earthquakes and ocean waves. The fact that the fiber network was able to detect and record a magnitude-8.2 earthquake near Fiji in August 2018 proves the ability of the technology to fill in some of the massive blind spots in the global seismic network, says Caltech graduate student Ethan Williams. Williams is the lead author of a study on the project that was published by Nature Communications on Dec. 18. "Fiber optic communications cables are growing more and more common on the sea floor. Rather than place a whole new device, we can tap into some of this fiber and start observing seismicity immediately," Williams says. The project relies on a technology called distributing acoustic sensing, or DAS. DAS was developed for energy exploration but has been repurposed for seismology. DAS sensors shoot a beam of light down a fiber optic cable.