The role of Regional Geology as key aspect in the planning of large subsurface infrastructures

The Einstein-Telescope (ET), a next-generation gravitational wave-detector, is a triangular shape underground facility with 10 kilometres long arms to be constructed at a depth of 200-300 meters below surface. A potential location is the Meuse-Rhine Euroregion. The success of such mega-project requires a comprehensive understanding of regional geology in terms of lithology, lithological variations and dominant structures. A solid regional geology study, combining literature review, reconnaissance study, surface and subsurface mapping, sample collection, geophysical data collection, and remote sensing methods to identify the rock units and structures present, is part of assessing the feasibility of the area. The lithology consists of soft Upper Cretaceous sediments resting unconformable on Silesian, Dinantian and Famennian units. The Dinantian carbonates and the Famennian sandstones are the preferred target units for the cavern construction. A major goal is to understand the spatial distribution of the different rock units that may be encountered during construction of caverns and tunnel. Structurally, the region shows a complex pattern of NE- SW striking Variscan folds and thrusts and (N)NW –(S)SE striking faults linked to the Lower Rhine Embayment. Changes in the lithology due to folds and thrust are important in terms of tunnel planning. The (N)NW – (S)SE structures provide pathways for fluids and are potentially seismic active and hence may affect the construction and the operation of the ET severely. Understanding the regional geology allows for optimization of the location and orientation of the ET infrastructure and identifies the potential impacts during construction and operation of the ET.