Space-time monitoring of groundwater fluctuations with passive seismic interferometry

Historic levels of drought, globally, call for sustainable freshwater management. Under pressing demand is a refined understanding of the structures and dynamics of groundwater systems. Here we present an unconventional, cost-effective approach to aquifer monitoring using seismograph arrays. Employing advanced seismic interferometry techniques, we calculate the space-time evolution of relative changes in seismic velocity, as a measure of hydrological properties. During 2000-2020 in basins near Los Angeles, seismic velocity variations match groundwater tables measured in wells and surface deformations inferred from satellite sensing, but the seismological approach adds temporal and depth resolutions for deep structures and processes. Maps of long-term seismic velocity changes reveal distinct patterns (decline or recovery) of groundwater storage in basins that are adjacent but adjudicated to water districts conducting different pumping practices. This pilot application bridges the gap between seismology and hydrology, and shows the promise of leveraging seismometers worldwide to provide 4D characterizations of groundwater and other near-surface systems. Characterization of groundwater systems is important for sustainable freshwater management. Here, the authors map the distribution of groundwater storage changes at several hundred meters below the metropolitan Los Angeles during 2000-2020, by developing a cost-effective method using ambient ground vibrations recorded by seismometers.

Automated summary

Researchers have developed a cost-effective method using seismograph arrays to monitor aquifers and measure hydrological changes through seismic velocity variations. The study reveals that seismic velocity changes in the groundwater systems near Los Angeles are consistent with groundwater levels measured in wells and surface deformations detected by satellite sensing, but provide higher temporal and depth resolution. This approach can identify patterns of groundwater storage changes under different pumping practices and provide valuable information for sustainable freshwater management.