Characterization and quantification of active faulting in the Roer valley rift system based on high precision digital elevation models

Abstract : The Roer valley rift system (RVRS) is located in the northern prolongation of the upper Rhine Graben. During the Cenozoic, the evolution of the RVRS was influenced by two different rift systems situated in the North and in the South (the North Sea rift system and the West European rift system, respectively). During the last decades, moderate seismicity revealed the continuous activity of the graben border faults (the Peel Boundary fault zone -PBFZ- and the Feldbiss fault zone-FFZ-). We use a high precision digital elevation model (DEM) to characterize and quantify the present-day deformation along these faults. The fault pattern shows similarity to a strike-slip structure. However, analysis of the DEM reveals that the Recent to Quaternary formations and landforms affected by the fault activity are only vertically offset. This suggests a pure normal faulting mode for the main border faults and a direction of extension perpendicular to the graben (i.e., NE–SW). Quantification of the offset dated markers allows the determination of the displacement rates along the fault segments. In the southeastern part of the RVRS, the vertical displacement rates inferred for the FFZ and the southeastern PBFZ range between 55 and 65 mm/ky and around 65 mm/ky, respectively. In contrast, the displacement rates determined for the northwestern segment of the PBFZ are around 200 mm/ky. We explain these differences between the northwestern and southeastern parts of the RVRS by the large-scale geometry of the graben, the RVRS being symmetric in the south-east and asymmetric (half-graben) in the north-west. The deformation is accommodated by two border faults (FFZ and the south-eastern part of the PBFZ) in the south-east and by only one fault in the north-west (the north-western segment of the PBFZ). In addition, the thickness of the Neogene main depocentre in the northwestern half of the RVRS indicates a larger amount of extension in this part of the graben than in the south-east. The combination of the graben geometry and the amount of extension can explain the differences in the displacement rate.
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Quaternary Science Reviews, Elsevier, 2005, 24, pp.457-474. 〈10.1016/j.quascirev.2003.11.009〉
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Laurent Michon, R. T. Van Balen. Characterization and quantification of active faulting in the Roer valley rift system based on high precision digital elevation models. Quaternary Science Reviews, Elsevier, 2005, 24, pp.457-474. 〈10.1016/j.quascirev.2003.11.009〉. 〈hal-01382030〉

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