Site-Specific Ground Motion Studies for a Deep Soil Site Near Ahmedabad, Gujarat

Design ground motions are usually developed by one of two approaches: by performing site-specific analyses or from provisions of building codes. Although contemporary codes consider the site effects to an extent, they provide more conservative estimates. Hence, site-specific analysis, which involves both the seismic hazard analysis and ground response analysis, is a preferred approach to obtain design ground motions. This chapter presents a site-specific analysis for a site near Ahmedabad, Gujarat. The seismic hazard analysis was carried out by DSHA approach. The site is predominantly characterized by deep stiff sandy clay deposits. Extensive shear wave velocity measurement is used for site classification and ground response analysis. The ground response analysis was carried out by using two approaches: the equivalent linear approach using SHAKE2000 and the non-linear approach using FLAC2D. The deep-stiff-soil site is found to amplify the ground motion. The response from nonlinear analysis is found to be considerably higher than those obtained from the equivalent linear approach.