La zona di transizione stratificata, fra Mantello e Nucleo terrestri, convoglia cospicui sistemi d'onde, specialmente trasversali, fino alle massime distanze epicentrali

Caloi, Pietro

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 62 (1977) no. 6, pp. 816-824

Résumé

In continuation of author's researches on the layered transition zone between Earth's Mantle and Core, by means of the present work, he arrives to the conclusion that this zone generally becomes vehicle of seismic longitudinal waves ($P_{N}P_{N}P$), transversal waves ($S_{N}S_{N}S$) and mixed waves, that—on the whole—can reach the greatest distances (in that case $P_{N}P_{N}P$ precede $PKP_{1}$, towards which they are however in stage of approaching with the distance). In the part channelled, $_{N}P_{N}$ and $_{N}S_{N}$ have a velocity variable from 12,7 to 9,5 km/sec and from 6,5 to 4,5 km/sec ca. respectively. The lower layers conduct the shorter period waves. At the greatest distances, $S_{N}S_{N}S$ result particularly increased. An indirect evidence of existence of the transition zone and of its stratification is provided by the scattering of the $PKP_{2}$-waves, when they cross it and where them come entrapped, more or less temporarily. Conveyed waves by layered transition zone between Earth's Mantle and Core, constitute a decisive contribution to the correct interpretation of earthquakes; in particular of far-earthquakes, in whose seismograms remained some wide zones of uncertain interpretation, now at last explained.