Combined effect of the Mw7.9 Gorkha - Mw 7.2 earthquakes sequence, and the 2015 monsoon on the triggering of rapid and slow-moving landslides.

Encadrants : Pascal Lacroix, Jean-Robert Grasso, Laurence Audin

Mots clés Thématiques et Méthodes : landslides, earthquake triggering, optical images, stereo images, DEM, image correlation

Lieu du stage : Isterre Grenoble

Contact email : pascal.lacroix univ-grenoble-alpes.fr

The two main earthquakes of April-May 2015 of magnitude Mw7.9 and 7.2 have caused a large number of casualties and destruction in Nepal. About 20% of the casualties results because of numerous co-seismic avalanches and landslides that triggered village burial.

Moreover earthquakes may have also, over several years, a major impact on landslides. Despite the societal importance of this phenomenon, the influence of seismic shaking on shallow bedrock fracturing and its increased sensitivity to landsliding remain insufficiently documented and quantified. The Gorkha earthquake provides therefore a rare opportunity to study the impact of a large continental earthquake combined with monsoons seasons on steep slopes destabilisation.

During this stage, we will measure topographic changes and the deforming hillslopes using differential high resolution DEMs, and subpixel correlation techniques, and making the physical link with rainfalls and major earthquakes.

All the data will be processed from high resolution stereo Pléiades images available on an area of 1200km2 at different dates. Inventories of rapid and slow-moving landslides will be realized and analyzed in regards with the seismic source parameters.