Utilizing Ambient Seismic Noise in Hydrogeology Studies

Ambient seismic noise has become a valuable tool in seismology, playing a crucial role in environmental seismic studies. This research explores the Horizontal-to-Vertical Spectral Ratio (HVSR) method's applicability to groundwater studies in two distinct cases: the Río de la Plata Coastal Plain, Argentina, and the Maltese archipelago.

In the hydrogeology of the Río de La Plata region, partially interconnected coastal porous aquifers within sedimentary formations prevail. Employing HVSR analysis on ambient seismic noise reveals two prominent peaks. The low-frequency peak is associated with the sediment-basement interface, while the higher frequency is linked to a shallower stratigraphic discontinuity. Temporal analysis unveils cyclical patterns in mean frequency and amplitude, correlating with estuarine levels. This suggests a compelling connection between variations in subsurface mechanical properties and tidal dynamics, supported by phreatic and piezometric measurements.

In Malta, with primary aquifers developed on limestone rocks, a distinct HVSR peak related to a claystone-limestone stratigraphic boundary is observed. Preliminary results indicate changes in HVSR shape associated with seasonal variations in groundwater. This study underscores the potential of ambient seismic noise analysis as a non-invasive and cost-effective approach to studying aquifers and gaining insights into groundwater dynamics.

This work has been supported by DEMUWA project which is financed by the Malta Council for Science and Technology through the Space Research Fund (Building Capacity in the Downstream Earth Observation Sector) a program supported by the European Space Agency. Funds were also made available through the IPAS (Internationalisation Partnership Awards Scheme) funded by the Malta Council for Science and Technology.