The Maca landslide, located in the Colca Valley, in the Arequipa region is threatening the security of the village composed of around 800 inhabitants, the development of tourism in the Colca valley (160 000 tourists in 2009) and the pre-Inca heritages. The landslide real-time monitoring started in 2015 when 3 huts were built, 2 on the landslide and one on the rim the landslide, with continuous GPS and seismic measurements. Those data are also a key to study the combined effect of earthquakes and precipitations on the landslide kinematics. Preliminary results showing the response of the landslide to 2 major earthquakes are shown, and hypothesis regarding the associated mechanics are presented in this study.

In tectonically active mountain belts, landslides contribute significantly to erosion. Statistical analysis of regional inventories of earthquake-triggered-landslides after large earthquakes (Mw > 5.5) reveal a complex interaction between seismic shaking, landslide material, and rainfall. However, the contributions of each component have never been quantified due to a lack of in-situ data for active landslides. We exploited a 3-year geodetic and seismic dataset for a slow-moving landslide in Peru affected by local earthquakes and seasonal rainfalls. Here we show that in combination, they cause greater landslide motion than either force alone. We also show the rigidity of the landslide’s bulk clearly decreasing during Ml ≥ 5 earthquakes. The recovery is affected by rainfall and small earthquakes (Ml < 3.6), which prevent the soil from healing, highlighting the importance of the timing...