Influence of elevated topography and overlying soil layers on seismic ground motion characteristics

To investigate the combined effects of elevated topography and overlying soil layers on local seismic site response as well as the mechanisms of earthquake-induced hazards, a series of representative numerical site models with varying topographic heights and soil conditions were developed using the finite element method, based on post-earthquake field investigations. The Fourier amplitude spectral ratio and Fourier amplitude spectral difference were utilized to evaluate the seismic response characteristics for different site configurations. The results indicate that resonance amplification, superposition effects, and peak frequency coupling are the primary mechanisms through which topographic features and overlying soil conditions jointly influence local seismic ground motion characteristics. The relative contributions of these factors to seismic amplification are critical in determining the severity of earthquake-induced engineering damage. Furthermore, the coupling of peak amplification frequencies resulting from both topographic and overlying soil effects is identified as a significant mechanism contributing to seismic hazards. Notably, when the amplification frequencies induced by topography and overlying soils coincide in frequency and are comparable in amplitude, the coupling effect becomes most pronounced. This results in a marked enhancement of seismic response, potentially exposing structures within the site to the most unfavorable conditions for seismic performance. This study provides valuable insights into seismic design under complex site conditions and contributes to the development of more effective earthquake-resistant strategies for engineering applications.