Seismic noise measurements for the characterisation of Pays de Herve landslides

The Pays de Herve, located in the eastern part of Belgium, can be characterized as a multiple sections tableland with gentle slopes of less than 15°. It is located in the vicinity of the northern section of the Hockai Fault Zone, a 42 km-long seismogenic fault zone, that is characterized by the presence of fault scarps, multiple dissection elements and the presence of more than 20 paleo-landslides. Among these latter, the Manaihan landslide is the most studied and monitored landslide in the area. From a geological point of view, it developed in a Upper Cretaceous sedimentary setting, i.e., Vaals Clays overlaying Aachen sands. Even today, the slope is affected by instability and subsidence phenomena, likely linked to anthropogenic loading combined with prolonged periods of rainfall and possibly historic seismic events leading to liquefaction in the Aachen sands. Recently, new geophysical surveys have been carried out using an integrated approach, combining electrical resistivity measurements, active seismic methods (interpreted as P-wave tomography and MASW), and passive seismic techniques (single-station H/V). The key question to address is: How deep is the sliding surface, and is it possible to identify it?