Tenth U.S. National Conference on Earthquake Engineering Frontiers of Earthquake Engineering July 21-25, 2014 Anchorage, Alaska

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1 10NCEE Tenth U.S. National Conference on Earthquake Engineering Frontiers of Earthquake Engineering July 21-25, 2014 Anchorage, Alaska COMPARISON OF THE OBSERVED AND ESTIMATED FRAGILITY OF THE WATER DISTRIBUTION SYSTEM OF SENDAI CITY, MIYAGI PREFECTURE DURING THE 2011 TOHOKU EARTHQUAKE Yoshihisa Maruyama 1, Kazue Wakamatsu 2 and Shigeru Nagata 3 ABSTRACT The 2011 off the Pacific coast of Tohoku Earthquake with the moment magnitude of 9.0 caused severe damage to lifeline systems. In Sendai City, Miyagi Prefecture, the suspension of water supply was occurred at approximately 230,000 family units. The interruption of water supply was caused mainly by the earthquake ground motion and the tsunami. This study focuses on the seismically induced damage to water distribution pipeline in Sendai City. The inventory of water distribution pipeline and the locations of pipe breaks compiled by the Sendai City Waterworks Bureau were employed in this study. The total number of pipe breaks was 437 in the dataset. The numbers of damage to vinyl pipes (VP) and ductile cast iron pipes (DIP) were 297 and 117, respectively. No pipe breaks were found at the DIPs with earthquake resistant joints. The seismically induced damage to water distribution pipelines concentrated in the hilly residential areas developed with cutting and leveling the hills and then filling the valleys for the past several ten years. This study investigates the relationship between the damage ratio of water distribution pipeline and ground motion intensity in Sendai City after the 2011 off the Pacific coast of Tohoku Earthquake. The damage ratio is defined as the number of damage incidents per kilometer of water pipe. The correction coefficient for the developed hilly area is proposed to predict the number of pipe breaks of water distribution pipeline. 1 Associate Professor, Dept. of Urban Environment Systems, Chiba University, Japan 2 Professor, Dept. of Civil Engineering, Kanto Gakuin University, Japan 3 Senior Researcher, Technincal Research Institute, Kajima Corporation, Japan Y. Maruyama, K. Wakamatsu and S. Nagata. Comparison of the observed and estimated fragility of the water distribution system of Sendai City, Miyagi Prefecture during the 2011 Tohoku Earthquake. Proceedings of the 10 th National Conference in Earthquake Engineering, Earthquake Engineering Research Institute, Anchorage, AK, 2014.

2 Comparison of the Observed and Estimated Fragility of the Water Distribution System of Sendai City, Miyagi Prefecture during the 2011 Tohoku Earthquake Yoshihisa Maruyama 1, Kazue Wakamatsu 2 and Shigeru Nagata 3 ABSTRACT The 2011 off the Pacific coast of Tohoku Earthquake with the moment magnitude of 9.0 caused severe damage to lifeline systems. This study focuses on the seismically induced damage to water distribution pipeline in Sendai City, Miyagi Prefecture. The inventory of water distribution pipeline and the locations of pipe breaks compiled by the Sendai City Waterworks Bureau were employed in this study. The numbers of damage to vinyl pipes (VP) and ductile cast iron pipes (DIP) were 297 and 117, respectively. The seismically induced damage to water distribution pipelines concentrated in the hilly residential areas developed with cutting and leveling the hills and then filling the valleys for the past several ten years. This study investigates the relationship between the damage ratio of water distribution pipeline and ground motion intensity in Sendai City after the 2011 off the Pacific coast of Tohoku Earthquake. The correction coefficient for the developed hill area is proposed to predict the number of pipe breaks of water distribution pipeline. Introduction The 2011 off the Pacific coast of Tohoku Earthquake occurred on March 11, 2011 with the moment magnitude of 9.0. Lifeline facilities such as electric power supply, water supply, sewage, city gas supply, and telecommunication systems were damaged by ground motion and tsunami. The water supply was disrupted at approximately 2.2 million households [1]. Figure 1 shows the disruption rate of water supply system after the earthquake. The disruption rates more than 75% were observed in the northeastern part of Japan. The water supply system except for the areas affected by tsunami could be restored by the end of September 2011 [1]. Sendai City, Miyagi Prefecture, which is the most populated city in Tohoku District, was affected by both ground motion and tsunami. The number of casualties in Sendai City was approximately 900 (as of February 28, 2013), and most of them were killed by tsunami. The building lots in the hilly areas of the city were affected by ground motion, and 5517 lots were damaged in total [2]. Damage to buried pipelines was also observed in the hilly areas in Sendai City. 1 Associate Professor, Dept. of Urban Environment Systems, Chiba University, Japan 2 Professor, Dept. of Civil Engineering, Kanto Gakuin University, Japan 3 Senior Researcher, Technincal Research Institute, Kajima Corporation, Japan Y. Maruyama, K. Wakamatsu and S. Nagata. Comparison of the observed and estimated fragility of the water distribution system of Sendai City, Miyagi Prefecture during the 2011 Tohoku Earthquake. Proceedings of the 10 th National Conference in Earthquake Engineering, Earthquake Engineering Research Institute, Anchorage, AK, 2014.

