地震诱发滑坡危险性评估的高分辨率并行有限元数值试验分析与遥感影像校正

Landslide triggered by earthquakes is an import influencing factor for working out a plan of emergency rescue after the earthquake. Assessment of landslides triggered by large earthquake is an one of the key scienctific issues deserving to be solved immediately. According to the existing research on the landslides, we employ finite element method incorporated with large-scale parallel computing technology to work on quickly census calculation and preliminary assessment for the landslides triggered by Wenchuan earthquake through theorectical analysis and verification exploration. Our main research contents include: 1) Constructing a 3D layered model with million meshes incorporated with high accuracy digital elevation model and earthquake fault parameters using unstructured gridding technique, building co-seismic deformation model and seismic wave propagation model using parallel finite element method incorporated with the gravity and tectonic stress based on the theory of elastic mechanics, and making research on the characteristics of the stress field triggered by Wenchuan earthquake from the two models. 2) According to the basic theory of landslides mechanism, building a criterion for landslides risk based on the Coulomb failure criterion, and taking assessment research on our calculation. 3) Taking comparison of our calculation with the remote sensing images received after Wenchuan earthquake and the field investigation, to verify the reliability and scientificity of our numerical results, and finally taking modification of our numerical model. After a giant earthquake, some data such as remote sensing image has not yet been obtained, and geological environment of the disasters is bad for people reaching quickly. We can in time take preliminary assessment on the landslide disasters using our calculation model to provide possible landslide danger point in macroscopically considered. The calculation can provide first-hand quantitative reference information and scientific basis for immediately earthquake-induced landslides evaluation, emergency rescues, and decision guidance.

大地震发生后的滑坡灾害评估是我国地震学和地球动力学领域亟待解决的关键性科学问题之一。项目将借助于高分辨率并行有限元数值模拟手段，结合现有滑坡灾害的研究成果，以汶川大地震后的实际滑坡灾害为研究对象，通过理论分析和实践验证，进行探索性尝试，开展宏观上地震诱发滑坡危险性的普查计算与评估预测研究，并与高分辨率遥感影像进行对比矫正。主要研究内容包括: 1）融合震前高精度地形数据、发震断层参数和关键性物性参数，基于弹性力学理论，考虑重力及构造应力场作用，构建百万量级网格的三维非结构化网格数值模型，研究同震形变和地震强地面运动产生的近地表应力场分布特征；2）结合现有滑坡力学基本理论，基于库仑破裂准则，建立滑坡危险性的判断准则，开展评估研究；3）结合震后高分辨率航空遥感影像资料，开展模型评价、验证与优化研究，修正和改进关键性模型参数和数值模型。可预见的研究成果可以为指导震后抗震救灾工作提供重要的科学依据。

通过对震后遥感影像资料解译来综合分析地震滑坡灾害分布规律及其与各种影响因子的关系，虽不受时间和地域限制，但较难真正的考虑地震本身的动力触发机制。利用地震动参数对区域性地震诱发滑坡危险性的定量分析法，易受实际地震观测台站和记录数据缺乏的限制。.本项目以汶川大地震为研究对象，基于已有关于汶川地震震源破裂机制及过程研究成果，成功的实现了汶川地震有限断层模型的几何构建与定量参数化，研究构建了三维弹性的并行有限元数值模型，完成了汶川地震诱发区域静态同震形变特征的模拟计算，并与已有关于遥感影像资料解译得到的滑坡分布特征进行了对比分析，发现同震形变分布特征与滑坡分布特征有很好的一致性，明显受汶川地震有限断层破裂过程控制。进一步的，融合震前高精度数字高程模型，研究构建了区域的三维弹性的地震强地面运动的数值模型，实现了汶川地震强地面运动引起的形变场及应力变化的动态模拟，并对地震动峰值参数与滑坡分布特征进行了对比分析。基于地理信息系统平台，对汶川地震震后航空遥感影像光学资料进行了处理并生成了产品数据，特别对北川县及其县城的滑坡灾害进行了遥感解译和信息提取，以及对龙门山断裂带区域地质地貌与断层分布特征进行了遥感分析研究，为深入认识汶川地震诱发滑坡分布规律提供了参考依据。在此基础上，以北川县城的新中滑坡为研究对象，研究构建了真实的三维并行的精细模型，基于库仑破裂准则，成功的模拟了新中滑坡的动态失稳特征和发展过程，并将数值计算结果与震后高分辨率航空遥感影像资料及野外实地考察资料进行了对比分析，发现数值计算得到的滑坡失稳面与震后实际滑坡面有很好的一致性，验证了数值模型的可靠性，进一步对比研究显示，地震载荷效应对滑坡稳定性存在明显的扰动作用，坡体上部的拉伸破裂对滑坡失稳存在主导作用，坡体地形坡度是地震诱发滑坡危险性的关键因素之一。.研究成果为地震诱发滑坡危险性的评估预测提供了一种定量化的研究平台和新方法。

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