The velocity of P-waves below the " 20" discontinuity "

Abstract

Velocity values for P-waves below the " 2 0 ° discontinuit
y " are calculated by applying the Wadati-Masuda method, and by using
separately calculated travel-time curves for the P-waves and the PdPwaves
of each of the five earthquakes examined.
The velocities calculated have a mean value of 10.21 ± 0.24 km/sec,
and are without exception greater than those obtained in a previous piece
of research (9.57 km/sec).
As regards the value of the velocity of the P-waves above the "20°
discontinuity" (8.96 kin/sec), the percentage difference between the velocity
above and the velocity below the "20° discontinuity" is 14%.
Application of the Herglotz-Wiechert procedure in the zone of the
mantle below the "20° discontinuity" does not give significant variations
in the correlation between velocity and depth, in comparison with the results
obtained by other authors.