Seminar – Donat Fäh

Quantification of the seismic response of unstable slopes and its time variability

Landslides induced by earthquakes are among the major risks in the Alpine region. These include landslides in Alpine valleys and in lakes, the latter of which can lead to lake tsunamis. This risk has received little attention to date, partly because the underlying processes are complex and in parts poorly understood. In recent decades, the Swiss Seismological Service has developed various methods to address this issue. These include methods for characterising rock instabilities and sliding zones on mountain slopes and in lakes using geophysical and seismological techniques; seismic monitoring of dynamic behaviour; and modelling failure induced by earthquake excitation. The dynamic behaviour exhibits seasonal variations due to environmental influences (temperature, water and ice) as well as a continuous reduction in stability over years or decades. The various methods are presented using examples for Lake Lucerne and different rock instabilities, along with long-term monitoring of instabilities, one of which (Brinzauls) show striking changes in dynamic behaviour over just a few years.