Cables as seismic sentinels for submarine earthquakes
S. Himmelstein | March 15, 2021A method to use existing underwater telecommunication cables, which form a network of more than 1 million km of fiber optic cable, to detect earthquakes was demonstrated by an international research team.
Seismic sensing with this submarine infrastructure is effected by analyzing the polarization of laser light traveling through the fibers to detect earthquakes and ocean waves without the need for any additional equipment. Researchers from California Institute of Technology, Google LLC and University of L’Aquila (Italy) applied the technique to the 10,000 km submarine fiber optic Curie Cable connecting Los Angeles and Valparaiso, Chile.
During a nine-month test period, the researchers detected about 20 moderate-to-large earthquakes along The technique was tested on the 10,000 km submarine fiber optic Curie Cable connecting Los Angeles and Valparaiso, Chile. Source: Zhongwen Zhan et al.the cable route, including the magnitude-7.7 earthquake that occurred off Jamaica on January 28, 2020. While no tsunamis were observed, changes in polarization produced by ocean swells that originated in the Southern Ocean were detected and are associated with pressure changes along the seafloor as powerful waves traveled past the cable.
The use of cables as seismic sentinels can provide essential data much faster than current methods, which require minutes for seismic waves to reach land-based seismometers and even longer for tsunami waves to be verified. Polarization can be measured as often as 20 times per second, enabling delivery of a warning to potentially affected areas within seconds.
With the inclusion of machine learning algorithms and automated notification processes, the technique described in Science is expected to improve earthquake and tsunami warning systems worldwide.