Estimation of response spectra in the severaly damage area during 1995 Hyogo-Ken Nanbu earthquake

This paper was prepared in response to widespread interest in the 17 January 1995 Hyogo-ken Nanbu earthquake. Although the response spectrum is one of tools to grasp the basic reasons of structural damage we could not calculate it in the severely damaged area by this earthquake because observed records of ground motions were not enough near source region. We therefore calculated theoretical acceleration response spectra at the ground surface in the region near the earthquake source based on the spectral moment method. To estimated earthquake motion on the ground surface the theoretical formula of earthquake motion at base rock level was derived. The amplification effect of the ground was introduced by using the multiple reflection theory. Theoretically estimated response spectrum were modified by the response spectra calculated using observed earthquake motions.(AU)

ILAS : A computer program for analyzing lifeline systems

The computer program ILAS (Integrated Lifeline Analysis System) is being developed for lifeline engineers. The ILAS is basically a program designed for analyzing earthquake risk in lifeline systems, and it includes many of the methods and algorithms for calculations proposed by researches.(AU)

Local site effects on weak and strong ground motions at the Ashigara Valley, Japan

In this paper, two main issues are studied using weak and strong motions observed at a vertical array in the Ashigara Valley, Japan. One is identification of body waves and surface waves. The other is the emergence of nonlinearity of soil. We found that in a short period range in the later phases of observed seismograms, vertically propagating S waves are predominant but surface waves are not. We interpret the phenomena that surface waves in a short period range may disappear due to low Q value in the soft sedimentary deposits. It is also found that the main part of the strong motion, whose maximum acceleration is 200 gal and whose duration is 3 sec, has the potential of making the surface soil nonlinear with the order of ... effective shear strain in the soft surface soil, but that the soil returns to the linear range in the part just after the main part (AU)