A consideration of effect of ground upon propagating behavior of seismic motion in the Port island during the 1995 Hyogoken-nambu earthquake.

Abstract

The attenuation of horizontal component and the amplification of vertical component of the seismic motion had been observed in the vicinity of the ground surface of the Port island during the 1995 Hyogoken-nambu earthquake. This behavior in the Port island is similar to the behavior of seismic motion propagation in buildings with a seismic base isolation system. First the observed seismic records in the buildings have been summarized, and next the seismic response analyses of the ground in the Port Island have been carried out. As a result, it has been presumed that that a thin and very soft clay layer within the ground of the Port island had demonstrated the same effect as a seismic base isolation device in the building during the Hyogoken-nambu earthquake.