Active Seismotectonic Deformation in Front of the Dolomites Indenter, Eastern Alps

Abstract

We use earthquake focal mechanisms to study present‐day deformation and stress in the western part of the Eastern European Alps. We define the following regions, based on seismicity and kinematically compatible focal mechanism types: (1) the northern and western parts of the Dolomites indenter, the western and central Tauern Window, and the northern Alpine margin and foreland lack significant seismicity. (2) The indenter boundaries are characterized by strike‐slip faulting. Based on earthquake and geodetic data, the western and northern indenter boundaries are active sinistral and dextral strike‐slip/oblique slip faults. (3) West and north of the indenter corner, we observe normal and strike‐slip faulting in an up to 70 km‐wide zone. From west to east, the minimum horizontal stress rotates clockwise about 10–20°, from NE to ENE. (4) North of (3), east of the Swiss/Austrian border, we find evidence for N to NNW directed thrust faulting, and local orogen‐parallel extension. From our results and geodetic data, we infer that relative to a fixed northern foreland, NNW directed indentation is transferred at depth via the Sub‐Tauern thrust system to this 100‐km‐wide zone of localized thrusting. A lack of evidence for major, active strike‐slip faulting north of the Tauern Window is in line with geodetic data, which show no significant velocity difference between the northern part of the Eastern Alps and their foreland.

Differential uplift on the boundary between the Eastern and the Southern European Alps: Thermochronologic constraints from the Brenner Base Tunnel

“…The Austroalpine nappe stack overlies the Penninic and Sub‐Penninic units (Reiter et al, , the tunnel cross section presented coincides with the trace of their figure 8). Austroalpine units can be subdivided into a northern part affected by Eoalpine metamorphism (lower nappes during orogeny) which was juxtaposed to a weakly to non‐affected (uppermost nappes) southern one (Borsi, Moro, & Ferrara, ) by a set of faults (Figure , blue) that mark the ‘Southern limit of Alpine metamorphism’ (SAM, Hoinkes et al, ).…”

Deriving a New Crustal Model of Northern Adria: The Northern Adria Crust (NAC) Model

“…The most seismically active region is the external front of the Southern Alps, and of the Dinarides. The seismic activity is concentrated at shallow depth (Viganò et al, 2015;Bressan et al, 2018a,b;Reiter et al, 2018). Also the Friuli, 1976 earthquake, the greatest event recorded in the instrumental period in this area, has a hypocentral depth of about 5-10 km (Slejko, 2018).…”

Structural evidence of in-sequence and out-of-sequence thrusting in the Karwendel mountains and the tectonic subdivision of the western Northern Calcareous Alps

“…In this context, the Karwendel zone of slices appears to be a zone of out-of-sequence duplexing uplifting the southern part of the Karwendel thrust sheet. See Reiter et al (2018) for a more elaborated cross section nearby. sedimentary succession of the Tirolic thrust sheets, two sedimentary units are characteristic: the Upper Jurassic Oberalm Fm.…”