On the “400-Kilometers” Discontinuity in the Mediterranean Area
It has been shown by Schwab et. al.(1974) and Calcagnile and Panza (1974) that the study of Sa waves propagation is an extremely powerful tool for investigating the properties of the so called 400-km discontinuity. Nolet (1977) by using stacking techniques, has obtained the dispersion relations for the first seven Rayleigh modes in Western Europe in the period range typical for Sa waves. Over tectonically heterogeneous areas, like the European-Mediterranean area (Panza et al. 1980), it may be preferable the use of the standard two-station method (Panza, 1976), which allows the sampling of more limited areas, even if by this procedure the accuracy obtainable in phase velocity determinations is less than the accuracy proper of dispersion relations obtained by stacking.
KeywordsRayleigh Wave Baltic Shield Gravimetric Geoid Mantle Transition Zone Rayleigh Mode
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