DI11C-2608
New constraints on the velocity structure at the base of the mantle from the coupling of normal modes
Monday, 14 December 2015
Poster Hall (Moscone South)
Stephanie Durand, LGLTPE Laboratoire de Géologie de Lyon : Terre, Planètes et Environnement, Villeurbanne Cedex, France, Eric Debayle, CNRS, Paris Cedex 16, France, Yanick R Ricard, LGLTPE Laboratoire de Géologie de Lyon : Terre, Planètes et Environnement, 15 parvis Descartes, Villeurbanne Cedex, France, Sophie Lambotte, Institut de Physique du Globe Strasbourg, CNRS, Strasbourg Cedex, France and Christophe Zaroli, Institut de Physique du Globe Strasbourg, Strasbourg Cedex, France
Abstract:
Most recent tomographic models of Earth's mantle based on the joint inversion of surface waves, body waves and normal modes are biased toward even degrees at the base of the mantle because of the use of normal mode splitting coefficients that are only sensitive to even degrees and because of the uneven body-wave coverage at the base of the mantle. We present SEISGLOB2 our new degree 40 shear velocity tomographic model of Earth's mantle. SEISGLOB2 results from the joint inversion of published normal mode data with our surface wave ( around 22,000,000 Rayleigh wave phase velocities measured by Durand et al. (2015)) and body wave (around 400,000 travel times measured by Zaroli et al. (2010)) datasets. We made a major effort to include cross-coupling structure coefficients which provide new and valuable constraints on odd spherical harmonic degrees in the lowermost mantle. These observations provide new constraints on the large scale structure at the bottom of the mantle, with strong implications for outer core dynamics. We will discuss these new constraints on the lowermost mantle structure.
