Time-Lapse Seismic and Electrical Monitoring of the Vadose Zone during a Controlled Infiltration Experiment at the Ploemeur Hydrological Observatory, France

Abstract

The vadose zone is the main host of surface and subsurface water exchange and has important implications for ecosystems functioning, climate sciences, geotechnical engineering, and water availability issues. Geophysics provides a means for investigating the subsurface in a non-invasive way and at larger spatial scales than conventional hydrological sensors. Time-lapse hydrogeophysical applications are especially useful for monitoring flow and water content dynamics. Largely dominated by electrical and electromagnetic methods, such applications increasingly rely on seismic methods as a complementary approach to describe the structure and behavior of the vadose zone. To further explore the applicability of active seismics to retrieve quantitative information about dynamic processes in near-surface time-lapse settings, we designed a controlled water infiltration experiment at the Ploemeur Hydrological Observatory (France) during which successive periods of infiltration were followed by surface-based seismic and electrical resistivity acquisitions. Water content was monitored throughout the experiment by means of sensors at different depths to relate the derived seismic and electrical properties to water saturation changes. We observe comparable trends in the electrical and seismic responses during the experiment, highlighting the utility of the seismic method to monitor hydrological processes and unsaturated flow. Moreover, petrophysical relationships seem promising in providing quantitative results.

Predicting the frequency-dependent effective excess charge density: A new upscaling approach for seismoelectric modeling

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Near-surface real-time seismic imaging using parsimonious interferometry

“…We selected a dry sand dune that could be considered as a vadose zone, which is an important challenge for hydrological characterization 13 , 14 . Hydrological characterization can be accomplished by using geophysical techniques to image the subsurface hydrogeological structures at appropriate scales 14 . In addition, time-lapse geophysical methods have proven useful for monitoring flow and water content dynamics 15 .…”

Assessing the Impact of Fractured Zones Imaged by ERT on Groundwater Model Prediction: A Case Study in a Chalk Aquifer in Voort (Belgium)

“…ERT is suitable for many hydrogeological applications (Binley et al, 2015) such as locating cavities and fractures or estimating layer thicknesses and detecting interfaces between layers (e.g., Guérin, 2005;Al-Tarazi et al, 2006;Guérin et al, 2009;Robert et al, 2011;Van Hoorde et al, 2017). It has also been used together with tracer experiments to identify preferential flow paths and solute transport processes along fractures (e.g., Robert et al, 2012) or image infiltrating processes in the unsaturated zone (Lesparre et al, 2017;Claes et al, 2019;Blazevic et al, 2020).…”