Paula Koelemeijer, University College London, Department of Earth Sciences, London, United Kingdom; Royal Holloway University of London, Earth Sciences, London, United Kingdom, Jeff Winterbourne, Independent researcher, London, United Kingdom, Renaud Toussaint, EOST, CNRS, Strasbourg, France and Christophe Zaroli, Institut de Physique du Globe Strasbourg, Strasbourg Cedex, France