Transcript Stress orientations and active fault kinematics of the Vienna Basin
Stress orientations and active fault kinematics of the Vienna Basin Fault System, Austria K. Decker
(1)
, G. Burmester
(2)
& W. Lenhardt
(3)
(1) University Vienna (2) Fronterra Geosciences, Vienna, Austria (3) ZAMG Vienna AIM Annual Meeting, Bratislava, 29-30.09.2010
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 (S H ) from high-quality FMI and caliper analyses S H orientation and evidence for stress partitioning at active faults
Conclusions
AIM Annual Meeting, Bratislava, 29-30.09.2010
AIM Annual Meeting, Bratislava, 29-30.09.2010
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
Data Background
Decker et al. 2005, QSR Hinsch et al. 2005, QSR Hinsch & Decker 2004, Terra Nova Salcher et al. submitted, Basin Research AIM Annual Meeting, Bratislava, 29-30.09.2010
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 AIM Annual Meeting, Bratislava, 29-30.09.2010
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
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 AIM Annual Meeting, Bratislava, 29-30.09.2010
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
3D fault geomoetry
AIM Annual Meeting, Bratislava, 29-30.09.2010
ZAMG 2008
AIM Annual Meeting, Bratislava, 29-30.09.2010
Quaternary faults Section 3
Quaternary fault map
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
Normal Branch Faults
OSL ages (Feldspar) J. LOMAX
208 ± 23 230 prel.
250 prel.
242 ± 29 232 ± 41 261 ± 32 295 ± 32 259 ± 26 278 ± 29 284 ± 28 292 ± 35
AIM Annual Meeting, Bratislava, 29-30.09.2010
Decker et al., QSR 2005
AIM Annual Meeting, Bratislava, 29-30.09.2010
Markgrafneusiedl Fault cutting the Gänserndorf Terrace (250 ky) and overlying loess (20 - 15 ky)
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 AIM Annual Meeting, Bratislava, 29-30.09.2010
Seísmicity and active fault kinematics
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
ZAMG 2008
AIM Annual Meeting, Bratislava, 29-30.09.2010
Quaternary faults
AIM Annual Meeting, Bratislava, 29-30.09.2010
FPS and fault kinematics
Mostly N to NNW-trending P-axes Strike-slip >> Normal faulting Few but reliable contradicting data (blue beachballs)
AIM Annual Meeting, Bratislava, 29-30.09.2010
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)
Stress data (S H 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 °) FMI AIM Annual Meeting, Bratislava, 29-30.09.2010
Acoustic Acoustic traveltime Induced centerline fractures 90 ° to borehole breakout, vertical
FMI Acoustic AIM Annual Meeting, Bratislava, 29-30.09.2010
FMI Acoustic
Stress data (S H ) 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 °)
AIM Annual Meeting, Bratislava, 29-30.09.2010
Stress data (S H orientations)
Most data indicate N to NNW oriented S H Significant stress changes occur at normal faults slplaying from the sinistral wrench fault
Stress data (S Hmax orientations)
Significant stress change of ~ 40 ° at faults such as Steinberg Fault Marsch et al., 1990: Decker et al., 2005 AIM Annual Meeting, Bratislava, 29-30.09.2010
AIM Annual Meeting, Bratislava, 29-30.09.2010
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
AIM Annual Meeting, Bratislava, 29-30.09.2010
Conclusions
Stress partitioning occurs at active faults delimiting the wrench zone to the NW Thanks to OMV Austria (C. Astl, G. Arzmüller, H. Peresson)