3-D mapping of segmented active faults in the Vienna Basin from integrated geophysical, geomorphological and geological data: building up an active fault database
Abstract
The Vienna Basin basin formed as a Miocene pull-apart basin along a sinistral transform system between the Eastern Alps and the Carpathians. Moderate seismicity in the southern Vienna Basin as well as thick Quaternary deposits in the center of the basin prove that part of the faults within the Miocene basin are active today. However, nearly no systematical data exist on the positions, segmentation, and geometry of active faults, which yield important input parameters for seismic hazard evaluations. Spatial mapping of active faults and kinematical analyses are based on 3-D reflection seismic data by OMV Austria, geomorphological features such as tilted Quaternary river terraces and fault scarps, the geometry of Quaternary basins, and published geodetic data. Interpretation of combined data sets are summarized in a map and an active fault catalog of for future seismic hazard evaluations. The map reveals two regions with different types of Quaternary and active faults. (A) The southern part of the Vienna Basin reveals a seismically active NE-striking sinistral strike-slip fault with a large negative flower structure. Recent activity of the flower structure is documented by the accumulation of up to 150 m thick Quaternary gravels. The Quaternary basin is limited by faults, depicted by 3-D seismics and near surface geophysics (Gegenleitner et al, 2003, this volume). At the surface, a prominent morphological scarp parallels the fault traces mapped from the 3-D seismic. (B) The western and central part of the Vienna Basin is characterized by major listric E-dipping normal faults branching off from the strike-slip fault system, which is localized in the seismically active area at the eastern border of the Basin. Deformation is partitioned on several normal faults via a common detachment horizon. These faults kinematically link up with the strike-slip fault system. At the surface normal faulting is documented by tilted Quaternary terraces of the Danube caused by the hangingwall collapse above listric faults. Major branch points are marked by changes in the geomorphological expression and Quaternary basin architecture, indicating a segmentation of the main fault along strike. We propose that at least one major mapped branch point coincide with a seismogenic segment-boundary at depth. This interpretation is supported by hypocenters clustering near the two adjacent fault segments mapped in the 3-D seismic survey. However, not all major branch points are presently defined well enough to allow an assessment of fault segment surfaces for the calculation of earthquake magnitudes.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....10272H