Abstract
In the discussion of a dynamic behavior of ground motion during earthquake, an analytical model as multireflection system or lumped mass system has been considered. Howeverr the snslytical model representations of surface layer would be accompanied by various difficulties, because the composition of actual soil layers and the mechanism of wave propagation would be too complex to represent by simply idealized model. The proper dynamic characteristics of surface layer can be obtained from observation of actual earthquake records, even if the analytical structure of the soil ground could not be made clear. In this study, a dynamic behavior during earthquake are argued by using the resultant characteristics of surface layer obtained from observations in their exact conditions, and the analytical structure of which is kept from taking into account. Owing to the recent progress of high speed computer, the technique of frequency analysis of earthquake motion has remarkably advanced. This study is an original proposal using high speed computer which has made it possible to carry out this method of thought. This method would be more practical than the past analytical methods because a characteristics of surface layer is given in such a form as it is. In this paper part 1, only the peculiar characteristics of earthquake motions were discussed which were required as a preliminary work to introduce this method.
