Philippe Jousset (GFZ, Potsdam) "Fibre optic cables, a new tool for seismology and volcanology"

Fibre optic cables are commonly used for data transmission, internet connection, television... In recent years, Earth Sciences benefited from the ability of the fibre glass to be sensitive to quantities such as temperature and strain, using measurements of physical interactions of light sent in fibre glass. After a brief review of optical fibre technologies of interest for Earth Sciences, I will show observations carried out in various geodynamical contexts and geological conditions, such as Iceland, Italy and Germany. Standard telecom fibres deployed for data transmission can be interrogated using Distributed Acoustic Sensing to measure distributed strain with a much higher temporal and spatial sampling than conventional sensors such as seismometers deployed as large-N array. However, the sensing is only sensitive along the fibre. Strain changes associated with earthquakes (attached figure), explosions from volcanoes, or even exploding World War II remaining bombs, can be observed with unprecedented details in space and time. The analysis of the data lead us to discover new seismological and structural features, such as hidden faults and tiny volcanic signals. Optical fibres deployed under the sea can also detect earthquakes, submarine faults, their movements and hydro-oceanic dynamics such as waves. Those examples will illustrate how fibre technologies are revolutionizing our observations and understanding of phenomena in Earth Sciences.