Since it is well known that the vibration characteristics such as the eigenperiod and the damping ratio of buildings are dependent on the amplitude of vibration. In this paper, these characteristics of the horizontal first mode, based on the seismic observation records obtained from the low and middle raised RC and SRC buildings, are studied. These characteristics are evaluated corresponding to the 2 amplitude levels, the small earthquake level and the middle earthquake level. The observation data are analyzed using the ARX model. The effects of the experience of large earthquakes and aging for each amplitude level are investigated.
