A 10,000-kilometre-long fibre-optic cable owned by Google that is at the bottom of the Pacific OceanĀ can be used to detect deep-sea seismic activity and ocean waves.
Zhongwen Zhan at the California Institute of Technology in Pasadena, California, and his colleagues, including researchers at Google, used traffic data from one of the tech giantās optical fibres to measure changes in pressure and strain in the cable. Using this data, they could detect earthquakes and ocean waves called swells generated by storms.
Over a nine-month period, the team recorded around 30 ocean storm swell events and around 20 earthquakes over magnitude 5 ā strong enough to damage buildings ā including the . The team had wanted to measure a tsunami, but none occurred during the monitoring.
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Deploying and maintaining geophysical instruments on the seafloor is difficult and expensive, so underwater seismic stations are relatively rare. Anthony Sladen at the University CĆ“te dāAzur in France says that the study is āa major step in exploiting the benefits of existing cablesā.
There have been previous efforts to use fibre-optic cables as seismic sensors, but these required specialised laser-detection equipment at both ends of the cable or the use of dedicated fibres within the cables. Such fibres are in short supply on deep-sea cables, so dedicating one to measuring earthquakes would be difficult.
Zhan says his teamās approach of using an existing traffic fibre is more flexible and scalable as it doesnāt need new infrastructure. āThis is exciting as if only a fraction of the million kilometres of submarine fibre-optic networks could be used as sensors, there would be vast improvements in the amount and coverage of seismic data.ā
Science
