Joint Active and Passive P-wave Tomography reveals Mt. Etna's Seismic Anisotropy
Authors: Lo Bue Rosalia , Faccenda Manuele , Cocina Ornella , Rappisi Francesco , Vanderbeek Brandon Paul 
Published: February 2023

&#160;Characterized by persistent eruptive activity associated with a complex interaction between magma&#160;in its plumbing system and an articulated tectonic and geodynamic context, Mt. Etna (Sicily, Italy)&#160;is one of the most hazardous and monitored volcanoes in the world.&#160;Since the late 1990s, several seismic and tomographic experiments have been performed to&#160;obtain accurate images of the shallow-intermediate P-wave velocity structures of the volcano.&#160;Unfortunately, seismic tomography models, in particular those derived from body waves, typically&#160;relies on the approximation of seismic isotropy. This is a poor assumption considering that&#160;P-waves exhibit strong sensitivity to anisotropic fabrics and neglecting anisotropic heterogeneity&#160;can introduce significant velocity artefacts that may be misinterpreted as compositional and&#160;thermal heterogeneities (VanderBeek & Faccenda,2021; Lo Bue et al, 2022).&#160;Here, we discard the isotropic approximation and invert for P-wave isotropic (mean velocity)&#160;and anisotropic (magnitude of hexagonal anisotropy, azimuth and dip of the symmetry axis) parameters&#160;using the methodology proposed by VanderBeek & Faccenda (2021). We use active and&#160;passive seismic data collected by the TOMO-ETNA experiment (Ibanez et al. 2016a, b; Coltelli et&#160;al. 2016) between June and November 2014.&#160;We present 3D anisotropic P-wave tomography models of Etna volcano and compare them&#160;with purely isotropic images. Discriminating the anisotropic structures from the velocity artifacts&#160;allows to better recover the isotropic and anisotropic crustal structures and to improve our understanding&#160;on the major regional fault systems and on the processes that control magma and fluids&#160;ascent beneath the volcanic edifice.&#160;Coltelli, M., Cavallaro, D., Firetto Carlino, M., Cocchi, L., Muccini, F., D'Aessandro, A., ... & Rapisarda, S. (2016). The marine activities performed within the TOMO-ETNA experiment. Annals of Geophysics.Ib&#225;&#241;ez, J. M., Prudencio, J., D&#237;az-Moreno, A., Patan&#232;, D., Puglisi, G., L&#252;hr, B. G., ... & Mazauric, V. (2016a). The TOMO-ETNA experiment: an imaging active campaign at Mt. Etna volcano. Context, main objectives, working-plans and involved research projects. Annals of Geophysics, 59(4), S0426-S0426.Ib&#225;&#241;ez, J. M., D&#237;az-Moreno, A., Prudencio, J., Paten&#233;, D., Zuccarello, L., Cocina, O., ... & Abramenkov, S. (2016b). TOMO-ETNA experiment at Etna volcano: activities on land. Annals of Geophysics, 59(4).Lo Bue, R., Rappisi, F., Vanderbeek, B. P., & Faccenda, M. (2022). Tomographic Image Interpretation and Central-Western Mediterranean-Like Upper Mantle Dynamics From Coupled Seismological and Geodynamic Modeling Approach. Frontiers in Earth Science, 10, 884100.VanderBeek, B. P., & Faccenda, M. (2021). Imaging upper mantle anisotropy with teleseismic P-wave delays: insights from tomographic reconstructions of subduction simulations. Geophysical Journal International, 225(3), 2097-2119.&#160;