Nonlinear seismic response analysis of selected sites in Chennai

Surface geology and geotechnical characteristics of soil deposits have a paramount importance on ground shaking which alters the ground motion parameters. Ground response analyses are used to predict the surface motions for the development of design response spectra to calculate the earthquake induced forces developed on the structures and evaluation of liquefaction hazards. Chennai, the India's fourth largest metropolitan city with wide variation in geological strata brings the special attention of soil amplification during earthquake. In this paper, the influence of nonlinearity on site response analysis are summarized and evaluated by considering the three typical sites in Chennai city. The first part of study describes the evaluation of seismic hazard at bed rock level using deterministic approach. Next, the site characterization has been carried out by conducting Multichannel analysis of surface wave (MASW) tests. The local site effect has been studied for rocky, sandy and clayey soil deposits by conducting nonlinear ground response analysis using Flac3D. To study the effect of nonlinearity on ground motion, the equivalent linear analysis has been carried out using SHAKE and compared with nonlinear ground response analysis.