In this study, we propose a procedure for constructing seismic vulnerability functions of elevated railway based on case histories of elevated railway structures damaged by past earthquakes. Damage rates at each seismic intensity level in the 1995 Southern Hyogo Earthquake and the 2011 Great East Japan Earthquake are calculated. The results indicate that (1) slight damages on structures of elevated railways appear from the JMA seismic intensity 5- and heavy damages appear from the JMA seismic intensity 6-, (2) heavy damage rates in the 2011 Great East Japan Earthquake are lower than that in the 1995 Southern Hyogo Earthquake, (3) slight damage rates in the 2011 Great East Earthquake are higher than that in the 1995 Southern Hyogo Earthquake, (4) total damage rates in the 2011 Great East Japan Earthquake are comparable with that in the 1995 Southern Hyogo Earthquake.

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An evaluation method of horizontal strong motions was examined based on strong-to-weak motion (S/W) spectral ratio at the ground surface. The inverse analysis of S/W spectral ratio is intended to account for the soil nonlinearity (dynamic deformation characteristics) of the target layer, namely, is to determine the shear stiffness (S-wave velocity) and damping factor corresponding to shear strain. Then, the horizontal strong motions are evaluated using the nonlinear ground model obtained by the inverse analysis. In order to confirm the applicability of the evaluation method, we have performed numerical experiments using a simulated ground model, and have further evaluated the horizontal strong motions on the engineering bedrock with S-wave velocity about 500m/s at 300m depth of the Quaternary ground by using the observed S/W spectral ratio. As a result, the estimated strong motions satisfactorily reproduced the observed records on the engineering bedrock and showed high accuracy.

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In light of the 2011 off the Pacific coast of Tohoku Earthquake (Tohoku Earthquake) Tsunami and the accident at the Fukushima Dai-ichi nuclear power plant, it is necessary to improve the probabilistic tsunami hazard assessment for tsunami risk evaluation of nuclear power plants in consideration of the possibility that the tsunami in the future exceeds the largest magnitude in the past. After the Tohoku Earthquake Tsunami, the new modeling methods for scenario tsunami are proposed based on the above concept. In this study, one of the new modeling methods is applied to the inter-plate earthquake tsunami located on the Japan Trench and the Chishima Trench, and the effects of dealing with uncertainties in tsunami evaluation on the results of the probabilistic tsunami hazard assessment are shown by comparing it with those using the conventional modeling method based on the maximum in the past.

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