Abstract
　The intensity of ground shaking during strong earthquakes is estimated using a response spectrum description of the excitation at the base rock level. Equivalent linearization in corjunction with a step-by-step modal approach is used to compute various statistical measures of the soil response as a function of depth. The characteristic equation for obtaining natural frequencies and mode shapes is obtained using a newly derived solution for the wave transfer function in a multilayered medium with inhomogeneous and nonlinear properties. The solution is also used in conjunction with an existing theory for fatigue failures to investigate the phenomenon of liquefaction in soil layers with arbitrary properties. Incorporation of these results in seismic hazard analysis of lifelines is made possible thmugh the concept of "critica1distance", which is defined as the maximum distance at which an earthquake of given magnitude causes failure. Several example sites with arbitrary geologic profile and soil romperties are investigated and the significance of various factors are determined.

【キーワード】：ライフライン， 破壊ポテンシャル，地盤震動， 液状化

*京都大学防災研究所
Disaster Prevention Research Institute, Kyoto Univ.