Frequency-Based Comparative Analysis of Ground Vibration Spectra at Multiple Monitoring Locations Under Soil-Rock Impact Conditions

Ground vibration characteristics provide valuable information regarding dynamic soil behavior and potential instability in riverbank and near-surface geological environments. This study presents a frequency-based comparative analysis of vibration signals measured at nine monitoring locations subjected to soil–rock impact excitation. Three-directional vibration signals (transverse, vertical, and longitudinal) were recorded and processed using bandpass filtering and Fast Fourier Transform (FFT)-based spectral analysis. The measured signals were segmented and normalized to evaluate temporal and spatial variations in dominant frequency behavior. Comparative spectral analyses revealed significant differences among monitoring locations, particularly in the low-frequency range associated with soil softening and reduced stiffness conditions. The results demonstrate that dominant frequency shifts and spectral broadening can effectively identify spatial heterogeneity and localized dynamic instability zones. The proposed methodology provides a simple and practical framework for vibration-based assessment of soil degradation and instability in riverbank environments.