Abstract
The relation between displacements and periods when the periodic source is considered has been quantitatively investigated for LOVE waves in stratified two layers, however that, for RAYLEIGH waves in those layers, has been obtained only qualitatively in a theoretical expression by TAZIHE (1957, 1965).
In the present paper, the horizontal and vertical surface displacement as a function of period was calculated for the first six modes of dispersive RAYLEIGH waves for various values of POISSON'S ratio in the superficial layer, the values of other elastic constants being unchanged as follows: μ2/μ1=4, υp1/υp2=0.625, σ2=0.25.
According to a theoretical expression of displacements by TAZIME (1965), the predominance of displacements would be expected at the period of a minimum value of the group-velocity, since the displacements are such expressed as they are proportional to the term (c/U-1), where c and U denote the phase- and group-velocity respectively. However, in the present calculation, a maximum value of the displacement is obtained not always at the period of a minimum value of the group-velocity, but at the period between the minimum and maximum group-velocity in a certain case.
The higher modes of LOVE waves are, in general, inferior in the displacement, regard-less of the values of elastic constants. However, the displacements for dispersive RAYLEIGH waves are predominant not always in the lower mode, but in the higher mode when the value of POISSON'S ratio in the superficial layer is larger than 0.35.
As a result, it was found that the quarter wave-length law always holds in the horizontal and vertical displacement for these predominant periods.
