Seeing More Clearly Beneath the Surface

Time-domain electromagnetic (TDEM) surveys are widely used to image the subsurface for groundwater mapping, raw material exploration, and environmental investigations.

During his PhD, Frederik Alexander Falk developed methods to improve the reliability of these subsurface images. Because direct observations are limited, interpretations rely on inversion methods that estimate geological structures from surface measurements. To handle large datasets, simplified assumptions are often used but can introduce misleading features into the results. Frederik investigated how these errors arise, how they can be identified, and how they can be reduced. He also studied how assumptions in probabilistic inversion affect what can be resolved from geophysical data.

The results provide a stronger foundation for producing reliable subsurface models while maintaining efficiency, supporting better decisions in applications such as the mapping of groundwater or raw materials.
The PhD study was completed at the Department of Geoscience, Faculty of Natural Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Thursday, 27 August 2026, at 12:00
Place: Building 1671, room 137, Auditorium at Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C
Title of PhD thesis: Towards More Reliable 1D Inversion of Time-Domain Electromagnetic Data: Diagnosing and Accounting for 3D Effects
Contact information: Frederik Alexander Falk, e-mail: frederikfalk@geo.au.dk, tel.: +45 51484616
Members of the assessment committee:
Professor Klaus Mosegaard, Niels Bohr Institute, University of Copenhagen, Denmark
Professor Niklas Linde, Institute of Earth Sciences, University of Lausanne, Switzerland
Professor Katrine Juul Andresen (chair), Department of Geoscience, Aarhus University, Denmark
Main supervisor: Associate Professor Thomas Mejer Hansen, Department of Geoscience, Aarhus University, Denmark
Co-supervisor: Professor Anders Vest Christiansen, Department of Geoscience, Aarhus University, Denmark
Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Natural Sciences/GSNS, Ny Munkegade 120, building 1521, 8000 Aarhus C