Investigating Soil Saturation Changes through Geophysical Data

The water cycle impacts geophysical signals, influencing our ability to monitor subsurface hydrology. At the Membach geophysical station in Belgium, we integrate gravity and ambient seismic noise data to study hydrological variations and develop a numerical hydrological model at a local scale. Our findings reveal that gravity observations at Membach station exhibit gradual changes, reaching a peak at ± 2-day after rainfall, reflecting subsurface water redistribution and storage processes. Concurrently, increased soil saturation corresponds with a decrease in HVSR (Horizontal-to-Vertical Spectral Ratio), indicating reduced stiffness and changes in seismic wave propagation. Furthermore, relative velocity changes (dv/v) show frequency-dependent time delays, with deeper layers exhibiting slower responses compared to shallower regions. These results highlight the dynamic relationship between rainfall, soil saturation, and geophysical responses, providing new insights into critical zone processes. By combining gravimetry and ambient seismic noise, we address challenges in studying deep and complex subsurface zones, where traditional hydrological methods often fall short. This approach not only enhances our understanding of subsurface hydrology but also improves water resource management and critical zone studies. The integration of geophysical methods offers a comprehensive framework for monitoring hydrological dynamics, advancing our ability to interpret geophysical signals influenced by the water cycle and providing a valuable tool for managing environmental and climatic impacts on subsurface water storage.