SSA: Tomography, what comes next? – “Implementation of Spherical Earth for Box-tomography in Regional Scale”

This is the poster that I presented at the Seismological Society of America meeting, “Tomography: what comes next?” that took place in Toronto, Canada, on October 28-30, 2022.

Abstract

We present the development of a computational framework for the full-waveform inversion of the 3D anisotropic structure of the subduction zone of the Ionian slab at the Tyrrhenian Sea (Italy), to a depth of approximately 500 km. Numerical simulations at the desired resolution in a global setting are computationally extremely costly. Therefore, we jointly use spectral-element SPECFEM3D and AxiSEM software in order to implement the so-called “box tomography” [1]. The global simulation is performed with AxiSEM for a 1-D Earth, whereby the wavefield is constructed at the sides of the “box” (studied region), which covers an area of 11° in latitude and 18° in longitude, where it is propagated in 3D with higher detail using SPECFEM3D-Cartesian. We need to apply an orthographic projection prior to implementing the Earth’s curvature in the computational mesh. We test our framework against data of regional quakes and teleseisms, to validate the “spherical” SPECFEM3D implementation and the hybrid AxiSEM- SPECFEM3D, respectively. We use isotropic and anisotropic regional models [2]. The results of the forward simulation are then used for the inversion.

[1] Masson, Y. and Romanowicz, B., 2017. Box tomography: localized imaging of remote targets buried in an unknown medium, a step forward for understanding key structures in the deep Earth. Geophysical Journal International, 211(1), pp.141-163.

[2] Rappisi, F., VanderBeek, B.P., Faccenda, M., Morelli, A. and Molinari, I., 2022. Slab geometry and upper mantle flow patterns in the Central Mediterranean from 3D anisotropic P-wave tomography. Journal of Geophysical Research: Solid Earth, p.e2021JB023488.

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