Affiliation: | Institute of Geophysics, Charles University, Ke Karlovu 3, 121 16 Praha 2, Czechoslovakia;Institute of Geology and Geotechnics, Czechoslovak Academy of Sciences, V Holešovičkách 41, 182 09 Praha 8, Czechoslovakia;Geophysical Institute, Czechoslovak Academy of Sciences, BočníII, 141 31 Praha 4, Czechoslovakia |