Effect of Variabilities in Motion Characteristics and Bedrock Depth on Seismic Ground Response Assessment

The half-space depth significantly affects the seismic ground response by influencing a particular site's amplification and attenuation characteristics. Hence, the present study focuses on assessing the impact of half-space depth on seismic ground response using nonlinear 1-D numerical analysis. The properties of Nevada sand and calibrated nonlinear parameters available in the literature have been used for constructing the numerical models. This study uses a wide range of variations in the motion characteristics, that is, spectral accelerations, frequency contents, and duration characteristics, to assess the seismic ground response for different depths of half-space. An interesting finding of the study is that the effect of bedrock depth on seismic ground response modification differs when assessed at different depths. The response at shallow depth (at 5 m) shows less de-amplification in energy content for large bedrock depth. At the same time, the de-amplification in energy content is almost similar for all the models at 25 m depth. On the contrary, the modification in frequency content is always higher for larger bedrock depth. A regression equation has been proposed to predict the response Arias Intensity (AI) depending on input energy content, half-space depth, and response measurement depth.