GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 1.3 137 MANTLE DYNAMICS AND STRUCTURE FROM COUPLED GEODYNAMIC AND SEISMOLOGICAL MODELLING M. Faccenda Dipartimento di Geoscienze, Università degli Studi di Padova, Padova, Italy The present-daymantle structure is mainly determined bymeans of seismological methods. The interpretation of seismological data (e.g., isotropic and anisotropic velocity anomalies) is however non-unique, as different processes occurring simultaneously can be invoked to explain the observations. A further complication arises when regional tomographic seismic models ignore seismic anisotropy, which generates apparent seismic anomalies due to non- uniform sampling of anisotropic areas. The presence of these apparent anomalies is quite problematic, as they strongly bias our understanding of the Earth’s internal structure. In order to decrease the uncertainties related to the interpretation of seismological observations, geodynamic modelling can be exploited to reproduce the micro and macro scale dynamics and structure of different tectonic settings, yielding a valuable first-order approximation of the rock isotropic and anisotropic elastic properties. The model output can be subsequently tested against observations by performing seismological synthetics (e.g., SKS splitting, travel-time tomography, receiver functions, azimuthal and radial anisotropy). When the misfit between the modelled and measured seismic parameters is low, the geodynamic model likely provides a good approximation of the recent dynamics and present-day structure of the tectonic setting. Such a model can then be used to give a more robust and physically- based interpretation of the observables and/or to further improve seismological models by providing a-priori information for subsequent (adjoint) inversions and/or to test new seismic inversion methods. During the seminar I will show some applications of the methodology and present the new open source software ECOMAN, designed to Explore the COnsequences of Mechanical Anisotropy in the maNtle by means of coupled of geodynamic and seismological simulations. Fig. 1 - Left: geodynamic model of oceanic plate subduction and related seismic properties in spherical coordinates. The model is symmetric with respect to the vertical plane displayed in front. The plate (highlighted by the purple surface indicating +2% isotropic dVp anomaly) rolls back toward the right and finally stagnates into the mantle transition zone. The color scale indicates radial anisotropy, while the white bars at the surface display synthetic SKS splitting data. Right: cover of the ECOMAN software User Manual.