Swiss alpine valleys project

Settlements only few hundred meters apart can be affected at significantly different levels by the same earthquake. The cause is the local earthquake response, or site amplification, which is determined by the type of soil (e.g. soft sediments or stiff rock) but also by its geometry (a vast plain or a sedimentary basin). In this perspective, the alpine valleys are peculiar geological environments, as the thickness of the sedimentary infill increase from few meters at the margins of the valley bottom to several hundred meters at its centre; this setting determines distinctive earthquake response effects. Besides, valleys are not marginal from the risk point of view, as they can be densely populated and host critical infrastructure for the transport of goods and people across the alpine arch.

In 2019, the earthquake working group of the SIA 261 commission has therefore recommended the execution of a baseline study on the topic of earthquake local response in alpine valleys. later included in the federal measures for earthquake risk management (BAFU, 2020). This research project directly addresses such recommendation; it aims i) at a systematic investigation of amplification effects of seismic waves in the alpine valleys of Switzerland and ii) at the development of a proposal for their consideration in the next revision of the SIA 261 building code.