SUMMARY We present 2-D attenuation images of the Mt Etna volcanic region on the basis of separation of intrinsic and scattering effects. The analysis presented here exploits a large active seismic database that fully covers the area under study. We observe that scattering effects dominate over intrinsic attenuation, suggesting that the region is very heterogeneous. Comparison with analyses conducted at other volcanoes reveals that the Mt Etna region is characterized by high intrinsic attenuation, resulting from the presence of large volcanoclastic deposits at shallow depth. The 2-D distributions of intrinsic and scattering anomalies show the presence of regions characterized by high and low attenuation effects, corresponding to several tectonic and volcanic features. In particular, we identify a high attenuation region in the SW sector of the Mt Etna volcanic complex, which is correlated with high seismicity rates and volcanism. This work supports the hypothesis of a link between the dynamics of the SW flank and the recharge of the volcano in the last decades, occurring under the summit crater and, secondarily, the upper South rift zone.

Determining the location and size of potential magma reservoirs is crucial to constrain the size of future eruptions or eruptive frequency. Magma accumulation and melt migration have been the focus of extensive research at Mt. Etna volcano. Recent geophysical imaging of Mt. Etna has shown the growing importance of several geological bodies in explaining the migration of eruptive materials inside the volcano. One such body, known as the High Velocity Body (HVB), is a highly consolidated structure located below the central-southern part of the volcano. The HVB has been observed in several tomography studies (Giampiccolo et al., 2020 and references therein) and is interpreted as a massive accumulation of intrusions within the sedimentary basement. In addition, new structural elements have been identified tomographically to the west and southwest of the main volcanic edifice (e.g., Díaz-Moreno et al., 2018 and references therein). Despite not being widely discussed and interpreted in studies based on travel time tomography, these bodies have been well resolved using other techniques. In addition, recent studies (Alparone et al., 2015;Barberi et al., 2016) have found a strong association between deep seismicity beneath Mt. Etna and these geological objects, indicating the need for further study. Apparent contradictions between older and newer tomographic images possibly reflect the increased sensitivity of new tomography techniques to rock heterogeneity

We present the first two-dimensional (2-D) spatial distribution of seismic scattering and intrinsic attenuation beneath the Aeolian Islands arc. The Aeolian Islands archipelago represents one of the best examples of a small dimension volcanic island arc characterised by the alternation of different structural domains. Using the seismic wave diffusion model as the basis for the analysis, and using data from an active seismic experiment (TOMO-ETNA), we analysed more than 76,700 seismic paths marked by epicentre-seismic station pairs. Based on frequencies of 4–24 Hz, we identified high regional attenuation, comparable with other volcanic areas of the world. We used two different seismogram lengths, reflecting two different sampling depths, which allowed us to observe two different attenuative behaviours. As in most volcanic regions, scattering attenuation predominates over intrinsic attenuation, but some characteristics are area-specific. Volcanic structures present the highest contribution to scattering, especially in the low frequency range. This behaviour is interpreted to reflect the small size of the islands and the potentially relatively small size of individual magmatic feeding systems. In addition, strong scattering observed in one zone is associated with the northernmost part of the so-called Aeolian-Tindari-Letojanni fault system. In contrast, away from the volcanic islands, intrinsic attenuation dominates over scattering attenuation. We interpret this shift in attenuative behaviour as reflecting the large volume of sedimentary material deposited on the seabed. Owing to their poorly consolidated nature, sediments facilitate intrinsic attenuation via energy dissipation, but in general present high structural homogeneity that is reflected by low levels of scattering. Our results show that this region is not underlain by a large volcanic structural complex such as that beneath nearby Mt. Etna volcano. Instead, we observe dimensionally smaller and isolated subsurface volcanic structures. The identification of such features facilitates improved geological interpretation; we can now separate consolidated marine structures from independent subsurface volcanic elements. The results of this study provide a model for new research in similar regions around the world.