汶川Ms8.0级地震滑坡的长期活动性及趋势研究

After 2008 Ms8.0 Wenchuan earthquake, the frequency and scale of geo-hazards has a considerable increase comparing with before earthquake in the earthquake-hit area, which has brought an adverse impact on the infrastructures and human safety. So far, for the long-term activity of post-seismic geo-hazards, the linear index of sustained time has been extensively studied while the variation of spatio-temporal distribution has not been well addressed. So, the long-term landslides from 2000 to 2018 will be taken to conduct the study on the long-term activity characteristics of landslide in the meizoseismal area, which is mainly focused on the spatio-temporal variation pattern before and after earthquake. The adopted methods include spatial analysis using GIS technology, statistical probability analysis and multiple-temporal remote sensing, etc. The study mainly includes 3 aspects: (1) variation pattern of landslide spatial distribution, (2) variation pattern of landslide intensity over time series, and (3) variation pattern of landslide intensity-frequency distribution. In spatial, focusing on the study on the relationship of priority interval of causal factors and spatial clustering of landslides under the sustained effect of earthquake. In temporal, focusing on the study on two landslide intensity correlating with time: landslide number of one day, landslide number of one rainfall event. Then, analyzing the mechanism of sustained effect of earthquake on development characteristics of post-seismic landslides, and quantitatively describing the long-term activity characteristics of landslides in the earthquake-hit area, and inferring their future development tendency. The study results can provide the beneficial reference for hazard assessment and risk control of post-seismic landslides.

汶川地震之后，地震灾区地质灾害加剧，频率和规模显著高于震前水平，对震后工程规划建设具有重大影响。针对当前地震地质灾害的长期活动性研究主要集中于“时间”这一线性指标、缺乏“时空分布”变化规律研究的现状，本项目拟以汶川Ms8.0级地震前后滑坡灾害的时空变化为切入点，在完善长时间序列地震滑坡数据库（2000-2018）的基础上，采用GIS空间分析、数理统计和遥感监测等方法，开展汶川震区滑坡的长期活动性研究。重点揭示汶川震区滑坡在空间上的发育分布变化规律、在时间上的强度变化规律以及强度-频率分布变化规律。通过地震影响下的滑坡优势因子区间与空间集聚性的关系研究以及两种与时间相关的滑坡强度（DL、RL）研究，剖析地震效应对汶川震后滑坡长期发育分布特征的影响机制，定量描述汶川震区滑坡的长期活动性，并推断其发展趋势。研究成果可以为汶川震后滑坡危险性评价和风险管控提供科学依据。

针对强震区震后地质灾害强度显著增加的科学问题，以汶川震区为主要研究区，开展了强震区滑坡的长期活动性研究，揭示了强震区滑坡时空变化规律，定量描述了强震区滑坡的长期活动性；建立了考虑地震后效应的强震区地质灾害评价思路，完成了活动断裂带潜在地震诱发滑坡危险性预测评价。取得如下主要成果：.（1）总结了地震滑坡长期活动性的国内外研究进展，开展了汶川震区典型地质灾害野外地质调查，补充完善了强震区长时期滑坡数据库；汶川震区震后5年的地质灾害总体频率明显增长，其中泥石流频率增长最大，然后是崩塌和滑坡。.（2）相对于震前，地震效应改变了滑坡空间分布的优势因子区间，震前、同震和震后滑坡空间分布的优势坡度区间分别为30-35°、50-60°和35-40°；地震效应增加了滑坡强度变异性，也增加了较高滑坡强度的概率密度。.（3）采用概率密度方法深入研究了强震区滑坡面积-频率分布规律，推断滑坡面积-频率分布与环境因子的正相关关系为：滑坡面积变异性与震级、地震烈度、高程和坡度，最大概率滑坡面积与震级、高程、坡度。.（4）推测地震后效应影响下的高滑坡活跃性将在震后持续约10年左右，震后10-23年是地震后效应影响下的低滑坡活跃性阶段，之后的滑坡活跃性可以基本不考虑地震后效应的影响，是地震后效应的缓慢消失阶段。.（5）提出了考虑地震后效应的地质灾害易发性综合评价思路，基于传统信息量模型和Logistic逻辑回归模型，建立了加权信息量模型，并完成了青藏高原东缘地质灾害易发性综合评价。.（6）获得了适应于鲜水河断裂带区域地震地质背景的Newmark模型参数，完成了鲜水河断裂带潜在地震诱发滑坡危险性预测评价，地震滑坡高危险区域以震中为中心，沿断裂带呈椭圆形分布。