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Influence of Lithosphere Rheology on Seismicity

The geological basis for this study. Geological map (left; modified after Asch 2005, BGR 2014) and 3-D URG model (right; Freymark et al., 2017).
Simplified geological map of the study area (left; modified after Asch, 2005, BGR, 2014) and calculated depth maps of the 450°C and 650°C isotherms as extracted from the 3D thermal model (Freymark et al. 2017). Overlain as grey circles are the hypocentre locations derived from different seismic catalogues.
Simplified geological map of the study area (left; modified after Asch, 2005, BGR, 2014) and integrated strength of the crust (middle) and entire lithosphere (right) as derived from the rheological model. Overlain as grey circles are the hypocentre locations derived from different seismic catalogues.
Modelled differential stress displayed along four vertical cross-sections the surficial extents of which are shown on the topographical and hypocentre map on the right. Dots indicate the depths and colour-coded magnitudes of hypocentres of seismic events projected onto the vertical sections (over horizontal distances of <5 km).

The Rhine Graben is one of the seismically most active areas in Germany and has been the target of many exploration studies aiming, for instance, at quantifying the distribution of its geothermal resources. However, a comprehensive study of the graben stability and its causative relationship to the natural seismicity has never been attempted. This is what has been addressed with this study that aims to assess how the lithospheric strength varies within the Rhine Graben and adjacent regions in response to the natural tectonic setting and the internal lithostructural and thermal configuration, and how those variations can be correlated to the recorded seismicity. Therefore, a first investigation of the present-day thermo-mechanical stability of the area is presented as based on a detailed 3D geological and thermal model.

The results indicate that there is a spatial correlation between the predicted graben-wide rheological configuration and both the deep thermal field and the configuration of the crystalline crust. By cross-plotting the modelled strength distribution with available seismicity catalogues, the results suggest that seismicity in the Upper Rhine Graben area is shallower and of lower intensity due to a hotter and weaker crust compared to its surrounding areas. In contrast, seismic energy release appears to occur at deeper levels and being of larger magnitudes east of the Upper Rhine Graben and in the Lower Rhine Graben to the north. The authors thus find that the regional 3D characteristics of the long-term strength of the lithosphere match the spatial distribution of seismicity, indicating that the mechanical stability of the area is primarily controlled by resolved strength variations. These results obtained from a data-driven and physics-based approach demonstrate the relevance of a proper quantification of the lithospheric rheological configuration and its spatial variability in response to its tectonic inheritance as an asset to interpret the pattern and distribution of seismicity observed in the area.

The study was performed in section 4.5 and could build on the previous projects IMAGE (EU) and Hessen3D 2.0 (BMWi) studying the thermal field of the region (Freymark et al. 2017; 2020).

Original study: Denis Anikiev, Mauro Cacace, Judith Bott, Maria Laura Gomez Dacal and Magdalena Scheck-Wenderoth. Influence of lithosphere rheology on seismicity in an intracontinental rift: the case of the Rhine Graben. Frontiers in Earth Science, 8, 492. https://doi.org/10.3389/feart.2020.592561

Related study: Freymark, Jessica; Sippel, Judith; Scheck-Wenderoth, Magdalena; Bär, Kristian; Stiller, Manfred; Fritsche, Johann-Gerhard; et al. (2017): The deep thermal field of the Upper Rhine Graben. Tectonophysics. https://doi.org/10.1016/j.tecto.2016.11.013

Related open access data: Freymark, Jessica; Bott, Judith; Scheck-Wenderoth, Magdalena; Bär, Kristian; Stiller, Manfred; Fritsche, Johann-Gerhard; Kracht, Matthias; Gomez Dacal, Maria Laura (2020): 3D-URG: 3D gravity constrained structural model of the Upper Rhine Graben. GFZ Data Services. https://doi.org/10.5880/GFZ.4.5.2020.004

Scientific contact (English/Russian):
Dr. Denis Anikiev 
Section 4.5 - Basin Modelling
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg
14473 Potsdam
phone: +49 331 288-2846
e-mail: denis.anikiev@gfz-potsdam.de

Scientific contact (English/Italian):
Dr. Mauro Cacace  
Section 4.5 - Basin Modelling
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg
14473 Potsdam
phone: +49 331 288-1783
e-mail: mauro.cacace@gfz-potsdam.de

Scientific contact (English/German):
Prof. Dr. Magdalena Scheck-Wenderoth 
RWTH Aachen University and GFZ-Potsdam
Section 4.5 – Basin Modelling
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg
14473 Potsdam
phone.: +49 331 288-1345
e-mail: magdalena.scheck@gfz-potsdam.de

Scientific contact (English/German):
Dr. Judith Bott
 
Section 4.5 - Basin Modelling
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg
14473 Potsdam
phone.: +49 331 288-1345
e-mail: judith.bott@gfz-potsdam.de

Scientific contact (English/Spanish):
Dr. Maria Laura Gomez Dacal  
Section 4.5 - Basin Modelling
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg
14473 Potsdam
e-mail: maria.laura.gomez.dacal@gfz-potsdam.de

Media contact:
Josef Zens  
Head of Public and Media Relations
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg
14473 Potsdam
phone: +49-331-288-1040 
e-mail: josef.zens@gfz-potsdam.de

 

 

 

 

 

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