Utilisation of the shallow underground

Today there is a great deal of interest in the structure of the shallow subsurface. Around half of Switzerland’s drinking water comes from loose rock formations near the earth’s surface, and these formations are also a major source of mineral resources (sand and gravel quarry). Furthermore, heat energy is extracted from the shallow underground throughout the country with the aid of geothermal probes. The uppermost rock layers also form the foundations for housing development and the construction of transport routes.

Basic data

In order to produce 3D models of the shallow underground, uniformly structured data have to be available. Since so much use is made of the shallow underground, a great deal of data are available relating to its structure. The numerous recordings of drilling operations are the most important data source. Borehole data reveal the sequence of the geological layers at a specific location. Other data sources include the results of geophysical surveys (seismic, gravimetric, geo-electric, electromagnetic, etc.) and geological cross-sections. Thanks to the already available comprehensive geological data from the surface, it is possible to obtain an overview of the geological conditions throughout the entire country.

3D geological models and their uncertainties

Unconsolidated rock formations are more heterogeneously structured than the underlying bedrock formations. In addition, the distribution of the existing data is highly varied. In order to be able to develop 3D geological models with the required degree of validity, it is also necessary to model the quality and the uncertainty of the data. The Swiss Geological Survey takes this into account when developing 3D geological models, so that the most reliable basic geological data and 3D models can be available in the future.