抄録
Not a few reinforced concrete buildings were heavily damaged in Tokachi-oki earthquake in 1968, Japan. But the ratio of heavily damaged to total buildings was fairly small in spite of their structural strength being thought to be nearly coordinate. At the beginning of this investigation, a sort of resonance phenomenon between the predominant period of ground and the natural period of building was thought to be one of the most important element which caused to structural damages. As the results of our investigations, it cannot but be concluded that the damages could not be explained only from the resonance phenomenon between structure and ground. A more important factor which is the frequency density of predominant peak included in an original ground motion was found through the investigating works, and the factor is called frequency selectivity in this paper. From many observed data obtained from micro-tremor and after shocks, it was proved that the frequency selectivity had a close relation with the earthquake damages of building in Hachinohe and its suburbs.
