Title: Does regional geology help to assess earthquake hazard in continental interiors?

Tim Hahn1, Jonas Kley1, Diethelm Kaiser2, Thomas Spies2

1Geoscience Center, University of Göttingen, Germany; 2Unit ‚Engineering Seismology‘, Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany

Event: GeoKarlsruhe 2021

Date: 2021

DOI: 10.48380/dggv-51cr-m188

Earthquake hazard assessment is crucial for different planning tasks, including the search for a German nuclear waste repository. Germany is located in an intraplate setting with a low level of seismicity and the seismically active faults are incompletely known. To solve this problem, seismotectonic regions (SR) of assumed uniform seismicity can be defined and used as a basis to define seismic area sources to be used in seismic hazard analyses. We have elaborated a new concept for a transparent implementation of geological data. Our basic assumption is that the intensity of past geologic deformation controls the propensity of an area for renewed fault slip and earthquakes. Based on a compilation of published geological maps we analyzed the post-Variscan (<300 Ma) evolution of Germany´s fault network and created maps of geologic deformation intensity for six time slices. The time slice maps were superimposed to give a map of total deformation intensity. Regions of similar total geologic deformation intensity define SR. Comparison of these geology-based SR with recent seismicity (1000 years) shows good correlation in Cenozoic rifts (Lower Rhine, Upper Rhine, Eger grabens) and fair correlation of sparser seismicity in areas of strong and repeated Mesozoic deformation (particularly the “Mesozoic inversion belt” of central Germany). However, the prominent earthquake clusters of Brabant and the Swabian Jura occur in “stable” areas of little past deformation. We conclude that regional geology is a valuable source of information for seismotectonic regionalizations but should initially be analyzed separately from recent seismicity to avoid circular reasoning.

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