Joint Active and Passive P-wave Tomography reveals Mt. Etna's Seismic Anisotropy

&amp;#160;Characterized by persistent eruptive activity associated with a complex interaction between magma&amp;#160;in its plumbing system and an articulated tectonic and geodynamic context, Mt. Etna (Sicily, Italy)&amp;#160;is one of the most hazardous and monitored volcanoes in the world.&amp;#160;Since the late 1990s, several seismic and tomographic experiments have been performed to&amp;#160;obtain accurate images of the shallow-intermediate P-wave velocity structures of the volcano.&amp;#160;Unfortunately, seismic tomography models, in particular those derived from body waves, typically&amp;#160;relies on the approximation of seismic isotropy. This is a poor assumption considering that&amp;#160;P-waves exhibit strong sensitivity to anisotropic fabrics and neglecting anisotropic heterogeneity&amp;#160;can introduce significant velocity artefacts that may be misinterpreted as compositional and&amp;#160;thermal heterogeneities (VanderBeek &amp; Faccenda,2021; Lo Bue et al, 2022).&amp;#160;Here, we discard the isotropic approximation and invert for P-wave isotropic (mean velocity)&amp;#160;and anisotropic (magnitude of hexagonal anisotropy, azimuth and dip of the symmetry axis) parameters&amp;#160;using the methodology proposed by VanderBeek &amp; Faccenda (2021). We use active and&amp;#160;passive seismic data collected by the TOMO-ETNA experiment (Ibanez et al. 2016a, b; Coltelli et&amp;#160;al. 2016) between June and November 2014.&amp;#160;We present 3D anisotropic P-wave tomography models of Etna volcano and compare them&amp;#160;with purely isotropic images. Discriminating the anisotropic structures from the velocity artifacts&amp;#160;allows to better recover the isotropic and anisotropic crustal structures and to improve our understanding&amp;#160;on the major regional fault systems and on the processes that control magma and fluids&amp;#160;ascent beneath the volcanic edifice.&amp;#160;Coltelli, M., Cavallaro, D., Firetto Carlino, M., Cocchi, L., Muccini, F., D'Aessandro, A., ... &amp; Rapisarda, S. (2016). The marine activities performed within the TOMO-ETNA experiment. Annals of Geophysics.Ib&amp;#225;&amp;#241;ez, J. M., Prudencio, J., D&amp;#237;az-Moreno, A., Patan&amp;#232;, D., Puglisi, G., L&amp;#252;hr, B. G., ... &amp; 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&amp;#225;&amp;#241;ez, J. M., D&amp;#237;az-Moreno, A., Prudencio, J., Paten&amp;#233;, D., Zuccarello, L., Cocina, O., ... &amp; 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., &amp; 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., &amp; 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.&amp;#160;