Tectonic activity in the Croatian part of the Pannonian basin

Abstract

Three main stages in structural development of the SW Pannonian basin are differentiated: the onset of extensional tectonics between the Oligocene and the Early Miocene, main extensional processes in the Early and Middle Miocene and prevailing transpression in the Pliocene and Quaternary. The neotectonic phase is given special attention in this paper. Structural fabrics allow to subdivide the area into three large structural zones: corresponding to the Western, Southern and Central marginal part of the Pannonian basin in Croatia. These zones are bounded by important faults: the Periadriatic–Drava fault, the Medvednica fault zone and the southern marginal fault of the Pannonian basin. The recent displacements within the Dinarides and the Eastern Alps form the boundary conditions for active transpressional deformation in the Western marginal part of the Pannonian basin. Dextral transcurrent displacement is evident in the zone of the Periadriatic–Drava wrench fault. The formation of the new types of structures is observed, especially in zones of compression along the faults. Narrowing of the area between the Sava and Drava rivers causes structural changes in the marginal parts of the corresponding basins, i.e. in the areas close to the Slavonian Mts. Recent tectonic activity is marked by the occurrence of earthquakes which are most common in the northwestern part of Croatia. The spatial distribution of hypocentres and of seismotectonically active zones is used to reconstruct probable displacements and the structural style of deformation in depth. The earthquake sources in the vicinity of the Medvednica fault and the Periadriatic–Drava fault are given special attention.