1. Institute of Geophysics and Geoinformatics, TU Bergakademie Freiberg, D-09596 Freiberg, Germany. E-mail: helge.simon@geophysik.tu-freiberg.de
2. Centre for Scientific Drilling, GFZ German Research Centre for Geosciences - Helmholtz Centre Potsdam, D-14473 Potsdam, Germany
3. Department of Earth Sciences, Uppsala University, 751 05 Uppsala, Sweden