Werner Chwatal

Detecting fold structures at the southern flank of the Neogene Vienna Basin in eastern Austria using near-subsurface geophysical methods

AbstractAt the southern flank of the Vienna Basin, spectacular fold structures were exposed in the former Steinbrunn sand pit. The succession of Upper Pannonian age consists of decimeter- to meter-thick sandy, silty, and clayey beds, which are overlain by sandstone beds. Previously, these fold structures have been interpreted differently as of tectonic but also gravitational origin. To gain a more detailed insight into the 3D distribution and orientation of the folds, high-resolution geophysics such as electrical resistivity tomography (ERT), ground-penetrating radar (GPR), and electromagnetics (EM) were applied for mapping the subsurface in the surroundings of the sand pit. The EM results found that the uppermost layer was more clayey northwest and sandier southeast of the sand pit. To directly compare ERT and GPR results with the lithology of the fold structures observed in the sand pit, reference profiles behind the wall of the sand pit were performed. Both methods clearly revealed fold structures para...

Process-based investigations and monitoring of deep-seated landslides

Through the consolidation of alpine settlement areas there have been an increasing number of incidents in recent years related to the activity of landslides in Northern Tyrol (Austria). This has led to humans, buildings, and communication and transportation routes being increasingly threatened. In 1999 a rockfall event in Huben (Otztal, Austria) destroyed a wood mill and cut the main power supply for the inner Otztal. In the same year increased deformation rates at the Eiblschrofen (Schwaz, Austria) induced reoccurring rockfall events. In early summer 2003, parts of the deep-seated Steinlehnen rockslide system (Gries i. Sellrain, Austria) were reactivated, causing an acceleration of a sliding slab (Henzinger 2005). Secondary events in the form of increased rockfall activity were the direct consequence of these slope movements and demanded temporary evacuations and roadblocks as immediate measure. In order to protect the road and settlement area permanently a safety dam was built. After the floods in Tyrol in August 2005, parts of the complex Zintlwald landslide system (Strengen, Austria) accelerated. This was triggered on the one hand by increased water infiltration of the slope and on the other hand by intense fluvial erosion of the slope foot. As a consequence important supra-regional infrastructure such as sections of the Arlberg national road were destroyed. In addition, the possibility was given that a rapid landslide could dam the river Rosanna. Considering that a collapse of this dam would entail a sudden flood event downstream, a monitoring and warning system has been installed.