Anthony Sladen, Diane Rivet, Jean Paul Ampuero , Louis De Barros, Yann Hello, Gaëtan Calbris, Patrick Lamare

Two thirds of the surface of our planet are covered by water and are still poorly instrumented,
which has prevented the earth science community from addressing numerous key scientific
questions. The potential to leverage the existing fiber optic seafloor telecom cables that
criss-cross the oceans, by turning them into dense arrays of seismo-acoustic sensors, remains
to be evaluated. Here, we report Distributed Acoustic Sensing measurements on a 41.5
km-long telecom cable that is deployed offshore Toulon, France. Our observations
demonstrate the capability to monitor with unprecedented details the ocean-solid earth
interactions from the coast to the abyssal plain, in addition to regional seismicity (e.g., a
magnitude 1.9 micro-earthquake located 100 km away) with signal characteristics
comparable to those of a coastal seismic station.