*Corresponding author. Tel.: +6681 735 0409 Email address: piyafo@kku.ac.th doi: 10.14456/kkuenj.2016.148 KKU ENGINEERING JOURNAL 2016;43(S3):431-435 Research Article KKU Engineering Journal https://www.tci-thaijo.org/index.php/kkuenj/index Tsunami risk assessment of the 2004 Indian Ocean tsunami in Kamala beach Phuket Piyawat Foytong* 1) and Anat Ruangrassamee 2) 1) Sustainable Infrastructure Research and Development Center, Department of Civil Engineering, Faculty of Engineering, Khon Kaen University, Khon Kaen 40002, Thailand. 2) Department of Civil Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand. Received April 2016 Accepted June 2016 Abstract The December 26th, 2004 Indian Ocean tsunami caused damage to many buildings and killed many people in Indian Ocean countries. Regarding the 2011 Tohoku Japan tsunami, the devastating tsunami ravaged the eastern coast of Japan. It is important to mitigate the damage by tsunamis in the future. These events emphasize the need of tsunami risk assessment for evacuation planning, estimation of loss and estimating residential damage from tsunami hazard. The residential damage in Kamala Beach, Phuket is evaluated by the proposed tsunami fragility curves. The proposed tsunami fragility curves are considered only reinforced-concrete buildings and classified into two types: one-story buildings and buildings taller than one story. Building inventory is surveyed and classified into 5 zones. The tsunami inundation heights in each zone are averaged from the observed damage data. The results of evaluated buildings damage are compared with actual observed damage. Most one-story buildings are damaged in primary members and for buildings taller than one story are damaged in secondary members only. The damage probability for observed buildings of each area agrees well with the evaluated damage of buildings. Keywords: Tsunami risk assessment, Fragility curves, Reinforced-concrete building 1. Introduction The 26 December 2004 Indian Ocean tsunami caused serious damage to a large number of buildings and killed many people in the Indian Ocean countries including the western coastal regions of Southern Thailand. Regarding the 2011 Tohoku Japan tsunami, an unexpected earthquake with a magnitude of 9.0 occurred near the eastern coast of Honshu, Japan on March 11, 2011. This devastating tsunami ravaged the eastern coast of Japan. Approximately 20,000 people were killed and 830,000 construction buildings were damaged. To prevent and reduce structural damage in the future, there is a need to understand the behaviors of buildings under tsunami loading. The damage from these events emphasize the need of tsunami risk assessment for evacuation planning, estimation of loss and estimating residential damage from tsunami hazard. The primary components in risk assessment are hazard, fragility curves and structural inventory. This study evaluates the residential damage in Kamala Beach, Phuket, Thailand in the December 26th, 2004 Indian Ocean tsunami. The residential damage is evaluated by the proposed tsunami fragility curves [1]. Finally, the results of evaluated damage of buildings are compared with actual observed damage. 2. Damage of buildings at Kamala beach, Phuket, Thailand From the observed database [2], the December 26th, 2004 tsunami caused the inundation height of about 3 m. which caused damage to many buildings in Kamala beach Phuket, Thailand as shown in Figure 1. Building damage data is distinguished into 5 zones. Zones are branched following the local road. Table 1 shows the number of damaged buildings in each zone for one-story buildings and buildings taller than one story. There are 62 observed damaged buildings in this area. 9 buildings suffered no damage, 31 buildings were damaged in secondary members, 19 buildings were damaged in primary members and 3 buildings collapsed. The distribution of 4 damage levels in this area for reinforced-concrete buildings is shown as Figure 2. From the observed damaged buildings, the average inundation heights and the probability of damage levels 0, 1, 2 and 3, which are average overall damage of buildings, of each zone for one-story buildings and buildings taller than one story are shown in Table 2. Most damage for one-story buildings is the damage level 2 and most damage for buildings taller than one story is the damage level 1. For zones 4 and 5, the probability of damage for one-story buildings is 100% because there are a small number of buildings in these zones.