1. Institute for Geosciences, Department of Geophysics; Christian-Albrechts-Universität zu Kiel; Kiel Germany
2. Now at Statoil ASA; Stavanger Norway
3. School of Cosmic Physics, Geophysics Section; Dublin Institute for Advanced Studies; Dublin Ireland
4. Faculty of Natural Sciences, Department of Applied and Environmental Geophysics; Comenius University; Bratislava Slovakia
5. Institute of Geophysics; Polish Academy of Sciences; Warsaw Poland