Rain and small earthquakes maintain a slow-moving landslide in a persistent critical state

Landslides significantly contribute to erosion in tectonically active mountain belts. While statistical analyses of earthquake-triggered landslides reveal complex interactions between seismic shaking, landslide material, and rainfall, the individual contributions of each factor have remained unquantified due to a lack of in-situ data. This study utilizes a three-year geodetic and seismic dataset from a slow-moving landslide in Peru to show that the combined effects of local earthquakes and seasonal rainfall cause greater landslide motion than either force alone. The landslide's rigidity decreases significantly during larger earthquakes (MI ≥ 5), and recovery is hindered by rainfall and smaller earthquakes (MI < 3.6), highlighting the importance of the timing between these forcings.

Noélie Bontemps, Pascal Lacroix, Eric Larose, Jorge Jara, Edu Taipe