The reactivated intraplate Osning Lineament in northern Germany – Near-surface investigations using P- and SH-wave reflection seismics

Neotectonic movements can cause severe hazards and are scientifically and socially relevant for seismic hazard assessment and utilisation of the subsurface. In northern Germany, a presumed aseismic region, little is known about these processes and the associated structures, despite proven neotectonic activity, because many faults are hidden beneath sediments. To improve the knowledge of neotectonic activity, investigations of recently-active fault zones, like the Osning Lineament (OL) in North Rhine-Westphalia, are required.

To better understand the neotectonic evolution of the OL, we used a combined approach using high-resolution 2D P- and SH-wave reflection seismics to investigate four different sites at the Bielefeld-Segment of the OL. Overall, we acquired three P-wave profiles with which we were able to image the underground down to 700 to 800m depth, and four SH-wave profiles that imaged the subsurface down to 100m depth.

The seismic profiles show good results with respect to mapping the fault inventory. In the Cretaceous, Triassic, and Quaternary several, previously unknown, northward-dipping thrust faults are evident, which have upthrusted the formations toward the south. The faults form fault splays that developed due to the propagation of the OL into the footwall. The slow shear-wave velocities, especially in the Quaternary, allow for very high-resolution imaging of the subsurface and the identified faults are evidence for neotectonic activity. More to the south, we also observed some southward-dipping normal faults, which are interpreted as basin faults of the Münsterland Basin dipping towards the basin center.