动态应力作用与地震机制的初步研究

运用三维非线性动态有限元计算仿真方法研究了动态应力的作用及其与地震机制的关系. 结果表明地震产生的冲击力在加载与卸载过程中形成的应力波，在遇断层时多次反射并发生半波损失，反射的应力波叠加或干涉而形成的动态应力使围压减小和波动. 地震动态应力使围压产生低值波动，一方面使围压减小、摩擦力减小；另一方面，使裂纹串通、介质松动、接触面变平，降低摩擦系数、减小剪切强度. 由此均导致抗剪强度降低，从而触发地震. 动态应力作用时间短，触发地震大小与动态应力大小成正比、与距离成反比，触发地震位置、过程与孕震体断层产状有关.

A preliminary study on effects of dynamical stress in relation to earthquake mechanism

We use the three-dimensional nonlinear finite element method to perform a modeling study on effects of dynamical stress and its relation to earthquake mechanism. The result the shock force of earthquakes during processes of loading and unloading shows that stress wave is generated by .When this wave encounters a fault, it is reflected many times, causing haft-wavelength loss. The dynamical stress produced by superposition or interference of reflected stress wave makes confining pressure reduce and change at low values. On the one hand, the declined confining pressure reduces friction on the fault surface. On the other hand, the changing confining pressure brings about crack linkage, medium loosing, contact interface flattening, friction coefficient dropping, and shear strength reducing. These effects can trigger earthquakes. The affecting time of the dynamic stress is short. The magnitude of the event triggered by this stress is proportional to the size of the stress and inversely proportional to the distance. And the location and processes of the triggered earthquake are associated with the occurrence of the causative fault.