3 Disruption rate Unknown 0-25% 25-50% 50-75% % No disruption Fukushima Daiichi Nuclear Power Station Figure 1. Disruption rate of water supply after the 2011 off the Pacific coast of Tohoku Earthquake [1]. The water supply system was interrupted at approximately 230 thousand households in Sendai City. According to the Sendai City Waterworks Bureau, 437 pipe breaks of water distribution pipelines were found because of this earthquake [3]. The vinyl pipes (VP) and ductile cast iron pipes (DIP) without earthquake resistant joints were mainly affected. The seismically induced damage to water distribution pipelines concentrated in the hilly residential areas developed with cutting and leveling the hills and then filling the valleys for the past several ten years. In this study, the relationship between the damage ratio of water distribution pipeline and ground motion intensity in Sendai City after the 2011 off the Pacific coast of Tohoku Earthquake is investigated. The damage ratio is defined as the number of damage incidents per kilometer of water pipe. The damage ratios in the developed hilly areas are compared with those in the other flatlands, which are mainly lowlands and terraces, considering the ground motion intensity. Damage to Water Distribution Pipes in Sendai City, Miyagi Prefecture Table 1 shows the summary of damage incidents to water distribution pipes in Sendai City after the 2011 off the Pacific coast of Tohoku Earthquake. The numbers of damage to VP and DIP were 297 and 117, respectively. No pipe breaks were found at the DIPs with earthquake resistant joints. The overall damage ratio of water distribution pipes, which is defined as the number of damage incidents per kilometer, in Sendai City is apploximately 0.1. The damage incidents due to liquefaction are not reported.

4 Table 1. Summary of damage incidents to water distribution pipes in Sendai City after the 2011 off the Pacific coast of Tohoku Earthquake. Pipe material Damage to pipe body Loose of joint Others Total Length (km) DIP *) VP GP (Galvanized pipe) SP (Steel pipe) Others Total *) No pipe breaks were found at the DIPs with earthquake resistant joints. Figure 2. Locations of damage incidents to water distribution pipes in Sendai City after the 2011 off the Pacific coast of Tohoku Earthquake. Figure 2 shows the locations of damage incidents to water distribution pipes. In the figure, Japan Engineering Geomorphologic Classification Map (JEGM) [4] is also illustrated. The damage to water distribution pipes is observed in lowlands such as alluvial fan, delta and coastal lowlands. In addition to that, it is especially concentrated in the areas where are classified as hill (Fig. 3). The hilly residential areas in Sendai City were affected by the earthquake. Figure 4 shows an example of damage to building lots in Asahigaoka, Aoba Ward, which is approximately 4 km

