汶川地震灾区滑坡分布的变化规律及其驱动要素分析

Earthquake-triggered landslides could have important and long-lasting impacts on both geomorphic evolution and human society. The 2008 Wenchuan earthquake triggered thousands of hundreds of landslides, which significantly altered mountain environment. After this earthquake, landslides are very active, jeopardizing post-seismic reconstructions. However, there is a lack of long-term, time consistent study on the changes of these landslides in post-seismic years, hindering our understanding towards its changing trend and inherent mechanisms. In this project, we try to settle these problems in the 2008 Wenchuan earthquake affected mountainous region by collecting various kinds of optical earth observation data. Firstly, spatial distributions of landslides in all post-seismic years will be extracted based on semi-automatic landslide extraction algorithms from these remote sensing images and validated by field reconnaissance. These results will constitute a time series of landslide distribution maps, from which the spatial patterns of landslide changes will be analyzed. Secondly, key driving factors that may determine the spatial patterns of post-seismic landslide changes will be recognized and their possible mechanisms will be explored. Finally, quantitative models to predict future landslide area changes will be established based on homogeneous zones segmented by those key driving factors. The projected results could have significant importance to uncover the spatial-temporal processes of orogeny erosion and mitigate regional post-seismic disasters.

地震触发的滑坡对地貌演化和人类社会都有重要的影响。2008年汶川地震触发了大量的山体滑坡，显著改变了震后的山地环境。震后，滑坡不断活动，对灾后恢复重建构成重大威胁。然而，目前对灾区滑坡分布在震后的变化尚缺少长时间的连续研究，制约了对震后滑坡变化规律的理解。本项目拟以2008年汶川地震影响的山区为研究区，收集地震至今十余年的各类对地观测资料，采用半自动滑坡提取的方法和野外实地验证，获取灾区震后各年的滑坡空间分布，分析震后滑坡活动的空间差异；在此基础上，甄别导致震后滑坡活动性差异的关键驱动因素，探讨其作用过程；最后，依据关键驱动因素把研究区划分为同质的基本统计单元，并在每个基本单元里建立震后滑坡面积变化与距地震发生时间的定量模型。项目的预期成果有望揭示大震后的滑坡侵蚀变化过程和震后山地环境稳定性的变化规律，对山区震后的防灾减灾有重要的理论和现实意义。

发生在山地环境的大地震通过引发大量的山体滑坡，可显著的改变区域孕灾环境的稳定性，增加震后年份地质灾害的活跃程度。为了从长时间序列上连续观测灾区滑坡分布在震后的变化、增进对震后滑坡变化规律的理解，项目以2008年汶川大地震为例，采用多源遥感数据并结合野外实地验证研究了汶川地震影响的整个大区域的滑坡变化；采用更高时间分辨率的遥感影像研究了滑坡上的植被恢复过程；揭示了震后滑坡动态和滑坡上植被恢复的关系；探讨了大地震后各类影响因素对滑坡活动性的影响。研究结果表明，1)震后年份滑坡面积的减少和滑坡上植被的恢复非常相关，滑坡上植被的恢复可作为滑坡面积减少的有效代用指标；2)地震引发的同震滑坡在震后年份整体快速减少，但是空间变化上存在明显的差异性，其中震中低海拔的岷江河谷两岸地区的地震滑坡消失（主要变现为滑坡被植被覆盖）的最快、龙门山高山区的高海拔滑坡恢复的最慢，以至于汶川地震12年后很多滑坡仍然可见；3)海拔、坡位和地震前的植被生长状态是造成震后滑坡变化存在空间差异的主要影响因素。项目的实施增进了对山地大地震后灾害演化规律的认识，对防灾减灾和灾后恢复重建有一定的意义。