Decadal vegetation succession from MODIS reveals the spatio-temporal evolution of post-seismic landsliding after the 2008 Wenchuan earthquake

Strong earthquakes, especially in continental mountainous areas, can trigger extensive mass wasting, producing large amounts of debris that accumulates along the hillslopes or in drainage channels. The coseismic deposits and disturbed slopes are prone to be reactivated or remobilized by heavy rainfalls in the subsequent years after the earthquake. Predicting how long post-seismic landslide activity will return to the pre-earthquake level is a key to risk assessment and management. However, this is still poorly understood, and lacks quantitative prediction approach. The 2008 Wenchuan earthquake triggered an unprecedented number of landslides, creating an extraordinary natural laboratory to investigate the evolution of post-seismic landslides and their impacts on environment. Using the vegetation recovery rate as an indicator, we present the observational evidence of the post-seismic landslide evolution based on MODIS NDVI time series between 2000 and 2018. Using a simple vegetation recovery rate (VRR) function, we quantify the rate of vegetation regrowth in the Wenchuan earthquake affected area, and discuss the decaying trend of post-seismic landslide activities. Our findings show that 83% of the co-seismic landslides become inactive within a decade. The NDVI trend suggests that landslide activity may return to the pre-earthquake level within 18 years. The sensitivity of vegetation regrowth to post-seismic landsliding thus offers a great potential to improve our understanding of the spatio-temporal evolution of the post-seismic landslide activities.