3D structure of the Earth’s lower mantle Structure tridimensionnelle du manteau inférieur de la Terre

We present an overview of the present knowledge of the Earth’s lower mantle 3D structure, as currently obtained owing to progress, in the last ten years, in seismic tomography as well as forward modelling of seismic travel times and waveforms. We discuss constraints that seismic modelling brings to the debate concerning major geodynamical questions, in particular the issue of global ‘1 layer’ or ‘2 layer’ circulation, of the missing geochemical reservoir, as well as of the role in global dynamics of the thermochemical boundary layer at the base of the mantle.  2003 Académie des sciences/Éditions scientifiques et médicales Elsevier SAS. All rights reserved.