Seismic and Resistivity Monitoring of Pont Bourquin Landslide in Switzerland

Landslides are natural and complex phenomena which can be encountered all over the world. They affect all types of geological formations and present a large variety of size, morphology and displacements rates. Among these phenomena, landslides in clay-rich formations are particularly complex due to the still unpredictable acceleration and fluidization that characterize them. In order to better understand this solid-fluid transition, the Pont Bourquin landslide in Switzerland has been continuously monitored with at least two vertical seismic sensors since the beginning of 2010, and 36 electrodes since the beginning of 2014 to assess the resistivity changes at different locations of the landslide. Relative velocities changes processed from ambient noise correlation show seasonal fluctuations between −2 and +2 % along the years. Only one drop of more than 7% was observed in summer 2010 preceding a major earthflow, showing that daily dV/V processing could be used as a precursor signal for landslide activation. Resistivity measurements show that certain parts of the landslide undergo strong electrical changes for which the causes are not yet determined. Because of the structural complexity of the landslide, further studies are requested to better understand the coupling between geophysical soil properties and environmental parameters.