Jeroen Tromp, Princeton University, Princeton, NJ, United States, Jeannot Trampert, University Utrecht, Dep. of Earth Sciences, Utrecht, Netherlands, Michel Lacerda Marcondes, Lamont -Doherty Earth Observatory, Palisades, NY, United States and Renata Wentzcovitch, Columbia University in the City of New York, Department of Applied Physics and Applied Mathematics, New York, NY, United States