EU researchers are exploring how undersea communication cables can double-up as environmental and seismic sensors—a potential game-changer for early warning systems.
EU researchers are exploring how undersea communication cables can double-up as environmental and seismic sensors—a potential game-changer for early warning systems.
Beneath the world’s oceans, a silent revolution is underway. More than 1.48 million kilometers of underwater fiber-optic cables carry almost all global internet and telephone traffic. Now researchers are showing that these cables can do more than transmit data: they can listen to the planet.
By capturing tiny changes in how light travels through them, these cables can detect shifts in the movement, vibration and temperature of the seabed and water.
An EU-funded research initiative in the emerging field of fiber-optic seafloor sensing has been working on technology to turn the ocean floor into a vast, real-time observatory. The discoveries made should allow scientists to better monitor climate change, track tectonic activity and improve tsunami and earthquake warnings.
Around 70% of Earth’s surface is covered by water, yet most of it is inaccessible to conventional seismological instruments.
„We have excellent satellite coverage of the sea surface“, said Marc-André Gutscher, marine geoscientist at the Geo-Ocean research center in Brest, France. „But deep beneath, where most earthquakes and tsunamis originate, we have very few direct observations.“
That is beginning to change thanks to research into how undersea cables could be repurposed as a global sensing network.
Two complementary techniques dominate the field: Distributed Acoustic Sensing (DAS) and Brillouin Optical Time Domain Reflectometry (BOTDR).
Gutscher led a seven-year EU-funded research initiative called FOCUS that finished in September 2025.
It explored how these two techniques can detect tiny deformations—just one or two centimeters—along active deep-sea fault lines.
To test the concept, the team installed a 6-kilometer-long prototype cable across the seafloor along the North Alfeo Fault off Catania, Sicily. The area is prone to seismic activity as it lies close to Mount Etna, Europe’s largest and most active volcano.
In 1908, a magnitude 7.1 earthquake struck the Straits of Messina between Sicily and mainland Italy, triggering a devastating tsunami that killed more than 80,000 people in one of Europe’s deadliest natural disasters.
