Saraswati, Anita ; Vanclooster, Marnik ; Lecocq, Thomas

Poster presented at 3rd OZCAR TERENO international conference - Paris, France on 2025-10-02

Abstract: The water cycle impacts geophysical signals, influencing our ability to monitor subsurface hydrology. Through a detailed hydrogeophysical investigation at the geodynamic station in Membach, Belgium, we aim to estimate hydrological variations in the surrounding area. Our focus is on integrating gravity and ambient seismic noise measurements to develop a hydrological numerical model at a local scale. Our findings reveal that gravity observations at Membach station exhibit gradual changes, reflecting subsurface water redistribution and storage processes in the soil. Concurrently, increased soil saturation corresponds with a decrease in HVSR (Horizontal-to-Vertical Spectral Ratio) at 50-70 Hz, indicating reduced stiffness and changes in seismic wave propagation in the critical zone. Furthermore, we also calculated the ambient noise cross-correlations of the records to obtain relative velocity changes (dv/v) in several frequency bands. For the higher frequency bands (30-60 Hz), we observe an immediate decrease in the dv/v changes after the rainfall, and a slight delay for the dv/v at 15-30 Hz frequency band. For dv/v on the lower frequency bands, the low-peak is situated days after the rainfall periods. These findings underscore the sensitivity of both gravimetric and seismic signals to rainfall-induced changes in soil saturation. The integration of these methods provides complementary insights into critical zone processes and hydrological behavior. 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.

Funding: FED-tWIN2022-prf-2022-041 - SEPARATOR#2/FED-tWIN2022-prf-2022-041 - SEPARATOR#2/FED-tWIN2022-prf-2022-041 - SEPARATOR#2