Doctor's Theses (authored and supervised):

U. Mitterbauer:
"3D Geschwindigkeitsstruktur des ostalpinen Slabs - Ergebnis einer tomographischen Studie";
Supervisor, Reviewer: E. Brückl, W. Lenhardt; Department für Geodäsie und Geoinformation E120.3, 2017; oral examination: 2017-06-29.

English abstract:
During the last two decades teleseismic studies have been undertaken to reveal the structure
of the upper mantle below the Alpine-Mediterranean area. A deep slab, which is interpreted as
subducted oceanic lithosphere, can be seen as a broad anomaly above the 670 km
discontinuity. More shallow slabs can be found beneath the Alpine arc and are interpreted as
continental lower lithosphere. Based on these images, advances in our understanding of active
and passive tectonic processes have been achieved.
Nevertheless, there are still open questions and debates are on-going. The geometry of the
subducted lithosphere at the transition to the Pannonian Basin and a change of polarity
observed in the shallow slabs are still disputed topics. The passive teleseismic experiment
ALPASS was designed to shed light on such problems. Between 2005 and 2006 teleseismic
waveforms from 81 earthquakes were recorded at 75 temporary and 79 permanent stations.
Based on this data, a teleseismic model was created between 60 and 500 km depth. A steeply
to vertically dipping "shallow slab" below the Eastern Alps was clearly resolved down to a
depth of 250 km. It is interpreted as European lower lithosphere detached from the crust and
subducted during post-collision convergence between Adria and Europe. Below the
Pannonian realm, low velocities prevail down to ~ 300 km depth. They are consistent with the
concept of a Pannonian lithospheric fragment that underwent strike-slip deformation relative
to the European plate and extension during the post-collision phase of the Alpine orogeny. At
depths between 350 and 400 km, a "deep slab" extends from below the central Eastern Alps to
under the Pannonianrealm. This is interpreted as subducted lithosphere of the Alpine Tethys.
At greater depth, there is a continuous transition to the high velocity anomaly above the 670
km discontinuity.
An average was built from the collected data set and from published works dealing with
tomographic studies that overlap in the area of study, and this was used as a basis for
compilation of synthetic models. Using the same raytracing-algorithm and traveltimes for the
actual registered events and stations, the models constructed in this manner were then
inverted. This made it possible to test the structures calculated during the tomography. Close
examinations were conducted to see if there is a possible connection within the shallow slab
and betweeen the shallow and the deep slab. It could be shown that the shallow slab is
connected, but it was not possible to make a statement concerning the connection between the
deep and the shallow slab.
Lastly, a temperature model was compiled from the vP - model. For this assessment, several
constraints concerning relations between the three dimensional distribution of seismic
velocities and physical parameters like temperature and density were applied. By these means,
the plausibility of the model and the tectonic origin of the slab was verified.

Electronic version of the publication:

Related Projects:
Project Head Ewald Brückl:
ALPASS - Seismisches Monitoring der Lithosphäre und des oberen Mantels in den Alpen 2. bis incl. 4. Projektjahr

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