Monitoring spatio-temporal water redistribution in the subsurface with seismic methods

Lara Blazevic
Monitoring spatio-temporal water redistribution in the subsurface with seismic methods

Sujet : Distribution spatio-temporelle de la teneur en eau en proche surface à partir de méthodes sismiques

Title: Monitoring spatio-temporal water redistribution in the subsurface with seismic methods

 Abstract: The characterization and monitoring of subsurface water systems are fundamental to groundwater resources conservation and management. To this end, hydrogeophysics provides a suite of non-invasive methods to study the shallow subsurface environment and the processes occurring therein over multiple scales. Time-lapse hydrogeophysical applications are notably useful to monitor water dynamics and follow temporal variations in water content. Largely dominated by electrical and electromagnetic methods, these applications are being increasingly explored with seismic methods. The seismic signal is dependent on the mechanical properties of the medium which are in turn affected by changes in water content. Consequently, seismic responses are also influenced by hydrological properties and state variables. Nonetheless, complexities in describing the mechanical behavior of partially saturated shallow materials have limited the quantitative characterization of the subsurface and associated water dynamics by means of seismic methods. Here we investigate the evolution of seismic responses with varying water content in time-lapse field contexts, analyzing both data and inverted parameters, and compare the resulting trends with established petrophysical relationships. We show that seismic time-lapse inversions of P-wave refraction data and corresponding changes in wave propagation velocity enable the recognition of preferential water flow paths in the subsurface, highlighting the potential of seismic methods to monitor hydrological processes and unsaturated flow. Overall, qualitative agreements between seismic velocity trends and theoretical petrophysical relationships still eclipse accurate quantitative estimations of water content from inverted seismic parameters. We anticipate further time-lapse seismic field studies to help bridge the gap between qualitative and quantitative observations. In the wake of the recent advancements in seismic equipment and techniques, appropriate field-scale petrophysical relationships will play an important role in the development of seismic methods for hydrological applications.

Keywords: Hydrogeophysics, seismic data, monitoring, petrophysics, vadose zone

This project has been carried out in the framework of the ENIGMA ITN (European training Network for In situ imaGing of dynaMic processes in heterogeneous subsurfAce environments


Ludovic Bodet - Damien Jougnot - Laurent Longuevergne (Géosciences Rennes UMR 6118)
Ecole Doctorale: 
Date de Soutenance: 
sep 2020
Date de début: 
oct 2017