Affiliation: | University of Luxembourg, rue Coudenhove Kalergi, 6, L-1359;Luxembourg, Grand-Duchy of Luxembourg. E-mail: European Center for Geodynamics and Seismology and Natural History Museum of Luxembourg, 19;rue Josy Welter, L-7256 Walferdange, Grand-Duchy of Luxembourg. E-mail: Observatoire Royal de Belgique, avenue Circulaire, 3, B-1180;Bruxelles, Belgium. E-mails:; |