Estimating Wenchuan Earthquake induced landslides based on remote sensing

On 12 May 2008 the magnitude 8.0 Wenchuan Earthquake erupted on the eastern fringe of the Tibetan Plateau in China, triggering many landslides onto towns and villages, leading to substantial loss of life and damage to property and the infrastructure. Local characteristic cloudy weather posed serious difficulties upon regional remote observation for disaster rescue in the mountainous region. To overcome weather limits to remote sensing, the study advanced one quick methodology to extract primary regional landslides with 8-day Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) and terrain slope information. The threshold of temporal NDVI jump (value of 0.4) was introduced to discriminate landslide induced sharp NDVI decline from seasonal variations of vegetation cover, while slope information can be used to further confirm land cover change caused by a landslide. The study indicated that the Wenchuan Earthquake induced about 170 km2 of landslides in the southern half of the Longmenshan Fault Zone, most of which was formerly covered by forest or shrub. An ecological restoration of the areas affected by landslides will therefore be quite difficult. In addition, the result emphasizes that regions with slopes over 15 degrees are exposed to high landslide risk, which should be carefully taken into account for settlement and transportation planning.