振源近傍における粘弾性多層構造地盤の振動特性について

Abstract

The characteristics of vibrations of layered viscoelastic ground are investigated theoretically inthe case of the harmonic vibration of the surface of that ground. The sources considered are asfollows: (1) a vertical point force, (2) a horizontal point force.Integral expressions for the displacement fields are derived by using a technique applied firstby N. A. Haskell to seismological probrems. The integrals are calculated along the real axis.The numerical results are plotted for the frequency characteristics of the amplitudes of dis-placement and for the variations of the amplitudes with the increase of the distance from the source.When the layered medium is composed of alluvial soils, the peak of the second mode in the curvesof the frequency characteristics at the points remote more than one wave length from the sourceare negligiblly lower than that of the fundamental mode. In the latter case, the amplitudes decreasewith the increase of the distance in the similar manner as the surface waves, when the points aremore than one wave length from the source. And the displacement may be expressed in the pro-duct as (34), in that range.