During the CELEBRATION 2000 seismic experiment, the Western Carpathians and Pannonian
basin region was investigated by a dense system of deep seismic sounding profiles.
In this paper, we present the results of modeling refracted and reflected waves employing
2D ray tracing for seven interlocking profiles that were jointly modeled and interpreted
with the constraint that the models match at the crossing points of the profiles.
The resulting P-wave velocity models reveal complex structures in the crust and large
variations in the depth of the Moho discontinuity (similar to 25-45 km). In the southern
part of the area, the relatively thin Pannonian basin crust consists of 3-7 km thick
sediments and two crustal layers with velocities of 5.9-6.3 km/s in the upper crust
and 6.3-6.6 km/s in the lower crust. In the central region, the upper crust of the
ALCAPA (Alpine-Carpathian-Pannonian) microplate contains a high velocity body of V-p
>= 6.4 km/s, which spatially corresponds with the Bukk Composite Terrane. The total
thickness of the ALCAPA crust is 1-2 km greater than in the adjacent Tisza-Dacia microplate.
To the north in the area of the Trans-European suture zone (TESZ) and Carpathian foredeep,
we observe a 10-20 km thick upper crust with low velocity (V-p <= 6.0 km/s). Sub-Moho
velocities have average values of 7.8-8.0 km/s for the Pannonian basin, while in the
Western Carpathians, the TESZ and the East European Craton (EEC) area, they are slightly
higher (8.0-8.1 km/s). Lower velocities beneath the ALCAPA and Tisza-Dacia microplates
could be caused by compositional variations and the significantly higher surface heat
flow. Beneath some profiles, reflectors in the lithospheric mantle were found sub-parallel
to the Moho but 10-20 km below it. Our integrated geophysical and geological analysis
indicates that the observed structure was created by collision of two lithospheric
plates with only a moderate degree of convergence. The northern plate consists of
older European tectonic units of the EEC and TESZ. However, the southern one consists
of younger tectonic units of the Western Carpathians and the back-arc Pannonian basin
that generated the ALCAPA and Tisza-Dacia microplates. We interpret the complex present
day structure to be the result of the soft continental collision between the ALCAPA
and Tisza-Dacia microplates and the south margin of the European plate, which was
mainly followed by the extensional process beneath the back-arc Pannonian basin. (C)
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