Description:
<jats:p>Abstract. In the frame of the AlpArray project we analyse
teleseismic data from permanent and temporary stations of the Alpine region
to study seismic discontinuities down to about 140 km depth. We average
broadband teleseismic S-waveform data to retrieve S-to-P converted signals
from below the seismic stations. In order to avoid processing artefacts, no
deconvolution or filtering is applied, and S arrival times are used as
reference for stacking. We show a number of north–south and east-west
profiles through the Alpine area. The Moho signals are always seen very
clearly, and negative velocity gradients below the Moho depth are also
visible in a number of profiles. A Moho depression is visible along larger
parts of the Alpine chain. It reaches its largest depth of 60 km beneath the
Tauern Window. However, the Moho depression ends abruptly near about
13∘ E below the eastern Tauern Window. This Moho depression may
represent the crustal trench, where the Eurasian lithosphere is subducted
below the Adriatic lithosphere. East of 13∘ E an important
along-strike change occurs; the image of the Moho changes completely. No
Moho deepening is found in this easterly region; instead the Moho bends
up along the contact between the European and the Adriatic lithosphere all
the way to the Pannonian Basin. An important along-strike change was also
detected in the upper mantle structure at about 14∘ E. There, the
lateral disappearance of a zone of negative velocity gradient in the
uppermost mantle indicates that the S-dipping European slab laterally
terminates east of the Tauern Window in the axial zone of the Alps. The area
east of about 13∘ E is known to have been affected by severe
late-stage modifications of the structure of crust and uppermost mantle
during the Miocene when the ALCAPA (Alpine, Carpathian, Pannonian) block was
subject to E-directed lateral extrusion.
</jats:p>