| dc.description.abstract | The violent rain induced by the 2009 Morakot typhoon, accumulated over 2000mm precipitation within 4days, caused widespread landslides in the southern Taiwan. The landslide at Hsiaolin village, unfortunately, completely destroyed the village and caused over 400 deaths. This is an extremely rare case worth detailed study. It is known that the village was covered twice. First, the massive landslide from the top hill overlaid the village at the riverside and blocked the river to form a barrier lake. Next, the lake dam collapsed and the debris covered the village area again. This forms a natural deposit situation having several layers, one above the other. In this study, we used the traditional refraction method to explore the layered deposition structure and to estimate the depths of building been buried.
Basing on the traditional Plus-Minus method, we developed a new analysis technique to resolve the multiple-layered structure for the refraction data. After identifying different segments of travel time curves for different layers, we design on inversion algorithm to reconstruct the travel time curve from these incomplete segments. Several constraints are emplaced to confine the travel-time curve trend, which may lead to a reasonable distribution. A complete travel time curve including the observed and estimated parts is thus formed, which is then used to calculate the underground refraction layer.
The results are as follows:
1) The original ground surface is buried under 3~5m depths at the village area The covered layer, i.e., the first layer, is composed of new landslide materials with the P velocity 400m/sec.
2) The second layer represents the original deposit layer above the basement. The thickness is between 15 and 20m, which may accumulate the old landslide debris. The P velocity is around 1500m/sec.
3) The basement surface is relatively irregular, which is marked by ancient river cuts as well as some weak zones. The basement has P velocity as 3000m/sec and consists of mudstones and sandstones.
4) The profile at the original river position possesses three layers above the basement. This agrees with the two times covering of the landslide material and the river debris.
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