Monitoring seafloor displacement offshore Mount Etna: Evidence for active deformation from acoustic geodesy

Mount Etna, largest and most active volcano in Europe, is located on the east coast of Sicily. Continuous GPS and InSAR monitoring show the highest displacement rates at the coast reaching up to ~3 cm per year. Information on the dynamics and mechanisms of the submerged offshore domain is completely unknown. In 2016, an acoustic geodetic network of five autonomous seafloor transponders was deployed across a dextral fault north of Catania Canyon. This fault is interpreted as the offshore extension of the Tremestieri Fault System and as the offshore southern margin of the sliding sector of the unstable flank. The seafloor geodetic transponders measure acoustic distances across the fault, absolute pressure and tilt for a period of up to 3 years. In July 2017, we downloaded 14 months of data via an acoustic link. The data show clear evidence for sliding of the volcanic flank towards the Ionian Sea and revealed the first observation of active displacement of an underwater landslide by acoustic geodesy