The methodology -oriented scientific work undertaken by the department covers four different topics. The fundamental geophysical work undertaken by the department is covered by the topics "Development of seismic sources and surveying technologies", and "Gravimetry & Magnetics". This is complemented by the topic "Structural analysis and deformation modelling" which deals with structural-geological approaches for the interpretation of geophysical data − primarily seismic data. The fourth topic, "Georisks", is a field of research activity that is more thematic and is becoming increasingly important.
The "Seismic, Gravimetry, and Magnetic" department provides its expertise to all three of LIAG's focal research fields, whereby the topic-oriented work of the main research activities primarily profit from the methodological development activities of the department - which are also motivated by this involvement. Advances in multi-component seismic in particular enables to pursue new approaches in the exploration and characterisation of geothermal reservoirs for instance, as well as the high-resolution description of sedimentary deposits. The latter is just as important for the evaluation and protection of groundwater systems as it is for understanding climate-controlled or geogenically affected changes to landscapes. In addition, structural and deformation modelling is indispensable for a deeper understanding of geological system changes, and in particular of fault systems. For instance, they provide important insights into the structural and physical properties of georeservoirs.
In accordance with our objective of using high-resolution seismic methods to study in detail the structures and processes taking place in anthropogenically-affected underground rock formations, we use state-of-the-art seismic methods and in particular reflection seismic surveys. These are based on the underground propagation of artificially-generated elastic waves which change when they encounter boundary surfaces, and therefore enable the identification of structures such as horizon boundaries and faults.
The quality of the seismic survey therefore depends on using appropriate sources and surveying technologies to match the target of the investigation and the surveying conditions. Important aspects here include the strength of the source, the repeatability of the signal, the coupling to the underground formations, as well as the bandwidth and frequency content of the signal. Another important role is played by the logistics requirements, such as the practicability out in the field. We therefore develop sources and surveying technologies accordingly. LIAG gained many years of experience in the development of seismic sources for shallow seismic surveying, and is an international leader in this field.
The recording and interpretation of anomalies in the Earth's gravity field (gravimetry) and the Earth's magnetic field (magnetics) and/or their change over time is a fundamental applied geophysical activity. Department S1 carries out gravimetric and magnetic surveys to explore tectonic and geological structures, as well as for a better understanding of the processes involved. The physically relevant geoparameters are the density and the magnetisability (susceptibility, remnant magnetism) of the rocks. These methods are therefore a major supplementary technique to reflection seismic surveys with respect to the structural and physical characterisation of underground rock formations.
Structures in the Earth's crust can be explored from the surface by seismic methods. We use reflection seismic measurements − mostly in the form of seismic lines − to visualise specific geological structures and thus to make the structure and properties of underground geological formations visible for the first time and to analyse them. The horizons and faults interpreted from the seismic lines are also used in fault and deformation modelling to interpret the sub-seismic deformation history of the area being investigated. To find out whether the mechanisms and magnitudes determined and predicted in this way are realistic, we also do fieldwork to investigate faults directly and therefore to verify our hypotheses.
Georisks per se encompass all types of natural risks that threaten human habitats. Major well-known events include volcanism, earthquakes, storms and floods. Moreover, there are also less extreme phenomena that are also hazardous; these include mass movements, surface subsidence or uplift, as well as contamination (natural or anthropogenically caused or exacerbated). Our work focuses on georisks of this kind at the geotechnical scale. Methodological developments in other areas of activity are profitably combined here to assist this socially-relevant topic.