Based on transfer function

the three procedures of spectral characteristics analysis

seismic response time-frequency estimation

and the spectral correction for input ground motion are proposed. Discussion and verification for these procedures are made based on the seismic analysis of Baihetan hydropower station underground power houses. The results indicate that the seismic input-output relation for underground engineering can be clearly expressed by transfer function. The results are well consistent with the conclusion made by the other methods. Generally the response of floor may be stronger than that of crown

and may contain different main frequency bands. However the response of floor is smaller than that of crown in the band of 3-4 Hz. The method of seismic response time-frequency estimation made with transfer function and based on white noise calculation is feasible. It is believed that this procedure can greatly reduce the time-consuming computation

and makes it possible to grasp the main seismic response characteristics of target project with limited amount of computation. Moreover

the correction of spectral characteristics for the input ground motion to correspond with the spectral reference points of carven bottom or the water level of valley can guarantee the reasonable mechanism of the input ground motion.