A NEW SEISMIC DAMAGE PREDICTION METHODOLOGY OF WATER SUPPLY PIPELINES FOR WIDE REGIONS; APPLICATION TO THE 2004 NIIGATA-KEN CHUETSU EARTHQUAKE, JAPAN

Abstract

  Conventional damage predictions methodologies of lifeline structures are mainly based on peak ground motion measures. However a line structure such as a lifeline suffers damage mainly induced by the strain of the ground, and therefore is likely to be vulnerable to sharp spatial changes in ground motion. In this study we propose a measure of water supply pipeline (WSP) damage based on the spatial gradient of peak ground velocity (PGV), as an attempt to quantify the effect of geospatial variability of ground motion into lifeline damage. We investigated the spatial distribution of damage to WSP during the 2004/10/23, M6.8 Niigata-ken Chuetsu earthquake, and compared the surveyed damage with the PGV distribution as well as with the gradients of PGV calculated around the source area. In order to allow a comparison between ground motions and the very dense observed damage to WSP, we calculated the PGV distribution for a region around the source area at a grid cell every 250 m. We estimated ground motions by applying a broadband frequency strong ground motion simulation methodology based on a multi-asperity source model of the Chuetsu earthquake. Then we calculated the gradients of PGV along the geographical coordinates, and define the PGV gradient vector amplitudes as a damage estimator.   Our results show that the distribution of damage to WSP has a very good correlation with the gradients of PGV, in contrast with a poor correlation with PGV. We show that the predicted PGV values and the gradient of PGV are useful indexes for a first screening evaluation of hazard maps of roads and underground facilities like WSP.