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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/nhess-2017-126
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
15 May 2017
Review status
This discussion paper is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria) for seismic hazard assessment
Esther Hintersberger1, Kurt Decker1, Johanna Lomax2,3, and Christopher Lüthgens2 1Department of Geodynamics and Sedimentology, University of Vienna, 1090 Vienna, Austria
2Institute of Applied Geology, University of Natural Resources and Life Sciences (BOKU), 1190 Vienna, Austria
3Department of Geography, Justus Liebig University Gießen, 35390 Giessen, Germany
Abstract. Including faults into seismic hazard assessment depends strongly on their level of seismic activity. Intraplate regions are characterized by low seismicity, so that the evaluation of existing earthquake catalogues does not necessarily reveal all active faults that contribute to seismic hazard. In the Vienna Basin (Austria), moderate historical seismicity (Imax/Mmax = 8/5.2) concentrates along the left-lateral strike-slip Vienna Basin Transfer Fault (VBTF). In contrast, several normal faults branching out of the VBTF show neither historical nor instrumental earthquake records, although geomorphological data indicate Quaternary displacement along those faults. Here, we present a palaeoseismological dataset of three trenches crossing one of these splay faults, the Markgrafneusiedl Fault (MF), in order to evaluate the seismic potential of the fault. Comparing the observations of the different trenches, we found evidence for 5–6 major surface-breaking earthquakes during the last 120 ka, with the youngest event occurring at around ~ 14 ka before present. The inferred surface displacements lead to magnitude estimates ranging between M = 6.2 ± 0.3 and M = 6.8 ± 0.1. Data can be interpreted by two possible event lines, with event line 1 showing more regular recurrence intervals of about 20–25 ka between the earthquakes with M ≥ 6.5, and event line 2 indicating that such earthquakes cluster in two time intervals in the last 120 ka. Event line 2 appears more plausible. Trench observations also show that structural and sedimentological records of strong earthquakes with small surface offset have only low conservation potential. Vertical slip rates of 0.03–0.04 mm/a derived from the trenches compare well to geomorphically derived slip rates of 0.015–0.085 mm/a. Magnitude estimates from fault dimensions suggest that the largest earthquakes observed in the trenches activated the entire fault surface of the MF including the basal detachment that links the normal fault with the VBTF. The most important implications of these paleoseismological results for seismic hazard assessment are that: (1) The MF needs to be considered as a seismic source irrespective of the fact that it did not release historical earthquakes. (2) The maximum credible earthquakes in the Vienna Basin should be considered to be about M = 7.0. (3) The MF is kinematically and geologically equivalent to a number of other splay faults of the VBTF. It must be assumed that these faults are potential sources of large earthquakes as well. The frequency of strong earthquakes near Vienna is therefore expected to be significantly higher than the earthquake frequency reconstructed for the MF.

Citation: Hintersberger, E., Decker, K., Lomax, J., and Lüthgens, C.: Implications from palaeoseismological investigations at the Markgrafneusiedl Fault (Vienna Basin, Austria) for seismic hazard assessment, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2017-126, in review, 2017.
Esther Hintersberger et al.
Esther Hintersberger et al.
Esther Hintersberger et al.

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Short summary
The Vienna Basin is a low seismicity area, where historical data do not identify all potential earthquake sources. Despite observed Quaternary offset, there are no earthquakes along the Markgrafneusiedl Fault (MF). Results from 3 palaeoseismic trenches show evidence for 5–6 earthquakes with magnitudes up to M = 6.8 during the last 120 ka. Therefore, the MF should be considered as a seismic source, together with similar faults in the Vienna Basin, increasing the seismic potential close to Vienna.
The Vienna Basin is a low seismicity area, where historical data do not identify all potential...
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