Estimation of the fixed-base dynamic characteristics of buildings using microtremor observation has difficulty when the upper input force, e.g. wind force and pressure on the underground wall, exists. In this study, an effective method for estimating the fixed-base transfer function of the buildings having large horizontal stiffness between soil and foundation is investigated considering the influence of the upper input force as bias errors. Those errors in the estimation depend on the model parameters and the upper input force parameters. For most cases, however, the dominant frequency of the obtained transfer function well approximates the natural frequency of the system without any influence of the upper input force.
