We have developed a management system on sharing for integrated geophysical and geological information databases to support researches on earthquake disaster prevention. The database consists of borehole information, geological data, geophysical data, and surface soil structures. Our target is to use the database on computer network. People can access the data sets on the underground database by using web browser like Internet Explorer.The management database system is based on the concept of establishing a portal site for individual agency to be responsible for its own data.

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In this paper, we overviewed a methodology for probabilistic fault displacement hazard analysis (PFDHA) proposed by Youngs in 2003 and we applied the method in Japan. While Youngs established the evaluation formula on the basis of the surface earthquake faults that appeared when the normal faults moved, we proposed the evaluation formula based on the surface earthquake faults generated by reverse and strike faults in Japan. As a result of model case analyses, the proposed evaluation formula gave a prospect for an applicability of the PFDHA in Japan and we described future tasks to be addressed.

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Ground-motion prediction equations are developed by regression analysis based on datasets of recorded ground-motion parameters at multiple stations during different earthquakes and in various source regions. The present probabilistic seismic hazard analysis applies the standard deviation of these equations to evaluate the hazard at a specific site (the ergodic assumption). The standard deviation has a strong influence on the results of probabilistic seismic hazard analysis at long return period. In the ground motion prediction equations, there is inevitably some mixing of epistemic uncertainty into the model of aleatory uncertainty. To improve the results of hazard analysis, it is important to quantify the aleatory uncertainty by removing the ergodic assumption. In this paper, the semivariogam procedure is adopted to separate of aleatory and epistemic uncertainty from the inter-event residuals in ground motion prediction equations for small-to-moderate earthquakes. The standard deviations of aleatory uncertainty in inter-event residuals are 0.315 for PGA and 0.354 for PGV. These values are about 40% smaller for PGA and about 20% smaller for PGV when compared the standard deviations of the whole data set.

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In this paper, we constructed a shallow underground structure model of Kochi city for the area of 10.5 km in east-west by 5.5 km in south-north direction with a resolution of 125 m. By compiling the geological information opened by the Committee of Kochi Geo-Hazard Evaluation (2011), we constructed a multi-layered model embedded over the engineering bedrock with the S-wave velocity of 700 m/s. Based on our newly developed model, dispersion characteristics of theoretical surface waves at two sites were calculated and agreed well with observed ones derived from our microtremor-array experiments. The predominant periods along two north-south lines calculated from our model were coincident with the previous observational data shown by Mori at al. (2001).We also conducted a seismic response analysis using the synthesized ground motion from the Central Disaster Management Council of Japan (2003) as the input motion of basement of the developed subsurface structural model. We found that the area where relatively high seismic intensity was predicted was well corresponding to the severely damaged area during the 1946 Nankai Earthquake.

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