基于实验结果讨论断层破裂与强震物理过程的若干问题

A DISCUSSION ON RELATED ISSUES OF PHYSICAL PROCESS OF FAULTING AND STRONG EARTHQUAKE BASED ON EXPERIMENTAL RESULTS

基于断层摩擦滑动实验、含凹凸体断层的变形破坏实验、断层撕裂扩展的实验、交叉断层的变形实验等多种实验结果并结合前人的工作 ,讨论了与断层破裂与强震物理过程相关的若干问题。研究表明 ,断层的整体滑动引起其两侧块体弹性应变的释放 ,是强震发生的原因 ,因此构造活动区具有较大尺度、结构连续且简单、介质均匀的断层 (或断层段 )是产生强震必备的构造条件 ,深部新生断层(盲断层 )向上撕裂扩展产生强震 ,尚需“弱层”提供“解耦”条件以便断层发生整体滑动。强震孕育过程中包含着凹凸体的破裂 ,断层面上凹凸体的尺度、强度及数量决定着前震活动的特征、强震动态破裂过程以及前兆现象。由断层分割的块体通过边界断层的交替滑动、以“框动”的方式运动 ,因此块体周边的断层上强震活动具有交替性。

This paper discusses the related issues of physical process of faulting and strong earthquake based on a series of experimental results, including the frictional sliding of faults, the deformation of faults containing asperities, the tearing propagation of faults, and the deformation of intersecting faults, and in combination with previous works. The analysis indicates that a strong earthquake is caused by the slip of entire fault, which brings about the rapid release of elastic strain in the rock blocks; therefore, a fault (or a segment of fault) with considerable scale, with continuous and simple geometry, and with homogeneous media in an active region of tectonics is the necessary condition for occurrence of a strong earthquake. For occurrence of a strong earthquake during tearing upward of a newborn fault in deep depth (blind fault), a “weak” layer is needed to play a role of “uncoupling” for the slip of entire fault. The preparation and nucleation of a strong earthquake involve fracturing of asperities on the fault plane, and the foreshock activity, the dynamic rupture process and the precursors of the strong earthquake depend on the scale, the strength and the number of asperities. The movement of a fault block is characterized by the alternate slips along its boundary faults; so strong earthquakes occur alternately in the boundary faults of the block.