1. Center for Lithospheric Research; Czech Geological Survey; Klárov 131/3 118 21 Praha 1 Czech Republic
2. Ecole et Observatoire des Sciences de la Terre; Institut de Physique du Globe; CNRS UMR 7516; Université de Strasbourg; Strasbourg Cedex France
3. Institute of Geophysics; Academy of Sciences; Boční II/1401 141 31 Prague 4 Czech Republic