Cause-effect models of large landslides

Within the scope of the International Decade of Natural Disaster Reduction (IDNDR), cause-effect models of large landslides are being developed to estimate hazard. This work is based on a structural exploration of the landslide areas mainly by seismic methods. Information about the status of deformation is obtained by comparison of the actual topography with a reconstruction of the original topography, by GPS, and by SAR interferometry. Geologic and geomorphological evidence, as well as relevant information from other geo-scientific disciplines, is considered. The Finite Element Method is used to model the initial phase of a mass movement. Later on this modeling will be extended to the quasi-stationary creep phase and the transition from creeping to rapid sliding. Four large landslides within the crystalline rocks of the Eastern Alps have been investigated since 1997. Two of them are evaluated so far, and are presented in this paper. The largest one is the Kofels landslide with a total volume of 3.9 km(3) and a potential energy release of 5 x 10(16) Joule. Refraction and reflection multi-component seismic techniques were used to resolve structure and elastic parameters of the landslide masses. For the modeling of the initial phase of the landslides by the Finite Element Method a strain softening behavior of the rock mass has been assumed. The development of softened or fractured zones was successfully simulated, in agreement with the structures obtained by the seismic measurements.