The Pannonian Basin, situated in Central Europe, is surrounded by the Alpine, Carpathian
and Dinaric orogens. To understand its tectonic characteristics and evolution, we
determine a shear wave velocity model of its crust, mantle lithosphere and asthenosphere
consistently by jointly inverting Rayleigh wave phase velocities measured consistently
from earthquake (EQ) and ambient noise (AN) data. For the AN data, continuous waveform
data were collected from 1254 stations, covering an area within 9° from the centre
of the Pannonian Basin during the time period from 2006 to 2018. This data set enabled
the extraction of over 164 464 interstation Rayleigh phase-velocity curves, after
applying a strict quality control workflow. For the EQ data set more than 2000 seismic
events and about 1350 seismic stations were used in the broader Central and Eastern
European region between the time-span of 1990 to 2015, allowing us to extract 139
987 quality controlled Rayleigh wave phase-velocity curve. Using the combined data
set, a small period- and distance-dependent bias between ambient noise and earthquake
measurements, mostly below 1 per cent but becoming larger towards longer periods has
been found. After applying a period and distance dependent correction, we generated
phase-velocity maps, spanning periods from 5 to 250 s. 33 981 local dispersion curves
were extracted and a new approach is introduced to link their period-dependent roughness
to the standard deviation. Using a non-linear stochastic particle swarm optimization,
a consistent 3-D shear wave velocity model (PanREA2023) encompassing the crust and
upper mantle down to 300 km depth was obtained with a lateral resolution reaching
about 50 km at the centre of the study area for shorter periods. The crust beneath
the Carpathian orogen exhibits a distinct low-velocity anomaly extending down to the
Moho. It is referred to as Peri-Carpathian anomaly. Similar anomalies were observed
in the Northern Apennines, while the Eastern Alps and Dinarides, as collisional orogens,
generally demonstrate higher velocities in the upper crust. High crustal shear wave
velocities are also evident in the Bohemian Massif and the East European Craton. The
brittle upper crust of the Pannonian Basin is characterized by alternating NE–SW trending
high- and low-velocity anomalies: the western and central Pannonian low-velocity anomalies
and the Transdanubian and Apuseni high-velocity anomalies related to Miocene sedimentary
basins and intervening intervening interbasinal highs exposing Pre-Cenozoic rocks
including crystalline basement rocks. Beneath the Southeastern Carpathians, a NE-dipping
slab was identified, extending to depths of at least 200 km, while a slab gap is evident
beneath the Western Carpathians. A short south-dipping Eurasian slab was imaged beneath
the Eastern Alps down to only 150–200 km depth. The Adriatic lithosphere is subducting
near-vertically dipping beneath the Northern Apennines, and a slab gap was observed
beneath the Central Apennines. In the Northern Dinarides, a short slab was evident,
reaching depths of around 150 km. The Southern Dinarides featured a thinned but possibly
incompletely detached slab.
