abstract

A systematic study has been made of the ratios of (displacementperiod) of PcP, PcS, ScS, and ScP to that of the corresponding incident wave {e.g.,(displacementperiod)PcP/(displacementperiod)P}, using intermediate and deep-focus earthquake seismograms. The results indicate that the observed ratios of the horizontal components of the waves that are reflected as P waves (i.e., PcP/P and ScP/S) and that of the vertical component of the waves that are reflected as S waves (i.e., ScS/S and PcS/P) at the mantle-core boundary are considerably larger than the theoretical ones, whereas the observed ratios of the vertical component of the first group and that of the horizontal component of the second group are in fairly good agreement with the theoretical values. Theoretical computations were based on the assumption that in the case of a longitudinal wave the vibration is in the direction of propagation and in the case of a transverse wave the vibration is perpendicular to the direction of propagation. It is further found that the behavior of the direct P and S waves is in accord with the theory, but the vibration of the ground is not in the direction of propagation for PcP and ScP and is not perpendicular to the direction of propagation for PcS and ScS.

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