engleski

2D Seismic and Gravity Modelling in the area of Dinarides and SW part of the Pannonian Basin

Deep seismic exploration has been carried out on the profile ALP07 in the framework of the international scientific project ALP 2002-Seismic Exploration of the Alpine Lithosphere, whose scientific objective is to acquire fundamental data about deep structures in crust and upper mantle. The ALP07 profile is set up approximately perpendicular to extension of geological structures, respectively to the dinaridic direction and covers areas of the Dinarides and edge part of the Pannonian basin in Croatia. Two-dimensional interpretation has been carried out by automatic tomographic inversion and forward modelling based on the Ray Tracing method. Two-dimensional gravity modelling on the profile ALP07 has been performed in order to reducing of the interpretation ambiguity. However, new significance has been associated to some events on the seismic profile, so gravity modelling has been more useful than expected. Depths of the Mohorovicic discontinuity on the seismic model obtained by the forward modelling are the greatest in the area of the Dinarides (40 km). Depths in the area of the Pannonian Basin are in the range 20-30 km with the smallest value at the end of the profile. Depth changes are not smooth and uneven relief of the Mohorovicic discontinuity can be noticed. Seismic tomographic model indicates this event, as well. In the upper crust seismic velocities are generally very low, around 6 km/s, but with lateral variations. Two anomalies of higher velocities can be noticed: shallow anomaly in the beginning and deeper anomaly in the center of the profile. These anomalies can be also seen on the tomographic model. Relatively high seismic velocities characterize the lower crust in the area of the Dinarides (6.6-7.1 km/s), but in the area of the Pannonian Basin velocities are very low, around 6.0 km/s. According to the velocity distribution there is no need to divide the crust on the upper and the lower, but the crust can be considered as unique layer. This conclusion is also confirmed by the gravity modelling. Therefore two types of crust are defined: Pannonian Crust and Dinaridic Crust, which are separated by wide Transition Zone. This zone is characterized by sharp changes of seismic velocities and densities that point to tectonic anomalies and fracturing.

ALP2002 project; crustal structure; Dinarides; Pannonian basin

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