stress orientations and active fault kinematics of the vienna basin fault system, austria

AIM Annual Meeting, Bratislava, 29-30.09.2010

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


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

Outline


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


Decker et al. 2005, QSRHinsch et al. 2005, QSR

Hinsch & Decker 2004, Terra NovaSalcher et al. submitted, Basin Research

Data Background


Segment boundaries defined by fault bends and branchlines of major normal faults

„Rough“ strike-slip fault with marked changes of fault strike at depth

Strike-Slip Fault Kinematics

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


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


3D fault geomoetry


Quaternary fault map

Quaternary faults

ZAMG 2008

NE-striking seismic strike-slip fault at the SE margin of the

Miocene pull-apart basin

Section 1


system

Section 2

Section 3

Section 3


Decker et al., QSR 2005

230 prel.250 prel.242 ± 29

208 ± 23

232 ± 41261 ± 32 295 ± 32

259 ± 26278 ± 29284 ± 28292 ± 35

OSL ages (Feldspar)J. LOMAX

Normal Branch Faults


Markgrafneusiedl Fault cutting the

Gänserndorf Terrace (250 ky) and overlying

loess (20 - 15 ky)


Spatial fault data from Quaternary fault maps (surface) and 2D/3D seismic

Hölzel et al., Marine Petrol Geol. 2010Hölzel et al., AJES 2008

- 1 0 0 0

1 0 1 01 2 k m1 2 k m2 0 2 03 0 3 04 0 4 0

6 0 6 05 0 5 0

S t r e n g t h ( M p a )

V i e n n a B a s i nS t y r i a n B a s i nT a u e r n W i n d o w

G e n s e r e t a l . 1 9 9 6 S a c h s e n h o f e r1 9 9 6 L a n k r e i j e r( 1 9 9 8 )

Depth (km)

00 01 0 0 01 0 0 0 1 0 0 0

d r yw e t

L i t h o s p h e r i c s t r e n g t h m o d e l l i n g

2 00 4 0 6 0N o . o f e v e n t s

F o c a l d e p t h s o f e a r t h q u a k e s

- 1 0 0 0

1 0 1 01 2 k m1 2 k m2 0 2 03 0 3 04 0 4 0

6 0 6 05 0 5 0

S t r e n g t h ( M p a )

V i e n n a B a s i nS t y r i a n B a s i nT a u e r n W i n d o w

G e n s e r e t a l . 1 9 9 6 S a c h s e n h o f e r1 9 9 6 L a n k r e i j e r( 1 9 9 8 )

Depth (km)

00 01 0 0 01 0 0 0 1 0 0 0

d r yw e t

L i t h o s p h e r i c s t r e n g t h m o d e l l i n g

2 00 4 0 6 0N o . o f e v e n t s

F o c a l d e p t h s o f e a r t h q u a k e s

Faults root in the Alpine-Carpathian floor thrust Hypocenter depths < 12 km (90 % of events)

3D fault geomoetry


Quaternary faults

ZAMG 2008

NE-striking seismic strike-slip fault at the SE margin of the

Miocene pull-apart basin


system

Seísmicity and active fault kinematics


Mostly N to NNW-trending P-axes

Strike-slip >> Normal faulting

Few but reliable contradicting data (blue beachballs)

FPS and fault kinematics


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)


Borehole breakout on opposing sides of the borehole wall (180°)

Induced tensile fractures 90° to borehole breakout, inclined and often with stair stepping appearance

Induced centerline fractures 90° to borehole breakout, vertical

Stress data (SH orientations)

FMI examples: breakouts and induced tensile fractures

FMI Acoustic Acoustic traveltime


FMI Acoustic FMI Acoustic

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°)


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


Stress data (SHmax orientations)

Significant stress change of ~ 40° at faults such as Steinberg Fault

Marsch et al., 1990: Decker et al., 2005


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


Stress partitioning occurs at active faults delimiting the wrench zone to the NW

Thanks to OMV Austria (C. Astl, G. Arzmüller, H. Peresson)

Conclusions

stress orientations and active fault kinematics of the vienna basin fault system, austria

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