Abstract: Adopting Monte Carlo simulation technique, a method for describing the variability of site transfer function (STF) with respect to the variability of site characteristic parameters is proposed. Two Kik-Net seismic strong-motion stations, which were installed on hard ground (FKSH12) and soft site (FKSH14) in Japan, were selected and corresponding probability site models were established. 50 site soil profiles were randomly generated for hard ground and soft site via Monte Carlo simulation; and then the STFs were calculated as well their standard deviations, respectively. The standard deviations of STFs and the site characteristic frequencies were discussed in three cases, i.e. varying subsoil thicknesses (case I), varying subsoil shear wave velocities (case II), and varying subsoil thickness and shear wave velocities (case III). The results show that: the standard deviations of site characteristic frequencies of hard ground is overall larger than those of soft site; the standard deviation of site characteristic frequency of hard ground is the smallest in case I, followed by case II, while in case III the standard deviation of site characteristic frequency is the largest; the standard deviations of soft site characteristic frequencies in case I and case II are comparative but weakly smaller than that in case III; the standard deviations of STFs in case III for soft site and hard ground are slightly larger than those in case I and case II; but the standard deviations in the three cases are not considerably different; the standard deviations of STF are fairly large in the vicinity of site predominant frequencies with peak values corresponding to peak values of relevant mean STF.

Key words: site transfer function, site characteristic parameter, Monte Carlo, variability