Identifying large vulnerable water reservoirs using passive seismic monitoring

Seismic waves capture important insights into subsurface behavior. We introduce an adapted coda-wave interferometry approach to monitor the spatial variability of semi-daily periodic seismic velocity changes on a regional scale, applied to data collected across South and Central Europe. Our results reveal a broad spatial correlation between seismic velocity changes and air pressure fluctuations, suggesting that air pressure is the dominant driving force. Specifically, air pressure fluctuations modulate saturation levels within the capillary zone through the dynamic interplay between fluid and gaseous phases, producing significant seismic velocity changes. The mechanism explains the large variations observed in regions with high connectivity between the surface and saturated zone. We associate this enhanced interaction with the high vulnerability of shallow water resources. We propose inspecting semi-daily periodic seismic velocity changes as a new tool for gaining a regional view of water reservoir vulnerability.