Tectonic activity in the Croatian part of the Pannonian basin

Three main stages in structural development of the SW Pannonian basin are d ifferentiated: the onset of extensional tectonics between the Oligocene and the Early Miocene, main extensional processes in the Early and Middle Mioc ene and prevailing transpression in the Pliocene and Quaternary. The neotec tonic phase is given special attention in this paper. Structural fabrics al low to subdivide the area into three large structural zones: corresponding to the Western, Southern and Central marginal part of the Pannonian basin i n Croatia. These zones are bounded by important faults: the Periadriatic-Dr ava fault, the Medvednica fault zone and the southern marginal fault of the Pannonian basin. The recent displacements within the Dinarides and the Eas tern Alps form the boundary conditions for active transpressional deformati on in the Western marginal part of the Pannonian basin. Dextral transcurren t displacement is evident in the zone of the Periadriatic-Drava wrench faul t. The formation of the new types of structures is observed, especially in zones of compression along the faults. Narrowing of the area between the Sa va 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 hy pocentres and of seismotectonically active zones is used to reconstruct pro bable displacements and the structural style of deformation in depth. The e arthquake sources in the vicinity of the Medvednica fault and the Periadria tic-Drava fault are given special attention. (C) 1998 Elsevier Science B.V. All rights reserved.