Deployment of dense nodal network during unrest: investigation of the Vulcano-Lipari System (Italy) with Local Earthquake Tomography

The Vulcano-Lipari System is a volcanic complex located in the central sector of the Aeolian Archipelago in southern Italy. The edifice is affected by complex tectonics and develops upon the trans-extension of the Aeolian-Tindari-Letojanni Fault System. This fault is proposed to control magmatism and acts as a preferential pathway for upwelling of magmatic and supercritical fluids. Over the last three decades, Vulcano Island underwent several volcanic crises and since September 2021 it has been showing signs of increasing activity and volcanic unrest. Temperature, degassing, seismic activity, and deformation rapidly increased causing temporal evacuation of the inhabitants of the most affected regions. During the unrest in October 2021, we deployed 196 3C geophones all around Vulcano and south of Lipari to record the seismic signals for a full month, as part of the VulcaNODES project. The resulting seismic catalog confidently contains more than 7000 volcano-seismic and volcano-tectonic events with an average local magnitude of -0.32. This catalog is used to produce an unprecedented travel-time time-lapse tomography of the unrest. Seismic tomography is a powerful tool for observing structures at depth beneath volcanic systems, using seismic waves generated by earthquakes. Such a dense network combined with the exceptional seismic signal recorded will provide tomographic time series of the plumbing system every 1-3 days for a month. The still ongoing VulcaNODES project aims at observing fluids evolution along the volcano’s tectonic structures on a daily basis, providing new insights on processes usually difficult to record on short timeframes, and shedding light on the plumbing system on a high resolution.