Strike-slip tectonics in the Pannonian basin based on seismic surveys at Lake Balaton

Strike-slip tectonics has been the dominant style of deformation during the neotectonic (Pliocene and Quaternary) evolution of the Pannonian basin. Main faults are exposed in the ""island mountains"" of the basin, but strike-slip tectonic features can be best studied in the basin fill by seismic data. Lake Balaton offers the opportunity to carry out high to ultra-high-resolution seismo-acoustic surveys to image stratigraphic and tectonic features in the central part of the Pannonian basin. Several campaigns in the lake using different acquisition techniques have resulted in more than 2000-km seismo-acoustic profiles with a range of resolutions and penetration depths. Interpretation of faults and folds shows a few kilometers wide shear zone below the lake in Late Miocene-Pliocene strata. This zone can be identified as the continuation of the Balatonfo line known onshore to the east of the lake. Mapping revealed a set of duplex structures and highlighted the importance of this shear zone in the formation of Lake Balaton. Comparison of our results to analogue clay models suggests that the observed shear zone is sinistral and the horizontal displacement is on the order of hundreds of meters. Looking at 3D industrial seismic data to the south of the lake, we suggest that the first-order Balaton line, which represents the continuation of Periadriatic line, is also sinistral and characterized by small horizontal displacement of about 1.0-1.5 km during Pliocene and Quaternary times. This indicates a 0.2-0.3 mm/year average slip rate, which is compatible with recent GPS measurements.