断层面形貌几何特征与破裂过程的相关性研究

"Asperity" or "obstacle" on a fault surface in deep, which controls and affects the all rupture process, has been deduced from the pattern of co-seismic displacements on fault surface. Then, what is the asperity or obstacle? What geologic implication does it have? Is it a real geometric structure, or only different stress field on the fault? What relationship between the "asperity" or "obstacle" and the geometrical features of the rupture zone on surface is there? To resolve these problems and understand "asperity" or "obstacle" deeply, a further study on the "relationship between morphologic characteristics of a fault surface and rupture process" should be done. First, using the study methods and mathematic models achieved in "study on high-resolution digital topography of fault surface (40872128)", we will calculate the roughness of a surface rupture and the co-seismic displacements along the rupture, and analyze their relevance. Second, combined with the experiment of stick sliding, we will study the relationship between the topographic features of the friction surface and the stress and strain field, micro-fracture distribution in unstable sliding process, and analyze how does the topographic features of the friction surface control and affect the unstable sliding based on the analysis of the topographic features of the friction surface, stress and strain field, micro-fracture distribution in different sliding stages. Finally, based on these results, we will probe the geologic implication of the "asperities" or "obstacles", and the relationship between the geometric features of a surface rupture and the "asperities" or "obstacles" on the fault surface in deep.

地震学家根据地震滑动位移分布推断断层面上存在与破裂过程相关的"凹凸体"或"障碍体"。那么，这些"凹凸体"或"障碍体"究竟是什么? 具有什么样的地质意义? 是断层面上确实存在的几何构造体，还仅仅是一种力学状态的差异? 又与破裂带的几何结构之间存在什么样的联系? 本项目将在"高精度断层面形貌学定量研究（40872128）"的基础上，开展地震破裂带几何结构特征与同震位移分布的相关性研究；结合失稳摩擦实验，研究失稳摩擦面微形貌特征与失稳滑动过程中的应力、应变场和微破裂分布的相关性，并分析破裂面形貌特征对破裂过程的影响和控制。最终，根据破裂面宏观形貌与破裂分布相关性和破裂面微观形貌与破裂过程相关性的研究结果，探索"凹凸体"或"障碍体"的地质意义，以及与破裂带地表几何结构之间的联系。

本课题通过开展地表破裂几何结构特征与同震位移分布的相关性研究，发现了相比于倾滑型地震，走滑型地震地表破裂的几何结构特征与同震位移相关性更高，表明走滑型活动断层（破裂）的几何结构特征在断层分段时更具有参考价值，4种断层几何特征指标与同震位移的相关程度依次是：阶区>走向变化>粗糙度>复杂度；开展了同震地表破裂与活动断层迹线几何形貌学特征研究，发现了两者的能谱密度曲线均具有的3分段特征，3种类型的同震地表破裂迹线的粗糙度存在差异：逆冲型>正断型>走滑型；课题组以山西霍山山前断裂上的断层面为例，使用变差函数法计算了断层面粗糙度分布，结果显示断层面形貌在倾向上具有分带性，该结果可确定3次地震活动次数与每次地震的同震位移约量3.5米，通过基岩断层面形貌特征识别断层活动历史信息的技术弥补了因在基岩区无法实施古地震探槽而无法进行断层活动历史定量分析的弊端；研发第二代高精度断层面形貌激光测量系统一套，为微观断层面形貌测量奠定了基础。