Deep Crustal, Intraplate Earthquakes in Northern Germany: Moho Detachment Tectonics and the Reactivation of a Fossil Megathrust
Abstract
Deep crustal earthquakes in continental interiors present a special challenge, because they are rare and their signals are often attenuated. We provide new evidence for deep crustal, intraplate earthquakes in northern Germany, a region usually regarded as low seismicity area. Between 2000-2018, seven earthquakes with magnitudes of ML 1.3 - 3.1, were detected at depths of 17.0 - 31.4 km. We consider that the inherited lithosphere structure is the first-order controlling factor of the distribution of these events and show that the faults of the Thor Suture, a fossil Ordovician megathrust are probably under reactivation. Five of the earthquakes group in the lower crust, near and below the Moho, which implies that the crust/mantle boundary in northern Germany acts as a structural discontinuity on which deformation localizes and that rupture processes are possible at that depth. These deep earthquakes, together with faults that reach depths of 20 km and more, underline the possibility of a tectonic detachment in northern Germany that might be located near the base of the lower crust. This detachment probably played a major role during a tectonic inversion phase that affected large parts of central Europe during the Late Cretaceous. This tectonic framework shows recent activity, as revealed by the deep earthquakes. Numerical simulation implies that stress changes due to glacial isostatic adjustment likely triggered these recent deep earthquakes and reactivated the megathrust. Furthermore, the modeling results imply that earthquakes are possible along optimally-oriented reverse faults, if the GIA stress has not yet been released.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T13F0241B
- Keywords:
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- 8110 Continental tectonics: general;
- TECTONOPHYSICS;
- 8122 Dynamics: gravity and tectonics;
- TECTONOPHYSICS;
- 8169 Sedimentary basin processes;
- TECTONOPHYSICS;
- 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS