Dynamics of Vulcano Island (Tyrrhenian Sea, Italy) investigated by long-term (40 years) geophysical data

Vulcano Island is a composite volcanic edifice located in the south-central sector of the Aeolian Archipelago (Tyrrhenian Sea, Italy). Historic activity has been characterized by frequent transitions from phreatomagmatic to minor magmatic activity. The last eruption in 1888-90 saw powerful explosive pulses and this eruption defines what we call 'vulcanian' also for other volcanoes. Since then, volcanic activity has been in the form of fumarolic emanations of variable intensity and temperature, mainly concentrated at "La Fossa" crater. We investigated Vulcano dynamics through ca. 40 years of ground deformation and seismicity data collected by the discrete and continuous INGV monitoring networks. We considered levelling, GPS, EDM, seismic and tilt data. EDM and levelling measurements began in the middle of the 1970s; since the late 1990s, the EDM benchmarks have been measured using GPS. We performed a data inversion identifying, for the 1999-2013 period, the action of a deflating magmatic source, located under Vulcanello at 4-5 km a.s.l, just at the top of a wide regional tectonic tabular source. We analyzed data on different time-space scales, distinguishing the dynamics of different sectors of Vulcano (Piano, Vulcanello, La Fossa cone and Caldera) and three periods (1974-1984, 1984-1999, 1999-2013) and the time evolution of the dynamics of the island. We also show how the regional tectonic stress plays an important role in the transition of the volcanic system from a phase of stability to one of unrest, inducing the heating and expansion of shallow hydrothermal fluids.