LATE QUATERNARY TRANSPRESSIONS SOUTH OF LAKE BALATON, HUNGARY

The Somogy Hills is a hilly area, located immediately south of Lake Balaton, Hungary. The region has two well defined valley systems. 1.: few tens of kilometres long and nearly paralell „transversal” valleys with N-S to NNW-SSE direction. 2.: „longitudinal” valleys of NE-SW – E-W strike. We analysed Quaternary and directly underlying Upper Miocene (Pannonian) outcrops by structural, tectono-morphological and sedimentological methods to quantify the main fault directions; to separate mass movements from faulting and folding; and to separate earthquake-induced sediment deformations from other (e.g. periglacial) effects. Quaternary outcrops showed several consistent directions of faulting, and co-depositional seismic activity (seismites). Three different Mohr-sets of faults could be differentiated in Quaternary sediments. In Pannonian outcrops four different sets were separated, three of which are common to the Quaternary ones. The three sets are considered Late Quaternary since all cut young loess sections and have sharp morphological expressions. In the transversal valleys NNE-SSW striking en echelon folds, normal and Riedel faults can be deteced. Both affect the present day surface. Riedel faults can be seen as renewed small valley- opening from the last decades until today. On the basis of the fault and fold patterns this movement refers to a marked left lateral transpression along the transversal valleys. NE-SW – E-W longitudinal valleys show right lateral strike slip motion at the same time. This research was supported by the Hungarian National Research Fund (OTKA T-037593).