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[P-08] Cascading effects of tsunami disasters

*Anawat Suppasri Suppasri¹, Miwako Kitamura¹, Syamsidik Syamsidik², Abdul Muhari³, Fumihiko Imamura¹, David Alexander⁴ (1. Tohoku University, 2. Syiah Kuala University , 3. Ministry of Marine Affairs and Fisheries, Indonesia, 4. University College London)

Keywords:Cascading disasters, Tsunamis, Disaster risk reduction

In 2015, cascading disasters is defined as “cascading effect or dynamic impact of a physical event or the development of an initial technological or human subsystem that result in physical, social or economic disruption”. In 2018, a magnitude scale for cascading disasters was qualitatively defined to six levels, Level 0 [Simple or major incident], Level 1 [Major incident with limited complexity], Level 2 [Major incident or small disaster with some complex consequences], Level 3 [Disaster with complex consequences], Level 4 [Disaster with substantially complex consequences] and Level 5 [Catastrophe with overwhelmingly complex consequences]. However, the proposed magnitude scale is still lacking 1) quantitative criteria/definition for each magnitude level and 2) detailed analysis of cause, effect and escalation point of each magnitude scale. Tsunami disaster was selected as the first case study applying perspective of the cascading disasters in our study. Hazard parameters as well as consequences from recently occurred several tsunamis in Japan and other countries were reviewed and classified to each magnitude scale. As examples, the 2016 Fukushima tsunami was classified as Level 2 as the consequences were only limited to offshore area, no long-term interruption of infrastructure and no casualty as well as damage to buildings. The 2018 Palu tsunami is a good example for Level 4 as the tsunami itself was the consequence of earthquake, submarine landslide and liquefaction. Damage to ports causing interruption of shipping (both domestic and international) and local business/tourism and damage to a prison causing riot, escaping of prisoners which increased criminal rates and reduced social security were examples of escalation point of this event. The 2011 Great East Japan tsunami was selected as a case study to analyse the process of Level 5 in detail. Results from this proposal can be used for future planning and management against tsunamis in the future.