This study aims to estimate the spectral amplification factor of ground from the H/V spectral ratio of microtremors. The empirical amplification factor is calculated from the ratio of the response spectrum of the record to that on the engineering bedrock obtained from the attenuation relationship, for the K-NET and KiK-net observation sites. The empirical amplification factor is compared with the H/V spectral ratio of microtremors at different geomorphologic conditions. The relationships for estimation of the spectral amplification factor from the H/V spectral ratio are proposed for three geomorphologic groups. For the 2007 Niigata-ken-chuetsu-oki earthquake, the proposed method is applied. The estimated spectra show good agreements with the observed ones, and the effectiveness of the method is confirmed.

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Probabilistic hazard estimate through out Nepal considering historical earthquakes, intra plate slip and faults are done. As a typical case probabilistic spectra are plotted for Pokhara city. For the city, design earthquakes for three probabilities of exceedences are simulated which can be useful to design new structures and retrofit of existing structures.

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It is well known that landform has a strong influence on the dynamic properties of the ground. The objective of this study is to clarify the effect of a slope on the dynamic properties of diluvial terrace based on ground investigations, seismic motion observations and two dimensional finite element analyses, by choosing a target area that has a landform typical to the southern Kanto plain. Three sets of finite element analysis model have been constructed; the first one is based on the detailed ground investigation and has a weak soil at the slope between the terrace and the lowland, the second one does not have a weak soil, and the third one consists of a homogeneous soil. Through this study, the followings were found:(1) Due to the weak soil at the slope, amplification becomes very large, but the area of influence is relatively small.(2) Amplification due to ground irregularity is relatively small, but the area of influence is fairly large.(3) The mechanism of this large area of influence due to irregularity can be explained by the generation of surface waves at the slope.

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After a large-scale earthquake disaster, we must be able to determine the routes of vehicles for rescue operations. For this purpose, we must rapidly collect road information at an early stage over a wide area. To achieve this purpose, aerial images will be useful, because they enable us to rapidly collect information over a wide area and are unaffected by the disaster. We propose a method of extracting road blockage areas in an urban area using aerial images obtained after an earthquake disaster and a digital map. In this method, using edge and color information, we extract damaged areas of roads and areas of collapsed buildings. Then, we correctly extract road blockage areas using the positional relations between the damaged areas of roads and the areas of collapsed buildings. We developed software on the computer, based on the proposed method, and we analyzed actual aerial images and evaluated the effectiveness of our method.

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We carried out damage investigation around the seismic stations where high JMA seismic intensity scales were recorded in the 2007 Niigata-ken-chuetsu-oki Earthquake. Among the seismic stations with 6+ JMA seismic intensity scales we found many heavily damaged wooden houses around K-NET Kashiwazaki, Kashiwazaki- Chuomachi Shindokei, but we did not find heavy damage around the Nagaokashi-Oguni and Iizunacho- Imokawa Shindokei. We did not find heavy damage around the seismic stations with 6- JMA seismic intensity scales. We investigated the correspondence of strong ground motions with damage to buildings. We found that 2-2.5 sec. dominated in the records of K-NET Kashiwazaki, Kashiwazaki-Chuomachi Shindokei with heavy damage and large 1-2 sec. responses that brought about severe damage to buildings. On the contrast, in the case of the records of the Nagaokashi-Oguni and Iizunacho-Imokawa Shindokei with 6+JMA seismic intensity scales and no heavy damage, short period below 1 sec. dominated and the 1-2 sec. responses were small.

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