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Stress orientations and active fault kinematics of the Vienna Basin Fault System, Austria

Stress orientations and active fault kinematics of the Vienna Basin Fault System, Austria. K. Decker (1) , G. Burmester (2) & W. Lenhardt (3). University Vienna (2) Fronterra Geosciences, Vienna, Austria (3) ZAMG Vienna. Outline. Introduction Local setting and fault kinematics

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Stress orientations and active fault kinematics of the Vienna Basin Fault System, Austria

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  1. Stress orientations and active fault kinematics of the Vienna Basin Fault System, Austria K. Decker (1), G. Burmester(2) & W. Lenhardt (3) • University Vienna • (2) Fronterra Geosciences, Vienna, Austria • (3) ZAMG Vienna

  2. Outline • Introduction • Local setting and fault kinematics • Active tectonics • 2D and 3D geometry of active faults of the Vienna Basin Fault System • Seismicity, FPS and aktive fault kinematics • Stress orientations • Stress data (SH) from high-quality FMI and caliper analyses • SH orientation and evidence for stress partitioning at active faults • Conclusions

  3. Active faults in the Vienna Basin NE-striking strike-slip fault at the SE margin of the Miocene pull-apart Moderate seismicity N-striking normal splay faults branching off the strike-slip system No historical seismicity

  4. Data Background Decker et al. 2005, QSR Hinsch et al. 2005, QSR Hinsch & Decker 2004, Terra Nova Salcher et al. submitted, Basin Research

  5. Strike-Slip Fault Kinematics • Segment boundaries defined by fault bends and branchlines of major normal faults • „Rough“ strike-slip fault with marked changes of fault strike at depth • Most of the extension at releasing bends is transferred to normal faults • Normal faults are linked to the strike-slip system via a common detachment

  6. Normal Branch Faults • Segment boundaries defined by fault bends and branchlines of major normal faults • „Rough“ strike-slip fault with marked changes of fault strike at depth • Most of the extension at releasing bends is transferred to normal faults • Normal faults are linked to the strike-slip system via a common detachment

  7. 3D fault geomoetry

  8. Quaternary fault map Section 3 ZAMG 2008 NE-striking seismic strike-slip fault at the SE margin of the Miocene pull-apart basin Section 1 N-striking normal splay faults branching off the strike-slip system Section 2 Section 3 Quaternary faults

  9. Normal Branch Faults 208 ± 23 OSL ages (Feldspar) J. LOMAX 230 prel. 250 prel. 242 ± 29 232 ± 41 261 ± 32 295 ± 32 259 ± 26 278 ± 29 284 ± 28 292 ± 35 Decker et al., QSR 2005

  10. Markgrafneusiedl Fault cutting the Gänserndorf Terrace (250 ky) and overlying loess (20 - 15 ky)

  11. 3D fault geomoetry • Faults root in the Alpine-Carpathian floor thrust • Hypocenter depths < 12 km (90 % of events) Spatial fault data from Quaternary fault maps (surface) and 2D/3D seismic Hölzel et al., Marine Petrol Geol. 2010 Hölzel et al., AJES 2008

  12. Seísmicity and active fault kinematics ZAMG 2008 NE-striking seismic strike-slip fault at the SE margin of the Miocene pull-apart basin N-striking normal splay faults branching off the strike-slip system Quaternary faults

  13. FPS and fault kinematics Mostly N to NNW-trending P-axes Strike-slip >> Normal faulting Few but reliable contradicting data (blue beachballs)

  14. FPS and fault kinematics Preferred nodal plane highlights N to NE-striking sinistral faults In line with makroseimick data (orientation of inner isoseismals) Few contradicting data (blue beachballs)

  15. Stress data (SH orientations) FMI examples: breakouts and induced tensile fractures Induced tensile fractures 90° to borehole breakout, inclined and often with stair stepping appearance Borehole breakout on opposing sides of the borehole wall (180°) Induced centerline fractures 90° to borehole breakout, vertical FMI Acoustic Acoustic traveltime

  16. Stress data (SH) FMI examples Induced tensile fractures 90° to borehole breakout, inclined and often with stair stepping appearance Borehole breakout on opposing sides of the borehole wall (180°) FMI Acoustic FMI Acoustic

  17. Stress data (SH orientations) Most data indicate N to NNW-oriented SH Significant stress changes occur at normal faults slplaying from the sinistral wrench fault

  18. Stress data (SHmax orientations) Significant stress change of ~ 40° at faults such as Steinberg Fault Marsch et al., 1990: Decker et al., 2005

  19. Conclusions Both FPS and stress data are consistent with geological / geodetic evidence for sinistral strike-slip faulting Stress partitioning occurs at active faults delimiting the wrench zone to the NW

  20. Conclusions Stress partitioning occurs at active faults delimiting the wrench zone to the NW Thanks to OMV Austria (C. Astl, G. Arzmüller, H. Peresson)

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