In the geodynamic context of the slow convergence between the African and Eurasian plates, the Central Mediterranean region has been involved in a complex subduction process that over the last 30 Myr was characterized by the rapid retreat of the Ionian trench, the opening of back-arc extensional basins (i.e., Liguro-Provençal, Algerian, and Tyrrhenian basins) and episodes of slab lateral tearing, segmentation,

The Central-Western Mediterranean (CWM) is one of the most complex tectonic setting on Earth. Episodes of slab rollback, break-off and tearing, the opening of back-arc extensional basins (i.e., Liguro-Provencal, Alborean, Algerian and Tyrrhenian basins), the presence of large mountain ranges, active volcanoes and violent earthquakes have made the Mediterranean an ideal environment to study a wide range of geodynamic processes and an important target for seismological studies (e.g, seismic tomography). Here we build a geodynamic model which, although it does not reproduce its exact tectonic structure (e.g., due to the limits of the numerical method, approximations in the initial setup, etc), presents multiple and geometrically complex subduction systems analogous to those found in the CWM. The tectonic evolution of this model is estimated with petrological-thermo-mechanical 3D simulations, then, we dynamically compute the upper mantle fabrics and seismic anisotropy as a function of the strain history and local P-T conditions. After comparing the model with SKS splitting observations in order to quantify the discrepancies with the true Central-Western Mediterranean, we use the elastic tensors predicted for the modeled configuration to perform 3D P-wave anisotropic tomography by inverting synthetic P-wave delay times. Using the geodynamic model as reference, we evaluate the capabilities of a recently developed seismic tomography technique to recover the isotropic anomalies and anisotropy patterns related to a complex subduction environment in different conditions, such as poor data coverage and bad data quality. We observe that, although P-wave tomography still remains a powerful tool to investigate the upper mantle, the reliability of the retrieved structures strongly depends on data quality and data density. Furthermore, the recovered anisotropic patterns are consistent with those of the target model, but in general an underestimation of the anisotropy magnitude in the upper mantle is observed. In the light of future developments, our study suggests that by combining micro- and macro-scale geodynamic simulations and seismological modeling of seismic anisotropy it will be possible to reproduce, at least to a first order, the tectonic evolution of real study regions (e.g., the Mediterranean) thus providing fundamental constraints on the processes that have contributed in shaping their current geological scenario.

<p><span class="Apple-converted-space"> </span>Characterized by persistent eruptive activity associated with a complex interaction between magma in its plumbing system and an articulated tectonic and geodynamic context, Mt. Etna (Sicily, Italy) is one of the most hazardous and monitored volcanoes in the world. Since the late 1990s, several seismic and tomographic experiments have been performed to obtain accurate images of the shallow-intermediate P-wave velocity structures of the volcano. Unfortunately, seismic tomography models, in particular those derived from body waves, typically relies on the approximation of seismic isotropy. This is a poor assumption considering that P-waves exhibit strong sensitivity to anisotropic fabrics and neglecting anisotropic heterogeneity can introduce significant velocity artefacts that may be misinterpreted as compositional and thermal heterogeneities (VanderBeek & Faccenda,2021; Lo Bue et al, 2022). Here, we discard the isotropic approximation and invert for P-wave isotropic (mean velocity) and anisotropic (magnitude of hexagonal anisotropy, azimuth and dip of the symmetry axis) parameters using the methodology proposed by VanderBeek & Faccenda (2021). We use active and passive seismic data collected by the TOMO-ETNA experiment (Ibanez et al. 2016a, b; Coltelli et al. 2016) between June and November 2014. We present 3D anisotropic P-wave tomography models of Etna volcano and compare them with purely isotropic images. Discriminating the anisotropic structures from the velocity artifacts allows to better recover the isotropic and anisotropic crustal structures and to improve our understanding on the major regional fault systems and on the processes that control magma and fluids ascent beneath the volcanic edifice.</p> <p> </p> <p>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. <em>Annals of Geophysics</em>.</p> <p>Ibáñez, J. M., Prudencio, J., Díaz-Moreno, A., Patanè, D., Puglisi, G., Lühr, 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. <em>Annals of Geophysics</em>, <em>59</em>(4), S0426-S0426.</p> <p>Ibáñez, J. M., Díaz-Moreno, A., Prudencio, J., Patené, D., Zuccarello, L., Cocina, O., ... & Abramenkov, S. (2016b). TOMO-ETNA experiment at Etna volcano: activities on land. <em>Annals of Geophysics</em>, <em>59</em>(4).</p> <p>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. <em>Frontiers in Earth Science</em>, <em>10</em>, 884100.</p> <p>VanderBeek, B. P., & Faccenda, M. (2021). Imaging upper mantle anisotropy with teleseismic P-wave delays: insights from tomographic reconstructions of subduction simulations. <em>Geophysical Journal International</em>, <em>225</em>(3), 2097-2119.</p> <p> </p>

<p>Despite the well known anisotropic structure of Earth’s upper mantle, the effect of seismic anisotropy on the construction of body wave shear velocity models remains largely ignored. Ignoring anisotropic heterogeneity can introduce significant model artefacts that may be misinterpreted as compositional and thermal heterogeneities. While effective anisotropic imaging strategies that improve model reconstruction have been developed for P-wave delay times, no such general framework exists for S-waves partly because, unlike P-waves, there is not a simple ray-based methodology for predicting S-wave travel-times through anisotropic media. Here, we apply a new methodology for the inversion of relative shear wave delay times and splitting intensity measurements for arbitrarily oriented hexagonally anisotropic model parameters using data collected across the western United States and Cascadia subduction system. We detail the data analysis procedure required for making measurements of shear wave observables suitable for anisotropic inversions (e.g. determination of incoming polarisation directions). We then present a preliminary anisotropic shear wave velocity model for Cascadia and compare the results to purely isotropic images. The imaged anisotropic heterogeneity is compared to the well-established patterns in shear wave splitting parameters observed in the study area.</p>

Each year, hundreds of deliveries all over Europe occur precipitously outside of the hospital setting. We report our experience concerning two labors and deliveries resulted in good outcomes in an helicopter. Between February and November 2020, two infants were born during helicopters flights with the assistance of physician and nurse.