GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 On constraining 3D mantle fow paterns in subducton, mid-ocean-ridge, and plume environments with teleseismic body wave data M. Faccenda1 , B. P. VanderBeek1 1 Dipartmento di Geoscienze, Università di Padova, Padova, Italy Conventonal seismic tomography studies consider the Earth’s interior as mechanically isotropic, despite seismic anisotropy being widely observed. This current standard approach to seismic imaging is likely to lead to signifcant artefacts in tomographic images with frst-order efects on interpretatons and hinders the quanttatve integraton of seismology with geodynamic fow models. In this contributon we use geodynamic and seismological modeling to predict the elastc propertes and synthetc teleseismic P- and S-wave travel-tme datasets for three diferent tectonic setngs: a plume rising in an intraplate setng, a divergent margin, and a subducton zone (Figs. 1, 2). Subsequently, we perform seismic anisotropy tomography testng a recently developed methodology that allows for the inversion of an arbitrarily oriented weakly anisotropic hexagonally symmetric medium using multple body-wave datasets. The tomography experiments indicate that anisotropic inversions of separate and joint P- and S-wave travel-tmes are capable of recovering the frst order isotropic velocity anomalies and anisotropic paterns. In partcular, joint P- and S- wave anisotropic inversions show that by leveraging both phases it is possible to greatly mitgate issues related to imperfect data coverage common in seismology and reduce parameter trade-ofs. In contrast, by neglectng seismic anisotropy, isotropic tomographic models provide no informaton on the mantle fabrics and in all cases are contaminated by strong velocity artfacts. In the inversions the magnitude of anisotropy (as well as that of seismic anomalies) is always underestmated owing to regularizaton procedures and smearing efects. It follows that the true seismic anisotropy of mantle rocks is likely higher than estmated from anisotropic tomographies, and more consistent with predictons from laboratory and numerical micro-mechanical experiments. Altogether, these results suggest that anisotropic body-wave tomography could provide unprecedented informaton about the Earth’s deep geological structure, and that the later could be beter recovered by complementng teleseismic body-wave travel-tmes with other geophysical datasets (Faccenda and VanderBeek, 2023).