抄録
Seismic motion amplification ratio corresponding to fundamental period, Gs1, is a very important factor used for evaluating site effects. In
this paper, a simple procedure for evaluating Gs1 of layered soil profiles is proposed. Firstly, a theoretical formula for Gs1 of a two-layer soil
profile on elastic bedrock, is developed. For a multi-layer soil profile, the multiple soil layers are approximately replaced by equivalent two
layers, then Gs1 of the multi-layer soil profile can be estimated by that of the equivalent two-layer soil profile on bedrock. To demonstrate
the validity of this development, Gs1 of 68 representative soil profiles are evaluated, it is shown that the results by the proposed procedure
agree well with those by the wave propagation method. Moreover, applying the proposed method for Gs1, free field response spectrum of
4 soil profiles are evaluated, and compared with the results by program SHAKE, good agreement between results by the two methods is
observed.
