Frequency-dependent seismic response to hydrological and bedload forcing in a glacier-fed stream

Proglacial streams that drain Alpine glaciers are characterized by variable hydrological forcing and highly intermittent sediment transport, making continuous monitoring of hydro-sedimentary processes necessary to understand their dynamics. Near-field seismic monitoring has recently been established as a valid non-invasive approach to studying river dynamics, since ground vibrations are sensitive to both flow turbulence and bedload transport.

In this study, we analyse the seismic response of a proglacial stream fed by the Rutor Glacier, the sixth-largest glacier in the Italian Alps, integrating passive seismic monitoring with hydrological and climatic observations. Three geophones were installed close to the active channel and continuously recorded ground vibrations at 200 Hz during the 2025 ablation season (June–September). The seismic power spectral density was analysed across different frequency bands. Water level was monitored using pressure sensors, while discharge was estimated using saline dilution tests, allowing the relationship between seismic signals and hydrological forcing to be investigated.

The preliminary results show marked diurnal fluctuations in water level driven by glacial melt. At low frequencies (5–15 Hz), seismic power increases predominantly linearly with water level, suggesting a dominant control by water flow turbulence. In contrast, at relatively high frequencies (30–40 Hz), the seismic response becomes nonlinear and exhibits a clear change in slope when a critical water level is exceeded, suggesting the activation and/or intensification of bedload transport superimposed on the hydraulic signal.

This study highlights the potential of environmental seismology as a non-invasive and continuous monitoring approach to investigate hydro-sedimentary dynamics in highly variable proglacial environments.