Coastal inundation of southern Taiwan induced by tsunami originating from manila trench

The primary objective of this study is to develop a preliminary tsunami early-warning system, which aims to mitigate the tsunami-generated inundation and possible catastrophe in southern Taiwan. The unsteady, straight, and continuous fault zone adjacent to southwestern Taiwan heightens the stress for potentially powerful temblor of magnitude 8.0 or larger (Lin, 2008, and Anat Ruangrassamee, 2009). A submarine quake of magnitude 8.7 at Manila Trench was assumed and given to the model proposed by Dao et al.(2009), which predicted the generated fault scale and initial tsunami wave scale. Tsunami wave propagation around Taiwan was simulated numerically to discuss the potential coastal inundation. COMCOT model which developed by Cornell University was used to simulate the generated tsunami wave propagation. Multi-layer nested grid system was applied in the model. The grid resolution is coarser for far offshore area,3.42km×3.42km and is finer near coastal area, 54m×54m .Mid-layer grid resolution is 216m×216m. Wave transformation due to shallow effect, focusing in a bay beach and diffraction at downstream side of an island were revealed in the model reults. Detail discussions on the tsunami wave characteristics affected by local topography will be given in the full paper. The potential areas at risk of tsunami intrusion and flood inundation in southern Taiwan were predicted by the numerical model. At southeastern coast of Taiwan, rarely tsunami inundation was found due to the steep slope of seabed topography which not only reflected back incoming tsunami wave but reduced the shoaling effect of tsunami. However, the low-lying southwestern coast of Taiwan existed a high potential of coastal flood by reason of the shoaling effect of tsunami and accompanied with increasing wave height. For the purpose of further investigation on high potential tsunamiinundated sites, the time-series data of surface elevation at many interested sites were examed. Maanshan nuclear power plant, located in Houbihu, Kenting, in the vicinity of Nanwan lowland suffered from the first wave, 3.5m and short response time, 21-minute. The coastal area between Tainan and Pintung is relatively mild slope and moreover, the coastline oriented toward the incoming direction of tsunami wave. So, those area exposed directly to high-energy tsunami wave which caused large inundation area especially at Tainan and Qijin, Kaohsiung. At Taiana city, the severe damage propably caused by the upstream propagation of tsunami wave and followed by flooding along Zeng- Wen River. On the other hand, Qijin was submerged due to its low land elevation and high tsunami wave run-up.