Earthquake-triggered landslides in Switzerland: from historical observations to the actual hazard

Donat Fäh, Jan Burjanek, Carlo Cauzzi, Remo Grolimund, Stefan Fritsche and Ulrike Kleinbrod

The building inventory in the Alpine area multiplied over the last century, increasing exposure to potential earthquake impacts. This is particularly critical in relation to earthquaketriggered mass movements. In Switzerland, it is possible to assess the spatial extent and impact of such secondary earthquake effects from historical and paleo-seismological analysis of past damaging earthquakes. After calibration against observations of these events, scenario modelling has been recently implemented within ShakeMap, a tool applicable to near real-time estimates. The spatial resolution could be improved using additional information like rock-slope hazard maps or detailed studies on particular unstable slopes. In order to improve our understanding of the dynamic response of unstable rock slopes, an extensive measurement campaign is presently being performed to determine eigenfrequencies, groundmotion polarization and amplification features, and to estimate the volume of the instability. A semi-permanent seismic installation was set up at the Alpe di Roscioro (Preonzo) site, a slope that is close to collapse, to continuously monitor seasonal variations of its dynamic behavior and how it changes over time.

2016/1 249-256