Multi-instrument geophysical monitoring of a km-scale slow-moving landslide in Nepal: Technical insights and preliminary results

Himalayan slopes are highly exposed to landslides, primarily triggered by earthquakes and monsoon precipitation. Satellite methods offer unrivalled spatial coverage of surface displacements on a weekly scale. However, they do not directly provide details of deformation at depth, nor do they offer sufficient temporal resolution to elucidate the continuity or intermittent nature of the landslide deformation during phases of heavy rainfall, strong rise in the water table or during intermediate seismic shaking. To address these issues in the context of the ANR/FNR project "SLIDE", we have recently deployed in late October 2025 a geophysical network at the level of one active, km-scale cultivated landslide in Nepal consisting in 16 co-located seismic and GNSS stations and one metereological station.

In this presentation, we will present the practical aspects of deploying and maintaining these instruments in remote Himalayan terrain. Each system required specific installation techniques and careful site selection to ensure stable measurements and long-term performance. Field operations were challenged by difficult access, variable road conditions, limited power availability, and unpredictable weather. Beyond technical challenges, community engagement is essential and close collaboration with local residents guided several site choices. We will also show the preliminary analysis of seismic, GNSS and meteorological data over the first 6 months of operation, which will be applied in the next three years to derive temporal and spatial changes of the landslide properties.