New insights on the active degassing system of the Lipari–Vulcano complex (South Italy) inferred from Local Earthquake Tomography

Abstract

Seismic tomography is a very powerful and effective approach to look at depths beneath volcanic systems thus helping to better understand their behaviour. The P-wave and S-wave velocity ratio, in particular, is a key parameter useful to discriminate the presence of gas, fluids and melts. We computed the first 3-D overall model of Vp, Vs and Vp/Vs for the Lipari–Vulcano complex, central sector of the Aeolian volcanic archipelago (southern Italy). The investigated area has been characterized in recent times by fumaroles, hydrothermal activity and active degassing. In particular, in the Vulcano Island, several episodes of anomalous increases of fumarole temperature and strong degassing have been recorded in the past decades and the last “crisis”, started in September 2021, is still ongoing. For tomographic inversion we collected ~ 4400 crustal earthquakes that occurred in the last thirty years and we used the LOcal TOmography Software LOTOS. The results clearly depicted two low Vp and Vp/Vs anomalies located up to ~ 8 km depths below Vulcano and the western offshore of Lipari, respectively. These anomalies can be associated to the large presence of gas and they furnish a first picture of the gas-filled volumes feeding the main degassing activity of the area.

Imaging volcanoes during unrest: Ambient Noise Tomography of a transient plumbing system, Vulcano, Italy.

“…The outline of the L1 anomaly matches the relatively resistive (2-2.3 Ωm) structure imaged by Di Giuseppe et al 7 and supports the interpretation of an elongated sub-vertical volcanic conduit. Compared to previous local earthquake tomographies 27,60 , we find an opposite situation with the central portion of the cone being affected by low velocities. This may be due to the peculiar conditions under which the current data were acquired.…”