Study on relationship between strong motions and structural damage observed during the West off Fukuoka Prefecture earthquake

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The West off Fukuoka Prefecture earthquake of Magnitude 7.0 occurred on March 20, 2005, which was the first earthquake of M7 class occurred near a big city since the devastating Hyogo-ken Nanbu earthquake of 1995. It is possible to obtain a lot of observational data that bears statistical analysis.We found:1) The seismic records of K-NET, KiK-net, the JMA network, and Fukuoka Prefecture network and others were collected and analyzed. We then delineate a heterogeneous distribution of slip (seismic moment) along the fault plane. We found a single asperity (a strong patch) located in the southeast of the hypocentet The strong motions radiated from this asperity were then amplified by thick Quaternary layers along the eastern side of the Kego fault2) The extensive building damage investigation was conducted in the central part of the city, and the damage statistics fur structural types, number of stories, and construction age has been grasped. We also investigated other types of damage, such as human injury, indoor damage, damage by liquefaction, and landslides. We found that the damage ratio of buildings is larger in the eastern side of the Kego fault, and that older buildings had more serious damage. We also hind that the indoor damage depends strongly on the number of stories. We should note that the damage occurs mostly in a non-structural components, which may contribute to prevent further damage in the major structural components.3) By comparing a presumed strung motions with observation damage, we investigated applicability of the nonlinear response analysis model. By using the model established by the damage during the Hyogo-ken Nanbu earthquake, we hind that calculated damage ratios are tuned out to be much more than the observed and so we may need to tune up our prediction model for a moderately severe input