The neotectonic evolution of the Osning Lineament derived from near-surface reflection seismic data

• Applicant: Dr. Sonja Wadas
• Subject Area: Geophysics ; Palaeontology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451088796

Neotectonic movements can cause severe hazards and are scientifically and socially relevant, e.g. for seismic hazard assessment, and utilisation of the subsurface for e.g. nuclear waste disposal sites and geothermal exploitation. In northern Germany, a presumed aseismic region, little is known about neotectonics because surface impressions are often missing; many faults are hidden beneath sediments.To improve the knowledge of the deformation related to and the timing of neotectonic activity, investigations of recently active fault zones, like the Osning Lineament (OL), are required. At the OL three historical earthquakes occurred in the past 400 years and the earthquake in 1612 damaged buildings in Bielefeld. The OL is a unique fault system compared to other faults in northern Germany. The faults of the OL reach the basement, whereas in the north of the Lower Saxony Basin most faults are decoupled from the basement by salt. Furthermore, the OL dips to the northeast and therefore the vector of the fault plane points towards the former iceload. Additionally, the OL had already been reactivated in the past, which might enhance further fault movement.An important step towards a comprehensive understanding of neotectonics at the OL, especially due to the limited availability of outcrops, is by using near-surface geophysical investigations, which have not been carried out at the OL as yet. It consists of a combined approach using high-resolution 2D P- and SH-wave reflection seismics. P-wave seismic alone can often not properly image near-surface impressions of faults due to poor shallow resolution, but this gap can be closed using SH-wave reflection seismics, which offers very high resolution, even at shallow depth. This will be combined with other geophysical methods, such as GPR, to investigate deformation features on sub-seismic scale, and sediment dating to derive the timing of fault movement.To be more precise, it needs to be determined how additional information on deformation features at depth complement the understanding of the interaction between glaciers and the pre-existing faults of the OL. This also includes the evaluation of the transferability of observations from sub-surface investigations to the surface, and if GPR provides additional benefit by closing the imaging gap between P-wave seismic, S-wave seismic, and outcrop scale. Furthermore, the local effect of fault geometry on stress distribution and fault reactivation, especially in the context of GIA needs to be investigated by, e.g. comparing the timing of fault reactivation and the known regional stress field with glacial events.The principal aims of this project are to reconstruct the neotectonic evolution of the OL (topics to covered: structural and physical analysis, historical- and paleo-earthquakes, and interaction of GIA and tectonic), and to evaluate how near-surface geophysics can contribute to neotectonic research.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Gerald Gabriel; Dr. Ulrich Polom; Dr. David Tanner