Finite-frequency sensitivity of SK(K)S phases to lowermost mantle anisotropy: Insights from global wavefield simulations with arbitrary anisotropy using AxiSEM3D
Abstract
We present the results of a new numerical approach to model the effects of arbitrary anisotropy on the propagating seismic wavefield in realistic 3-D Earth models using the spectral element solver AXISEM3D. The three-dimensional anisotropic properties in the computational domain is fully described by a fourth-order elastic tensor with 21 independent coefficients. We provide evidence of the reliability of our results by benchmarking them for upper mantle anisotropy models through a series of SKS - SKKS shear wave splitting analyses performed on synthetic seismograms computed for different anisotropic structures with increasing model complexities. We consider i) the simple case of an S wave propagating in a transversely isotropic medium with a horizontal axis of symmetry, ii) a full global wavefield simulation using the PREM model with horizontal transverse isotropy localized in the upper mantle between 24km and 220km. Finally, iii) we use the code to investigate the finite frequency sensitivity of SK(K)S phases to anisotropy in the lowermost mantle. We tested different mineralogies (Post-perovskite, Bridgemeneite, Ferropericlase), deformation style (CPO and SPO) and crystallographic orientations that are consistent with realistic geodynamical lower mantle flow models and mineral-physics data to model the anisotropic structure of the D" layer. We take advantage of the computational efficiency of the method to compute seismic periods (5 to 8s) rarely resolved for global wavefield simulations in anisotropic medium before. Our results highlight the capability of AXISEM3D to handle high degrees of model complexity and its potential for future studies aimed at unraveling the anisotropic nature of the core-mantle boundary region.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI13B0032L
- Keywords:
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- 3902 Creep and deformation;
- MINERAL PHYSICSDE: 7208 Mantle;
- SEISMOLOGYDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS