Using the HVSR to Study the Landslide Media Changes in Three Gorge Reservoir Area

Abstract The Huangtupo Linjiang Number 1 landslide (HTPLJ1) in the Three Gorges Reservoir area poses a significant geological hazard, influenced by periodic fluctuations in reservoir water level and rainfall. This study employs the horizontal-to-vertical spectral ratio (HVSR) method to investigate changes in the subsurface medium within the landslide body, using ambient noise data collected from five three-component nodal seismometers over a one-year observation period (2023). By analyzing temporal variations in peak frequencies and amplification factors, we identify distinct responses linked to shallow and deep sliding zones. Results reveal that reservoir water-level rise induces a notable decrease in peak frequencies and amplification factors for shallow sliding zones, attributed to reduced shear-wave velocities and impedance contrasts caused by increased pore-water pressure and effective stress weakening. In contrast, the deep sliding zone exhibits weaker hydrological sensitivity. Modal decomposition further delineates the dominant control of reservoir water-level fluctuations (low-frequency signals) compared with transient rainfall effects (high-frequency signals). Spatial heterogeneity in landslide response highlights the stronger influence of hydrological factors on the frontal zone relative to the rear. This study underscores HVSR as an effective tool for monitoring landslide stability dynamics and provides critical insights into hydromechanical coupling mechanisms governing landslide evolution in reservoir environments.