Seismic microzonation of Chennai City using fuzzy-probabilistic hazard and response analyses

Abstract

The critical structures and infrastructure facilities in densely populated and rapidly urbanising cities must be designed to withstand potential earthquake shaking without experiencing severe damage. This study aims to develop seismic microzonation maps and stipulates seismic design parameters for Chennai City, south India, by considering both aleatory and epistemic uncertainties. The fuzzy approach is employed in seismic hazard and ground response analyses to effectively manage the vagueness and imprecision of the input data and qualitative information of the study area. A systematic procedure for fuzzy-probabilistic seismic hazard analysis (FPSHA) and fuzzy ground response analysis (fuzzy-GRA) is developed as part of the study. A set of 11 spectrum-compatible recorded accelerograms consistent with the 475-year return period uniform hazard spectrum of Chennai City is obtained. These accelerograms are utilised as bedrock motions in the ground response analysis. The peak ground acceleration (PGA) values obtained at different depths from the hazard and ground response analyses are used to develop two-dimensional seismic microzonation maps for Chennai City. Additionally, maps of peak spectral accelerations and predominant site periods at the surface of the city area are established. The spatial variation of PGA at ground level for a 475-year return period in Chennai City ranges from 0.20 to 0.31g, with most places in the city exhibiting PGA values between 0.25 and 0.27g.