新疆富蕴断裂带枢纽运动的有限元数值模拟研究  

Finite Element Numerical Simulation on Pivotal Movement of Fuyun Fault Zone

作　　者：高翔[1,2] 邓起东[2] 陈汉林[1] 洪汉净[2] 

机构地区：[1]浙江大学地球科学系,浙江杭州310027 [2]中国地震局地质研究所,活动构造与火山重点实验室,北京100029

出　　处：《大地构造与成矿学》2015年第5期769-779,共11页Geotectonica et Metallogenia

基　　金：中国地震重点监视防御区活动断层地震危险性评价项目(财1521044025)资助

摘　　要：地震发生之前,变形是如何集中在一条断裂上或一条断裂的某一段落上,能否观测到在断裂错动发生大位移前,先形成的具有启动断裂快速错动传播的区域及其向失稳发展的物理过程,是大地震研究中极其重要的问题。对断裂走滑运动和走滑型地震而言,断裂枢纽运动正是断裂带上变形局部化和地震成核孕育的条件,认识这一运动过程和机制是认识走滑断裂上地震孕育、发生机制的关键之一。本文在前人工作的基础上,在野外对富蕴断裂带的枢纽运动特征进行了补充调查,主要对富蕴断裂带不同断层段的运动学特征的转换、枢纽轴部强烈挤压的逆掩断层和挤压透镜体的存在和特点进行了专门的观察,在此基础上,通过数值模拟方法模拟了富蕴活动断裂和地表破裂带主体枢纽运动。结果表明,断裂分段运动性质转换明显,其中枢纽轴部挤压性质强烈,走滑断裂的枢纽运动与矩形截面梁的扭转相似,表现出典型的掀斜特征;研究了影响枢纽运动的因素——断层面的倾角和闭锁区的面积,随着断层面倾角的减小,枢纽运动程度加深;随着断层面闭锁区面积的增大,枢纽运动明显受阻;探讨了断层面的应力状态,发现枢纽轴部是断层两盘发生升降的支撑点,是走滑断裂的闭锁区,是枢纽型地震的发震部位,并且在闭锁区及其附近存在一个应力集中区使得应力由外向内一直处于积累状态,反映了地震的成核过程。Deformation localization and earthquake nucleation are key issues in earthquake research. For both strike-slip movement and strike-slip type earthquake, pivotal movement of strike-slip fault is critical for deformation localization and earthquake nucleation. Recognition of this process and mechanism is essential to understand the seismogenic and occurrence mechanism of earthquakes in strike-slip fault zones. Based on previous researches, we discuss the issues concerning deformation localization and earthquake nucleation in strike-slip processes by using a pivotal movement model. To investigate the pivotal movement in the Fuyun fault, we analyzed the fracture characteristics of the fault segment transformation, the strong compression of the pivotal axis in an overthrust fault, and the existence and characteristics of the lens. Moreover, combined field investigation and numerical simulation is used to further analyze pivotal movement. Through analysis, the following conclusions can be inferred： （1） The pivotal movement of a strike-slip fault is similar to torsion of the rectangular beam section, which is typically tilted. The pivotal axis upon which the earthquake occurred is the strong point of the lifting movement of the two walls and the block region of the strike-slip fault. In this region, compression is the most intense during the entire stage of pivotal movement, and the stress is localized and released.（2） Two factors influencing pivotal movement include the dip angle of fault plane and the area of the block region. When the dip angle increases, vertical displacement also increases and results in tilting. When the area of the block region increases, vertical displacement decreases, and tilting is blocked. （3） Stress on the fault plane centralizes from all directions to the block region. With the accumulation of stress, the outside inward stress centralization continues, which results in the ever enlargement of the stress centralization area. The most intensive stress always occurs in the core

关 键 词：枢纽运动 变形局部化 地震成核 数值模拟 富蕴断裂带 

分 类 号：P315[天文地球—地震学] P542[天文地球—固体地球物理学]