Tsunami Focusing Along a Valley of Linearly Varying Width and its Effect on Building

Indonesia is frequently hit by tectonic earthquakes and tsunamis of various scales. The giant tsunami in Aceh at the end of 2004 was one of the largest tsunami in the world that resulted in an estimated loss of U.S. $ 10 billion. The calamity definitely confirmed that understanding of tsunami loading on buildings is the most important to mitigate future tsunami disaster. The main purpose of this research is to determine the tsunami forces on building located in an area surrounded by two narrowing cliffs / walls. The simulations were performed using a flume measuring 24m long by 1.45m width and 1.5m high equipped with tsunami wave generator of dam-break system type at Universitas Gadjah Mada. The result of the research indicated that the effect of the vertical cliffs on tsunami forces depends on the wave height and the position of the building relative to the valley. The closer the distance of the building to the end of the valley, the greater was the force of tsunami wave. The theoretical approach agree with the experimental data at certain extend. Keywords: tsunami force, focusing, valley, model, simulation