Active tectonic deformation and associated earthquakes: a case study—South West Carpathians Bend zone

Abstract

Active tectonic deformation is continuously shaping the landscape in the Alpine Orogenic system. Earthquakes are clear proves of neotectonic deformation process. In the Romanian Carpathians the most active deformation is recorded in the South Eastern Carpathian Bend Zone. Nevertheless, seismicity associated to latest orogenic stage of active deformation is not limited to this area. Other seismic regions, like the South West Carpathians Bend Zone, were identified. Recently, several earthquake sequences were recorded in the Caransebes-Mehadia (CMB) and Hateg basins (HB). These sedimentary basins developed over the South Carpathians, Getic/Supra Getic and Danubian basement napes, their evolution being related with the N-ward tectonic transport of the Carpathian Orogen, in the current position, during the Paleogene-Quaternary times. The aim of the present study is to perform a thorough analysis of the earthquakes recorded in these two basins in correlation with the observed geological structure to better understand and constrain the neotectonic processes affecting the SW Carpathians Bend Zone. The focal mechanisms determined for HB show a predominant strike-slip faulting component with the principal axes oriented approximately NW–SE (compression) and NE–SW (extension), a reorientation from the N-S one described for the Pliocene–Pleistocene phase. The focal mechanisms in CMB imply N–S extension with normal or strike-slip faulting. We argue that the present day tectonic processes are not restricted to the SE Carpathians Bend zone, as previously inferred. Instead they affect a much larger area of the Carpathian Orogen, like the SW Carpathians Bend zone.