Seismic tomography of the crust underneath the Etna volcano, Sicily

A new tomographic inversion of the velocity structure and hypocenter parameters has been carried out in the Etna area using a remarkably larger seismic dataset than used in the previous investigations. The obtained Vp and Vp/Vs space distributions allow us to detail the already known structural features and to find new velocity anomalies. A major aseismic high-velocity-body is recognized in the upper 10 km beneath the Central Crater area and the southeastern flank of the volcano, interpreted as high-strength magmatic rocks such as cumulites, dike structures, etc. A high level of seismic activity and low Vp values are found immediately to the west and the east of the high-velocity-body, suggesting the presence of highly-fractured weakness zones which, also taking into account the local distribution of seismogenic stress, can be supposed to include paths for magma rising and stationing. Clear evidence is also found of a shallow aseismic low-velocity-zone beneath the volcano’s southwestern flank, corresponding to the volume where previous investigators hypothesized the presence of a magma chamber on the grounds of geodetic data and seismic b-value mapping.