5 Hill Gravelly terrace Terrace covered with volcanic ash soil Valley bottom lowland Alluvial fan Natural levee Back marsh Delta and coastal lowland Marine sand and gravel bars Sand dune Figure 3. Number of damage incidents to water distribution pipes with respect to the geomorphologic land classifications. Figure 4. Example of damage to building lots in the hilly residential area (Asahigaoka, Aoba Ward). north from JR Sendai Station. Because of the deformation of building lots, buried pipes were also affected in these areas. The damage incidents to water distribution pipes were concentrated in the hills where the deformation of building lots were caused. To perform the statistical analysis on the damage ratio of water distribution pipelines, the land utilization segmented mesh data provided as National Land Numerical Information [5] is employed in this study. The dataset is developed mainly based on topographical maps and satellite images, and the areas are classified into the 11 land use types. Figure 5 shows the land utilizations in Sendai City, Miyagi Prefecture as of In the figure, installation of water distribution pipes is also illustrated.

6 Figure 5. Land use classifications in Sendai City based on National Land Numerical Information [5] and installation of water distribution pipelines. Figure 6. Comparison of the damage ratios of water distribution pipes in the developed hilly areas and the other areas in Sendai City, Miyagi Prefecture. The damage ratios of water distribution pipes were obtained following the results shown in Figs. 2 and 5. First, the authors defined the hilly residential areas developed with cutting and leveling the hills and then filling the valleys, employing the JGEM and land use types. The areas where are classified as hills in Fig. 2 and as land for buildings in Fig. 5 were regarded as the developed hilly areas in this study. Then, the damage ratios of water distribution pipes were calculated for the developed hilly areas and the other flatlands, which are mainly lowlands and terraces. The results are shown in Fig. 6. The damage ratio of water distribution pipes in the developed hilly areas is approximately 3.5 times as large as that in the other flatlands. Comparison with the Fragility Functions for Water Distribution Pipes

7 Figure 7. Locations of seismic observation stations in Sendai City and their peak ground velocities during the 2011 off the Pacific coast of Tohoku Earthquake. Figure 8. Relationships between the peak ground velocity and the damage ratio of DIP and VP. The damage ratios of water distribution pipes were evaluated with respect to the peak ground velocity (PGV) during the 2011 off the Pacific coast of Tohoku Earthquake. To achieve the objective, the ground motion records obtained by K-NET [6], Tohoku University [7], and Tohoku Institute of Technology [8] are compiled in this study. Figure 7 shows the locations of seismic observation stations in Sendai City. The authors set the areas associated with the seismic observation stations based on topographical judgements as shown in Fig. 7. Figure 8 shows the relationships between the PGV and the damage ratio. The damage ratios were obtained for the DIP and VP, because most of damage incidents were found for these pipe materials. The damage ratio in the developed hilly areas and that in the flatlands were separately calculated. According to the figure, larger damage ratios are found in the developed hilly areas than in the flatlands. It shows approximately 2.5 times larger for DIP, and 2.3 times for VP. The overall scale factor of damage ratio is 2.4 for all pipe materials in Sendai City. To estimate the damage ratio of water distribution pipes (i.e., the number of damage incidents per kilometer of water pipe), Isoyama et al. [9] proposed the following formula.

8 Figure 9. Damage ratios of water distribution pipes in the flatlands in Sendai City and fragility functions proposed in the references [9-11]. Rm ( v) CpCdCgCl R( v) (1) where R m is the damage ratio, C p, C d, C g, and C l are correction coefficients for the pipe material, diameter, geological condition, and liquefaction occurrence, respectively, and v is the peak ground velocity (PGV). R(v) estimates the damage ratio for cast iron pipe (CIP) with a diameter of mm, and is proposed in different formulations [9-11]. Figure 9 compares the damage ratios of DIP and VP in Sendai City and other empirical fragility functions employing different R(v) proposed in the references [9-11]. In the figure, the damage ratios observed in the flatlands are compared. Since the damage ratios are small in Sendai City, the fragility function proposed in the reference [11], which gives the smallest estimations, shows a good agreement. To enhance earthquake security, various governmental organizations in Japan make predictions regarding earthquake-induced damages. The loss of lifeline system, e.g., disrupted water and gas supplies, electricity failure, etc. are estimated. Eq. (1) is commonly used to estimate the damage ratios of water distribution pipelines. The correction coefficient for geological condition, C g, is assigned according to the JEGM shown in Fig. 2. C g is set to be 0.4 for hills because they are generally regarded as hard soil, and the estimated damage ratio shows smaller values than the mean. However, the results of this study indicate that the damage ratios in the developed hilly areas show 2.4 times as large as those in the flatlands.

