Quaternary Science Reviews 24 (2005) 321–336 3-D mapping of segmented active faults in the southern Vienna Basin Ralph Hinsch à , Kurt Decker, Michael Wagreich Institute of Geology, University of Vienna, Althanstr. 14, A-1090 Vienna, Austria Received 6 December 2002; accepted 27 April 2004 Abstract In this paper we present novel data on the location and kinematics of seismically active fault segments of the Vienna Basin Transfer Fault System in the southern Vienna Basin. Spatial mapping of active faults and kinematical analyses are based on commercial 3-D reflection seismic data, geomorphological features such as tilted Quaternary river terraces and fault scarps, the geometry of subsided Quaternary basins, and published geodetic data. Accordingly, active faulting in the southern Vienna Basin occurs partly by reactivation of the Miocene fault system related to the formation of the Vienna pull-apart basin between c. 17 and 8 Ma. Two domains of Quaternary and active faults can be distinguished with, (1) predominantly strike-slip and (2) mainly normal faulting. (1) A seismically active NE-striking sinistral strike-slip fault zone with large negative flower structures is mapped at the south-eastern margin of the basin. Subsidence within the reflection seismically imaged flower structure is documented by up to 1000 m of throw since Pannonian times and the accumulation of up to 150 m thick Quaternary gravels. At the surface the fault zone is characterized by en-echelon faults with some prominent scarps. (2) Major E-dipping normal faults branch off from the transfer strike-slip fault system. The normal faults extend into the central and western part of the basin as well as into the urban area of Vienna. Close to Vienna, the normal offset along such a normal fault is at minimum 300 m since Pannonian times. Surface expressions of active normal faulting are tilted Quaternary terraces of the Danube river and tilted ancient land surfaces in the hanging wall of the normal faults. The mapped active normal faults are kinematically linked by a common detachment horizon, which is in contact with the seismically active strike-slip zone along the south-eastern border of the basin. Northeast of the Vienna Basin the seismically active zone continues as a straight line indicating a rather linear transfer fault zone than a pull-apart step over geometry. r 2004 Elsevier Ltd. All rights reserved. 1. Introduction The southern Vienna Basin is a prominent site of moderate seismicity with medium sized earthquakes (M 0 5.0–5.5) returning at periods of several decades (ZAMG, 2001; e.g., Schwadorf 1927 with M=5.2; Fig. 1). The distribution of earthquake epicentres, active fault kinematics resolved from focal solutions, and the few available dynamic data suggest that earthquakes occur on reactivated faults of the Vienna Basin Transfer Fault System, which are inherited from Miocene strike-slip faulting and pull-apart formation (Decker et al., 2005). Miocene deformation in the Vienna Basin was distributed over a dense network of kinematically linked faults covering the entire area of the basin and the adjacent basin margins. These faults are generally very well known due to extensive hydrocarbon exploration in the basin providing several thousand kilometres of 2-D seismic, c. 500 km 2 of 3-D seismic data, and several thousand drill holes (Sauer et al., 1992; Kro¨ll and Wessely, 1993). Major faults typically are spaced at distances of only few kilometres showing splays and branches, and converge to depth (Fig 1). The past kinematics of the faults and their interaction has been analysed by several studies (Fodor, 1995; Decker, 1996; see Decker et al., 2005, for a review). ARTICLE IN PRESS 0277-3791/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2004.04.011 à Corresponding author. Current address: Rohoel-Aufsuchungsge- sellschaft AG, Schwarzen bergerplatz 16, A-1015 Vienna, Austria Tel.: +43-1-50116-301; fax: +43-1-50116-223. E-mail address: ralph.hinsch@rohoel.at (R. Hinsch).