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

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