Probabilistic seismic hazard analysis considering nonlinear site effect

A modified method is proposed for the probabilistic seismic hazard analysis considering nonlinear site effect. A case study is presented to show the h azard curves that consider the nonlinearity of the soil layers at Gilroy #2 . Source, parameters and an earthquake occurrence model are assigned to the Caleveras fault, which is assumed the dominant seismic source to the site. A relationship between ground surface and bedrock accelerations at the sit e is established by recordings from three earthquake events using the progr am NONLI3, which calculates the nonlinear responses of the soil layers to s trong motions. Various values of standard errors of the estimated surface P GA, given the bedrock motions, are assumed to perform a sensitivity analysi s. An alternative nonlinear relation is included in the case study. In addi tion to the nonlinear models, a linear-response model is also performed usi ng the same soil profile at Gilroy #2. The results demonstrate that the haz ard curves an sensitive to the standard error of the estimated surface PGA values at the site. The hazard curve may be severely distorted if the soil condition of a nonlinear site is treated inadequately. The alternative nonl inear model obtained empirically from regression analysis and the linear re sponse model are both unsuitable for the hazard assessment considering nonl inear site effect.