Recent developments in site response analysis and microzonation

The basic issues in the site response analysis are the uncertainties in source characteristics, soil profile, soil properties, and site response analysis procedure. The probability distribution of the related peak and spectral accelerations on the ground surface may be determined considering all possible input acceleration time histories, site profiles, and dynamic soil properties. One option to account for the variability in earthquake source and path effects may be to consider using large number of acceleration records compatible with the site-dependent earthquake hazard partially based on hazard deaggregation for the investigated site. Likewise, stochastic soil profiles generated via Monte Carlo simulations can be used to account for the site condition variability. The second important issue is the selection of microzonation parameters. The selection of microzonation parameters such as Cumulative Absolute Velocity (CAV) and Housner Intensity (HI) is emphasized for their stronger empirical correlation with structural damage. The adopted methodology advances traditional site response analysis by integrating frequency- and stress-dependent soil behavior models to achieve a more accurate numerical model. It also highlights the need for representative time histories with known exceedance probabilities. Even though the selected representative acceleration time histories may be scaled with respect to probabilistic acceleration spectrum or peak ground acceleration obtained based on probabilistic site response analysis; the probability of the selected acceleration time histories is not known. The only possible option is to estimate probabilistic acceleration time histories with predetermined exceedance probabilities to enhance fully probabilistic site response analysis.