Non-eruptive unrest and the role of magmatic brines, Vulcano, Italy.

Although not all volcanic unrests lead to eruptions, it is generally accepted that magmatic activity is what causes volcanoes to awake. Alternatively, hydrothermal processes are often invoked to explain inflation and deflation dynamics. Magmatic brines have physical properties in between deep magmas and shallow hydrothermal fluids. Yet, to date we have no physical models accounting for geophysical signals that may be generated by the fluid flow of magmatic brines. Vulcano, the southernmost island of the Aeolian Volcanic Archipelago, Italy, entered into unrest in September 2021. The island experienced intense ground deformation, fumarole temperature and gas emissions increases, and a marked augmentation of seismicity. For the first time since the deployment of broadband stations in 2005, very long period (VLP) seismic events were detected in the seismic records. Certain aspects of the geophysical signals recorded during the unrest are probably not fully compatible with traditional causal models involving fresh magma rising at depth or with a hydrothermal scenario. In this contribution we discuss alternative scenarios and investigate whether fluid flow of magmatic brines may play a key role in understanding volcanicunrests.