3D site response analysis

Site response analysis (SRA) is a critical component of geotechnical earthquake engineering, used to evaluate how local soil conditions modify seismic waves from bedrock to the ground surface. While traditional one-dimensional (1D) SRA methods provide valuable insights into vertical wave propagation, they simplify real conditions by neglecting the full range of seismic input components that can influence ground motion characteristics. This study presents a comparative analysis of multidirectional site response modeling for a series of well-instrumented downhole arrays in Anchorage, Alaska, United States, and the Zeytinburnu soil profile in Istanbul, Türkiye, subjected to various recorded earthquake events. By incorporating all three earthquake components (East–West, North–South, and Vertical) into a multidirectional SRA framework, the research aims to achieve more accurate estimates of site amplification. The results reveal distinct differences in modeled ground motions between three-dimensional and one-dimensional analyses at various soil depths, demonstrating the enhanced reliability offered by a multidirectional approach. These findings underscore the necessity of employing more comprehensive modeling strategies in regions with high seismicity. Furthermore, an optimization study was performed as part of the research to reduce uncertainties in input parameters, with a primary focus on shear wave velocity (Vs) and the stiffness modulus derived from it. Comparisons between unoptimized and optimized models show that the optimized profile more closely aligns with recorded ground motions. This improvement highlights the framework's ability to refine key soil properties, ultimately resulting in enhanced predictive accuracy at the ground surface.