1. Department of Geosciences; University of Montana; Missoula MT 59812 USA
2. School of Earth Sciences; University of Melbourne; Vic. 3010 Australia
3. Institute of Geoscience; University of Mainz; D-55099 Mainz Germany
4. Center for Lithospheric Research; Czech Geological Survey; Klárov 3 11821 Praha 1 Czech Republic
5. Ecole et Observatoire des Sciences de la Terre; Institut de Physique du Globe; CNRS UMR7516; Université de Strasbourg; 1 rue Blessig F-67084 Strasbourg Cedex France