This paper analyzes water pipeline damage during the Niigata Chuetsu earthquake considering seismic intensity and geomorphology. In the analysis, GIS tools, estimation method of ground motion by interpolation, and questionnaire survey for ground motion were used. Pipe failures were mostly caused by ground deformation on the slope triggered by high seismic intensity. We analyzed the effects of slope quantitatively using the estimation formula of pipeline damage and introduced new coefficient of slope applicable to that formula.

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This study deals with the identification of propagating direction of Rayleigh wave by spectral ratio between horizontal and vertical components of seismic ground motions at a site, which is called as H/V spectral ratio. The H/V spectral ratio of Rayleigh wave is well known to be imaginary, which means a phase difference of 90° between the horizontal and vertical components at the free surface. Using this fact, the index IQ (θ) is defined, which indicates the ratio of imaginary parts in the H/V spectral ratio of seismic ground motions. The propagating direction of Rayleigh wave is then estimated using the IQ (θ), in whose direction the IQ (θ) takes a maximum value. It has been shown from the numerical analysis that phase angles of H/V spectral ratio are concentrated on ±90° in the propagating direction of Rayleigh wave.

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