Seismic microzonation; past, present and future

Abstract

The purpose of seismic microzonation has always been to estimate earthquake ground motion characteristics on the ground surface based on available geological, seismological and geotechnical data. During the early years, mostly geological data and observations from past earthquakes were used to prepare microzonation maps. In more recent years, regional earthquake hazard studies, geotechnical investigations, and site response analysis became more common. The uncertainties in source characteristics, soil profile, soil properties, and the characteristics of the building inventory can be considered as critical issues associated with these analyses. In the first stage, the probabilistic distribution of the related earthquake parameters on the ground surface may be determined considering all possible input acceleration time histories, site profiles, and dynamic soil properties. Generally, to account for the variability in earthquake source and path effects it is suggested to use more than 20 acceleration records compatible with the site-dependent earthquake hazard. Likewise, more or equal to 100 soil profiles generated by Monte Carlo simulations may be used to account for the variability of site conditions. Then the seismic microzonation in a specific area may be based on the probabilistic assessment of these factors in site response analysis. An attempt will be made to briefly review the past, present and possibilities for future studies on microzonation applications.