The Earth's interior remains hidden from us, but geophysics reveals its secrets. We use various methods, such as tomography, the measurement of gravity field variations or the change in distance between two fixed points, to explore the conditions and properties of the earth's crust.
This knowledge is crucial for the sustainable use of the subsurface, for example geothermal energy, the extraction of groundwater or the long-term and safe storage of gaseous and liquid substances such as hydrogen. Geophysics, as a scientific discipline at the interface between geosciences and physics, helps us to understand underground structures and to comprehend complex interrelationships in the subsurface.
Direct data on the deeper geological structure comes from boreholes and the material obtained from them, such as drill cores and cuttings. These can be used to determine the physical properties of rocks, such as permeability or thermal conductivity. Permeability, i.e. the permeability of rocks for liquids and gases, is an important parameter for understanding and recording the transport of energy and materials underground with the aid of simulation. Carrying out such simulations contributes to the scientific, technological and commercial use of the geological subsurface. Using core samples from a research borehole in Erfurt, we show how and why the rocks differ in their physical properties. However, as core data is rare and difficult to obtain, geophysics uses a variety of indirect measurement methods such as seismics, magnetics or gravimetry along profiles, which produce two- and three-dimensional models of the subsurface. As an example, we illustrate how subsurface models of the distribution of apparent electrical resistivity can be created using geoelectric measurements.
Another research focus at the Chair of General Geophysics is the investigation of changes in Earth and environmental parameters over long periods of time. At the Moxa Geodynamic Observatory, we use highly sensitive sensors to record the physical parameters of our Earth. Long-term measurement series are crucial to understanding the hidden processes deep below the Earth's surface. We show and explain long-term recordings of gravity field changes and crustal deformations, which we measure with superconducting gravimeters and laser strainmeters.
