Movements within the Earth's crust that have occurred in the recent past or are occurring now are described as neotectonic processes.
Movements within the Earth’s crust that took place in the recent past or that are currently taking place are referred to as neotectonic processes. Faults are the particular focus of geoscientific investigations. At faults, geological units are shifted vertically and horizontally. This means that they provide us with information concerning geological development and also define areas where movements could currently occur.
Postglacial uplift and salt intrusion
In previously glaciated regions, such as northern Germany, post-glacial rise of land masses caused by the melting ice sheets also play a role. This is known as the Glacial Isostatic Adjustment (GIA). If GIA and faults coincide, this can lead to movements at faults and hence induce earthquakes. LIAG is also investigating interactions of this kind in Lower Saxony, for example. Salt intrusion is a further possible trigger for changes in the stress field, particularly in northern Germany. Understanding neotectonic processes and the associated hazards is a challenge. Faults are often overlaid by sediments, meaning that the outcrops are sparse. This is where we need geophysical methods to image the faults spatially and obtain indirect information about the temporality of fault activities. At LIAG, we respond to these challenges by using reflection seismic, dating and modelling, amongst other methods. Geophysical investigations are yielding ever more data that substantiates previously unknown tectonic movements in the distant past.
High-resolution reflection seismic measurements using the measurement technology developed at LIAG return detailed images of fault geometry and strata structures that have been shifted by the faults. The use of shear waves also allows us to deduce the elastic moduli, in particular the shear modulus. This parameter describes the elastic deformation behaviour of the subsurface and is of great importance for its characterisation. The institute is involved in projects investigating concealed near-surface faults around the world. In New Zealand e.g., we are working with the Institute for Geological and Nuclear Science to explore concealed faults in the Whakatāne district, around 30 kilometres away from the Edgecumbe Fault that was reactivated by a severe earthquake in 1987.
Seismic images show the current state of faults. Dating provides us with important information about the chronology of past earthquakes that triggered movements at faults. LIAG develops luminescence and ESR dating methods to be able to directly date earthquakes for the last 2.6 million years using fault gouges. This is important information that promotes the understanding of geological evolution and provides qualitative indications of future movements. For example, LIAG performed luminescence dating for the Northern Harz Boundary Fault in Lower Saxony. At the Atotsugawa fault in Japan, we showed that the methods are useful for comparing the relative activity of faults. LIAG researchers are currently dating a wide range of faults in Pakistan, Austria, Slovenia and other countries. The European Alps are a new area of focus: We successfully acquired two projects to date main faults in the Alps as part of the DFG priority programme Mountain Building Process in Four Dimensions (4D-MB).