Quantifying apparent anisotropy in a chemically heterogeneous Earth's mantle
Abstract
The interpretation of seismic observations of anisotropy is not straightforward. For example, it is well established that a finely layered, purely isotropic medium is equivalent at large scale to a homogeneous anisotropic medium (Backus, 1962) and there is seismological evidence for fine layered media, such as quasi-laminated structures constrained from high-frequency scattered waves (e.g., Furumura and Kennett, 2005; Kennett and Furumura, 2008). Thus, when imaging fine layering with seismic wave data with wavelength larger than the layer's thickness may result in artificial (also called apparent) anisotropy. Recent studies identified families of stable fine scale models that are equivalent to long-wavelength, vertically transversely isotropic (VTI) models (Fichtner et al., 2013; Wang et al., 2013; Bodin et al., 2015), and efforts to consider more general media are currently under way (e.g., Capdeville et al., 2010a,b). However, it is not clear whether the equivalent fine scale models are compatible with the properties of Earth's mantle materials. In this contribution, we quantify apparent anisotropy arising from fine layering by considering a range of realistic Earth's compositions both at grain and rock scale. We show that significant apparent anisotropy can be formed in ideal conditions only in very narrow regions, while in most of the Earth's mantle apparent anisotropy will hardly be detectable. ReferencesBackus, G.E., 1962. J. Geophys. Res. 67, 4427-4440. Bodin, T., Capdeville, Y., Romanowicz, B. & Montagner, J.-P., 2015. In The Earth's Heterogeneous Mantle, pp. 105-144, eds Khan, A. & Deschamps, F., Springer. Capdeville, Y., Guillot, L., Marigo, J.J., 2010a. Geophys. J. Int. 182, 903-922. Capdeville, Y., Guillot, L., Marigo, J.J., 2010b. Geophys. J. Int. 181, 897-910. Fichtner, A., B. Kennett, and J. Trampert, 2013. Phys. Earth Planet. Inter., 219, 11-20. Furumura, T., Kennett, B.L.N., 2005. J. Geophys. Res. 110, 10.129/2004JB003486. Kennett, B.L.N., Furumura, T., 2008. Geophys. J. Int. 172, 363-382. Wang, N., Montagner J.-P., Fichtner, A., Capdeville, Y., 2013. Geophys. Res. Lett. 40, 4284-4288.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMDI43B0353F
- Keywords:
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- 7208 Mantle;
- SEISMOLOGY;
- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS;
- 8147 Planetary interiors;
- TECTONOPHYSICS;
- 8170 Subduction zone processes;
- TECTONOPHYSICS