Large-scale 3D structural geological models in alpine regions: impact and societal utilities.

The Swiss Geological Survey (SGS) is the competence centre for the subsurface and georesources of the Swiss Confederation. Between 2024 and 2030, the SGS is leading the Swiss Alps 3D (SA3D) project, which consists of eight modelling and research projects involving several universities. The aim is to develop a consistent, large-scale underground 3D geological model of the main contacts and structures of the Swiss Alps. This model will serve as a regional framework for future higher resolution 3D models, enabling a wide range of applications in infrastructure planning, groundwater studies, natural hazard assessment, education and research. Furthermore, the development of a large-scale, consistent model will promote the establishment of a collaborative scientific community in the field of Alpine geology and 3D geological modelling.

SA3D has been preceded by a four-year pilot study (2019 - 2023), which resulted in an explicit 3D geological model of the Aar Massif (Central Alps). The study highlights the importance and value of utilising 3D geological models when investigating complex geological systems, such as an orogen. In this contribution, we present the results of this pilot study to demonstrate the potential of the large-scale 3D geological models constructed in SA3D for a wide range of applications.

In fact, modelling 3D network of structures and lithostratigraphic contacts of mountain ranges provide strategic insights into the still largely unexplored subsurface of these regions. This is essential for a sustainable infrastructure development and regional assessment of primary resources. Furthermore, the characterization of large-scale 3D fault patterns is relevant for understanding the effects of tectonic preconditioning on the distribution of natural hazards and meteoric water penetration and upflow in orogens. This may have important implications for regional-scale hazards mitigation and for the exploitation of thermal anomalies in orogenic geothermal systems through realistic numerical simulations, as well as for the evaluation of the influence of meteoric water on the seismicity of regional faults.