Investigation of the relationship between subsurface structures and mass movements of the high loess bank along the River Danube in Hungary

Relationships between regional tectonics, subsurface structures and mass movements are investigated on the high loess bank of the River Danube at Dunaföldvár based on remote sensing data, gravity and tilt measurements. The geology and morpho-tectonics of the area were derived from remote sensing images. The basement structure under the high loess bank and in its surroundings was revealed by gravimetric measurements. On the basis of these data a model for the surface mass movements was developed and compared to the results of the surface tilt measurements. Two explanations for the measured tilt have been considered, a tectonic one and a geomorphologic one. The data in the former are treated as being the consequence of recent tectonic movements. According to this approach the SSW tilt on the top of the high bank originates from the very slow movements of Felső-Öreg-hegy towards the southwest as a result of an ENE-WSW compression. In the geomorphologic explanation the movements are the consequence of erosion and undercutting of the riverbank caused by the Danube, which has led to the slow loss of the base support of the high bank, resulting in slow sliding eastwards accompanied by counterclockwise rotation of the Felső-Öreg-hegy block. In accordance with these explanations, most probably the measured tilt rate is the consequence of both tectonic and geomorphologic processes. In order to prove active tectonism on the territory long-term tilt and geodetic deformation measurements are necessary on a wider area than the recent test site.