Imaging large-scale geological structures using Deep ERT: a case study on the Booze Val-Dieu block in Belgium

Abstract

The geophysical investigation of geologic structures is an essential prerequisite for the preparatory phase of large subsurface construction projects like caverns or tunnels and to study structural geology. This type of investigation is crucial to guide boreholes for relevant ground truth, knowledge of the local geology, or to adjust the position of underground constructions.Typical approaches to image large structures are seismic reflection surveys or Airborne Electromagnetic surveys (AEM). However, seismic surveys might fail due to an absorbing soft top layer or steeply inclined layers. AEM surveys generally are poorly adapted to applications in urbanized areas. To overcome these issues, another method for large-scale subsurface imaging is the application of Deep Electrical Resistivity Tomography (Deep ERT), a recent approach where employing separated injection and measurement systems allows for large injection dipoles that retrieve information from depth.We conducted a Deep ERT campaign in the framework of the E-TEST project for the investigation for a suitable location for the Einstein Telescope, a gravitational wave observatory consisting of a set of subsurface laser interferometers in a triangular shape at a depth around 300 m. Here, we present the results from a 2D Deep ERT survey in Val Dieu, Belgium with a total length and maximum injection dipoles of 7,5 km and a total of 14040 measured datapoints. We show the challenges during preparation, performance and data processing and discuss its capability in imaging large and deep geological structures.

Authors 9

1. Yannick Forth

   University of Liège

   Affiliation as printed

   University of Liège, Urban and Environmental Engineering, Liège, Belgium

2. Hadrien Michel corresponding

   University of Liège

   Affiliation as printed

   University of Liège, Urban and Environmental Engineering, Liège, Belgium

3. David Caterina

   University of Liège

   Affiliation as printed

   University of Liège, Urban and Environmental Engineering, Liège, Belgium

4. Joost Hase corresponding

   University of Bonn

   Affiliation as printed

   University of Bonn, Institute of Geosciences, Geophysics Section, Bonn, Germany

5. Andreas Kemna

   University of Bonn

   Affiliation as printed

   University of Bonn, Institute of Geosciences, Geophysics Section, Bonn, Germany

6. Nils Chudalla Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Computational Geoscience, Geothermics and Reservoir Geophysics (CGGR), Aachen, Germany

7. Florian Wellmann corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Computational Geoscience, Geothermics and Reservoir Geophysics (CGGR), Aachen, Germany

8. Bjorn Vink

   National Institute for Subatomic Physics

   Affiliation as printed

   Nikhef, Projectbureau ET-NGF, Amsterdam, Netherlands

9. Frédéric Nguyen corresponding

   University of Liège

   Affiliation as printed

   University of Liège, Urban and Environmental Engineering, Liège, Belgium