Uncertainty propagation of soil property in dynamic site response under different site conditions

It has been recognized that the soil profile and the associated parameters are usually not known with certainty in probabilistic seismic hazard analysis, however, little is known about the influence of site conditions on the propagation of uncertainty. This work aims to analyze and quantify the propagation of soil property uncertainties in site response analysis under different site conditions using a recently proposed DCZ constitutive model. Sensitivity analysis is performed to determine the most important parameter, which is regarded as a random variable in the subsequent uncertainty analysis. A Monte Carlo simulation procedure is applied to quantify the uncertainty propagation caused by the random variable. Detailed case studies involving multiple site conditions are presented to quantify the impacts of soil property variability under different site conditions in site responses. This study has found that variation in site response strongly depends on the shear wave velocity compared to other parameters. For softer soil, the PGA values at the ground surface show more dispersion (i.e., uncertainties) compared to stiffer soil. This indicates that for improving the accuracy of site response analysis and earthquake disaster prediction, it is necessary to operate probabilistic dynamic site response analysis rather than deterministic analysis, especially for soft soil.