SITE RESPONSE ANALYSIS FOR DEEP DEPOSITS IN ALMATY

Abstract

This study presents a detailed site response analysis for deep soil deposits in Almaty, a seismically active region located in southern Kazakhstan. The primary objective of the research is to evaluate the influence of local soil conditions on ground motion amplification and the resulting surface response spectrum for deep soil deposits. Given Almaty’s complex geological setting, characterized by thick alluvial deposits, the analysis considers soil profiles with bedrock depths reaching up to 500 meters. Both Equivalent Linear (EL) and Nonlinear (NL) methods were employed using DEEPSOIL software to assess the dynamic behavior of the soil under strong seismic shaking. A suite of input ground motions was selected from the NGA-West2 database and spectrally matched to the target response spectra from Kazakhstani seismic design code. The results highlight significant amplification at specific period ranges, with the NL analysis showing higher surface accelerations for deeper deposits at longer periods due to nonlinear soil behavior, while the EL struggling to accurately model nonlinearity in deep soil layers under strong seismic loads. The findings provide critical insights into the seismic response of Almaty's deep soil layers, contributing to improved seismic hazard assessment and design of earthquake-resilient structures in the city. The study emphasizes the necessity of considering nonlinear soil behavior in regions with deep sedimentary basins to achieve more accurate seismic design parameters.