The system identification method proposed and discussed by the authors to estimate the dynamic characteristics of a building under an imaginary fixed base condition was applied to a partly embedded nuclear reactor building. Although this building has a large soil-structure interaction (SSI) effect, and the proposed method is essentially made for systems without embedment, the aplicability of the method has already been checked and confirmed using an analytical model in a previous paper. Data on microtremors data from excitation tests. and data from earthquakes of an actual building are studied in this paper. Effects made by put-of-plane deformation of the base mat, the sharing ratio between the sealed and inner walls of the excitor force, and the number of frame averaging needed tbr reliable spectral analysis are also studied.
