Neogene to recent faults in Eastern Alps

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Alpenseminar by Mjahid Zebari.

After the Exkursionswoche break, we had a presentation about Neogene to recent faults in Eastern Alps by Mr. Zebari on 15th of June. He won't join the excursion this year, but he gave a comprehensive views with various methods on new tectonics.

The content of the talk include the following.


Tectonic map of the Eastern Alps [modified after Handy et al., 2010].(Bertrand et al, 2017)

Main Faults System
- N-S Normal Fault:  Brenner fault,  Katschberg fault
- Strike-slip faults:
  Sinistral(to the NORTH):
Inntal fault, Salzachtal‐ Ennstal‐ Mariazell‐ Puchberg fault, Mur‐Mürzf ault, Defereggen‐ Antholz‐ Vals fault.
  Dextral(to the SOUTH):
Periadriatic fault, Pöls‐Lavanttal fault, Hochstuhlfault, Mölltal fault.

Present-day deformation of the eastern Eastern Alps(J. Reinecker 7 W. A. Lenhardt, 1999)

Present Day Stress
Fault plane solutions exhibit mainly sinistral strike-slip movements along this zone.
Distinct seismically active zone is the NNW/SSE-trending northern part of the Lavanttal fault with clear dextral strike-slip kinematics.

The Friuli region experiences high seismicity with magnitudes up to 6.5. Kinematics are strike-slip faulting in the eastern part and thrust faulting in the western and central parts.



Present day slip rates


Schematic tectonic and kinematic map showing the major findings. (Serpelloni et al.,  2016) 
The northern Adriatic region is moving consistently with the Adriatic microplate .
The northern Dinaric area presents small residual motions with respect to Adria.

Deformation Time
Deformation Time started at least in Middle Oligocene, continued to be  active throughout
Neogene. (Wölflrt et al, 2011)Two peaks of deformation are Oligocene (32-30 Ma) and E-M Miocene (21-15 Ma).
In PAF, change from sinistralto dextralat ∼30 Ma.

Displacement trajectories and polarities of Oligocene to r ecent subduction zones within theAlpine‐Carpathian‐Mediterranean realm [after Doglioni et al., 1991, 1997] in relation to extrusion of the Eastern Alps. (Wölflrt et al, 2011)

Regional Evolution

(a) From 30 to 15 Ma the Eastern Alps (EA) experienced oblique shortening due to stresses released by the quickly retreating Apennine subduction zone. OP, Oligocene plutons; SEMP, Salzachtal‐Ennstal‐Mariazell‐Puchberg fault system; P‐L FS, Pöls‐Lavanttal fault system.

(b) From 15 Ma to recent rotation and retreat of the Apennine slab released N‐S compressive stresses perpendicular to the strike of the orogen.

The Eastern Alps extended beyond the Dinaric subduction zone and became highly extensive. MV, Miocene volcanic; TW, Tauern Window; EA, Eastern Alps; MoF, Mölltal fault.


Shortening and Extension 
Balancing lateral orogenic float of the Eastern Alps: Retrodeformation of the Alpine wedges was carried out by restoration of their original position by the displacement data of the wedge-bounding faults. Displacement vectors show on map scale the amount of displacements and their north– south and east– west components. (Linzeret et al., 2002)

Tectonic model in Eastern Alps is mainly explained as lateral extrusion (Selverstone, 2005). 
Tectonic escapein a regime of overall compression (i.e., plane strain horizontal shortening of tectonic wedges driven by forces applied to their boundaries.
Extensional collapse in a regime of overall extension (i.e., gravitational spreading away from a potential energy high.
They are also shown by analogue model(Rosenberg, 2004) andnumerical model (Robl, 2008).


Lateral Extrusion in Eastern Alps during Neogene
N-S Oblique Convergence between two Strong Indenter Adria and Europe.(Reinecker,J., Lenhardt, W.,1999)
- Crustal thickness gradient, previously thickened, gravitationally unstable, thermally weakened.
- Back-arc extension in the Pannonian Basin due to subduction retreat and slab rollback in Carpathian.
- Flow freely eastward or pull (rollback)
- Presence of normal faults (detachments) in addition to strike-slip faults.


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