Construction of Disaster Damage Index based on Knowledge-based Classification of Landform and Surface Ground

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The knowledge about the condition of the ground is a crucial factor that controls damage due to natural disaster. However, to collect information on the ground condition over a wide area is not an easy task. In order to solve this issue, we have looked at the fact that the condition of the ground is closely related to the landform. This research aims to establish a method of constructing a surface soil model over a wide area based on the landform.By choosing Chiba area, which is located east of Tokyo, a number of soil investigation data have been collected and organized as a database that was constructed on a GIS. Landform classification was also added to this database. Based on this database, a number of standard soil profiles that are typical to classified landform have been constructed. Dynamic characteristics such as amplification factors have then been computed from these soil profiles. Based on this result in conjunction with other existing data, an earthquake damage prediction has been performed. It was found from this study, landform has a significant influence on the prediction.Dynamic properties of the ground near the edge of diluvual terrace were also studied based on microtremor and seismic motion observations. It was found that spectral intensities and maximum accelerations are larger at the top of the slope than in the central part of terrace and at the foot of the slope. It was also found that the predominant frequency changes to higher frequencies in accordance with the distance from the top edge of the slope. Due to this strong influence of landform on the dynamic properties of the ground near the slope, 2-D or 3-D analyses may be necessary in this kind of area.