Fibre optic distributed acoustic sensing of volcanic events

Understanding physical processes prior to and during volcanic eruptions has improved significantly in recent years. However, uncertainties about subsurface structures distorting observed signals and undetected processes within the volcano prevent volcanologists to infer subtle triggering mechanisms of volcanic phenomena. Here, we demonstrate that distributed acoustic sensing (DAS) with optical fibres allows us to identify volcanic events remotely and image hidden near-surface volcanic structural features. We detect and characterize strain signals associated with explosions and locate their origin using a 2D-template matching between picked and theoretical wave arrival times. We find evidence for non-linear grain interactions in a scoria layer of spatially variable thickness. We demonstrate that wavefield separation allows us to incrementally investigate the ground response to various excitation mechanisms. We identify very small volcanic events, which we relate to fluid migration and degassing. Those results provide the basis for improved volcano monitoring and hazard assessment using DAS. Fibre Optic Distributed Acoustic Sensing on Mount Etna provides new opportunities for monitoring volcanic processes and demonstrates nonlinear interaction of infrasound wave with scoria layer, mapping its thickness and illuminating hidden structures.

Automated summary

Understanding physical processes prior to and during volcanic eruptions has improved significantly in recent years, but uncertainties about subsurface structures and undetected processes within the volcano prevent volcanologists from inferring subtle triggering mechanisms of volcanic phenomena. This article demonstrates that distributed acoustic sensing (DAS) with optical fibers allows for remote identification of volcanic events and imaging of hidden near-surface volcanic structural features, providing the basis for improved volcano monitoring and hazard assessment.