Temporal And Spatial Differentiation In The Surface Recovery Of Post-Seismic Landslides In Wenchuan Earthquake-Affected Areas

Catastrophic earthquakes that occur in mountainous areas always trigger a large number of co-seismic geohazards, which exerts a negative impact on the geological environment and the vegetation coverage. The violent destruction of vegetation and a large number of loose material sources caused by the Wenchuan earthquake led to a sharp drop in the rainfall threshold of the landslide and debris flow in the strong earthquake areas. The surface recovery of post-seismic landslides can indicate the active trend of landslides and debris flows, which is of significance to understand when the geohazard risk lasts after the Wenchuan earthquake. Existing studies on the long-term effect of the Wenchuan earthquake are mainly aimed at a large scale, detailed analysis of differences in the change of geohazard activities and vegetation recovery at a small scale is quite lacking in different regions. To fill this substantial knowledge gap, we selected three typical regions (Wenchuan region, Beichuan region and Qingping region) along the Wenchuan earthquake generated fault as the study area to investigate the temporal and spatial differentiation of surface recovery at post-seismic landslides. Firstly, we identified the multi-temporal active landslides based on NDVI data and quantified the changes in the active landslide area, and also analyzed the controlling factors of landslide activity. Afterwards the natural vegetation recovery at co-seismic landslide sites was analyzed. The results suggests that the strong earthquake causes more damage to hard rock areas than soft rock areas, and post-seismic landslides located in high and steep terrain are more likely to be reactivated, and the surface recovery rate is slower. The recovery rates of the average NDVI after the earthquake in the Wenchuan area, the Qingping area and the Beichuan area were 0.024/year, 0.033/year, and 0.037/year, respectively. The surface recovery rates at post-seismic landslides in different regions were affected by geological factors and climate. NDVI values at post-seismic landslides in the Wenchuan area, Qingping area and Beichuan area would almost return to the pre-earthquake level in 16 years, 12 years and 11 years after the earthquake.