Analysis Of Earthquake Damage And Restoration Of Water Supply Systems In The2011Off The Pacific Coast Of Tohoku Earthquake

The Great East Japan Earthquake Disaster caused severe damages to water supply systems. Based on the former earthquakes’ experience, many earthquake-resistant measures were taken to improve the water supply reliability, but the countermeasure was not considered sufficient under the large disaster as huge as the Great East Japan Earthquake Disaster. In order to figure out the damages and restoration of water supply system in this event and improve the reliability of water supply in future, this study conducts the analysis below:Firstly, the damage and restoration of water supply systems in the Great East Japan Earthquake Disaster were analyzed. Particularly, in order to understand the damage situation of this event, the damage rate of pipeline was compared with that caused by Hyogoken-Nanbu earthquake.Then among all affected areas in the Great East Japan Earthquake Disaster, Iwaki city and Sennan and Senen area were typical areas suffered from severe damages in water supply. Both water supply system and water supply network in these two areas were selected to conduct more detailed analysis of damage and restoration. In Iwaki water supply system, the damages caused by the main shock were more than that of aftershock. Most damages happened to the VP and DIP, but the damage rate indicated ACP and SP were more vulnerable. The damage rate in aftershock was generally higher than that of main shock. The higher seismic intensity caused lower damage rate in aftershock, but when two shocks combined together, the result indicated the higher seismic intensity led to higher damage rate.95%households were restored after one month, but some areas in Tono, Tabito and Nakoso administrative districts were affected by the aftershock. Although some areas suffered similar number of damages, the restoration days were totally different. Some areas were exposed to the higher seismic intensity, but the restoration days in those areas were less. In Sennan and Senen water supply network,55damages were revealed. The damage to the large diameter of2,400mm was also revealed in this network. All17cities and towns were restored with water supply at Apr.16th.Finally, based on the analysis result of Sennan and Senen water supply network, the reliability of this network was analyzed by Monte Carlo simulation under two scenario earthquakes. The reachability of Nagamachi-Rifu-sen fault earthquake was lower than that of Miyagi-ken Oki earthquake. With the increase of distance of water source to demand nodes, the reachability decreased. Partly looping the network is an effective measure to improve the reliability of water supply, the reachability was increased when6new links added in this network.Based on the analysis in this study of damage and restoration of water supply systems caused by the Great East Japan Earthquake Disaster, the seismic reliability of water supply could be improved in the future.