Abstract
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 attenuationviaenergy 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.
Highlights
Volcanologists seek to understand the nature and structure of the Earth by inferring the physical properties of volcanic structures, determining degrees of homogeneity or heterogeneity, and trying to understand the dynamic nature volcanic eruptions
We have presented the first seismic attenuation maps for the volcanic archipelago of the Aeolian Islands
Its physical behaviour from the point of view of attenuation processes is similar to that of other volcanic regions previously studied. As it has been observed, scattering phenomena are more important than dissipative phenomena when they are attenuating the elastic energy of seismic waves
Summary
Volcanologists seek to understand the nature and structure of the Earth by inferring the physical properties of volcanic structures, determining degrees of homogeneity or heterogeneity, and trying to understand the dynamic nature volcanic eruptions. Imaging volcanic structures remains a challenge for the seismological community, even when similar structures have been identified for multiple volcanoes using different methods (e.g., velocity and attenuation from active and passive seismic sources; Zandomeneghi et al, 2008; Zandomeneghi et al, 2009; Rawlinson et al, 2010; García-Yeguas et al, 2012; GarcíaYeguas et al, 2014; De Siena et al, 2014; Koulakov and Shapiro, 2015; Prudencio et al, 2015a; Prudencio et al, 2015b; De Siena et al, 2017; Prudencio and Manga, 2020; Gabrielli et al, 2020). The Aeolian Islands volcanic arc represents a complex case
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