9 Figure 10. Comparisons of the eatimated damage ratios of water distribution pipes assigning a new correction coefficient for the developed hilly areas to be 2.4. The effects of developed hilly areas on damage ratios of water distribution pipes are shown in Fig. 10. In the figure, C g is set to be 2.4 to consider the effects of developed hilly areas, and 0.4 following the ordinal manner. R(v) proposed in the reference [11] is employed in Fig. 10. When C g is set to be 0.4, the fragility function gives underestimations. Hence, the damage ratios in the developed hilly areas should be properly estimated assigning their own correction coefficient. To that end, a technique to detect the hilly residential areas is required. This study proposes the use of the JEGM and National Land Numerical Information. Conclusions This study investigated the damage ratio of water distribution pipes in Sendai City, Miyagi Prefecture after the 2011 off the Pacific coast of Tohoku Earthquake. According to the locations of damage incidents to water distribution pipes, they are concentrated in the hilly residential areas. The damage to buried pipes was induced because of the deformation of building lots in the hilly residential areas developed with cutting and leveling the hills and then filling the valleys. Employing the ground motion records in Sendai City during the earthquake, the relationship between the damage ratio of water distribution pipes and the peak ground velocity was investigated. The damage ratios in the developed hilly areas show approximately 2.4 times as large as those in the flatlands, which are mainly lowlands and terraces. Based on the results, the authors introduced a new correction coefficient for the developed hilly areas, which can be applied to predict the damage ratio of water distribution pipes. In a future study, the effects of the developed hilly areas on the damage ratios should be investigated using another damage dataset to enhance the universality of the new correction coefficient. The accuracy to detect the hilly residential areas employing the Japan Engineering Geomorphologic Classification Map and National Land Numerical Information is to be examined. Acknowledgments

10 The authors would like to express their sincere gratitude to the Sendai City Waterworks Bureau for providing the dataset used in this study. References 1. Japan Water Works Association. Report of Damage to Water Facilities after the 2011 off the Pacific Coast of Tohoku Earthquake, (in Japanese) 2. Sendai City. Great East Japan Earthquake Damage, data_sendai/pdf/datasendai_14.pdf 3. Sendai City Waterworks Bureau. Record of restoration work, 06_bousai/jisin7.html (in Japanese) 4. Wakamatsu K. and Matsuoka M. Nationwide 7.5-Arc-Second Japan Engineering Geomorphologic Classification Map and Vs30 Zoning, Journal of Disaster Research 2013; 8(5): Ministry of Land, Infrastructure, Transport and Tourism. National land numerical information download service; 6. National Research Institute for Earth Science and Disaster Prevention. Strong-motion seismograph networks; 7. Motosaka M. Lessons of the 2011 great east Japan earthquake focused on characteristics of ground motions and building damage, Proceedings of the International Symposium on Engineering Lessons Learned from the 2011 Great East Japan Earthquake 2012; Tohoku Institute of Technology. Strong-motion records obtained by Small-Titan of Tohoku Institute of Technology during the 2011 great east Japan Earthquake 2011; /english/ 9. Isoyama R., Ishida E., Yune K. and Shirozu T. Seismic damage estimation procedure for water supply pipelines, Water Supply 2000; 18 (3): Tokyo Metropolitan Government. Disaster Prevention Information; /english/index.html 11. Maruyama Y. and Yamazaki F. Construction of fragility curve for water distribution pipes based on damage datasets from recent earthquakes in Japan, Proceedings of the 9th U.S. National and 10th Canadian Conference on Earthquake Engineering 2010; Paper No. 422: 10p.