断层自发破裂传播的数值模拟:速率状态摩擦定律本构参数的影响

地震往往受控于滑动面的摩擦性质,这种摩擦性质可以由速率状态摩擦定律较好地描述.速率状态摩擦定律中的本构参数a和b与动态摩擦系数相关,从而影响着同震位移与剪切应力的时空演化.本文在前人工作的基础上,采用三维边界积分方程法模拟速率状态摩擦定律控制下均匀全空间中平面断层的自发破裂传播过程,并详细讨论了a和b对滑动速率、剪切应力和破裂传播速度的影响.数值结果表明a和b的不同取值将导致不同的破裂行为,b－a的值越大,断层越不稳定,这种不稳定性有利于裂纹的产生与扩展.但滑动速率的时空分布不只依赖b－a,而且还与a和b的具体取值有关,断层面上滑动速率峰值与剪切破裂强度均随着a的减小而增大,随着b的增大而增大.相关结果有助于加深对断层自发破裂传播的认识.

Numerical simulation of spontaneous rupture propagation: dependence on constitutive parameters in rate- and state-dependent friction laws

Most earthquakes are controlled by the frictional property of the sliding surface, which could be well described by rate- and state-dependent friction laws. Constitutive parameters of these friction laws, a and b, are related to the coefficient of kinetic friction. They affect significantly the spatio-temporal evolution of co-seismic dislocation and shear stress. In this study, we present a 3D boundary integral method to simulate the spontaneous rupture propagation under the rate- and state-dependent friction laws on a planar fault in an elastic full space. We also discuss the effect of a and b on slip rate, shear stress and rupture speed, respectively. The simulation results showed that rupture behaviors strongly depend on the parameters of a and b. The instability of faults is enhanced by the increase of b－a. Such increasing instability could lead to a rupture easily. The slip rate and the shear stress depend not only on b－a, but also on the values of a and b themselves. Both the peak slip rate and the shear strength increase with a decreasing a or an increasing b. This study may strengthen the understanding of the spontaneous rupture propagation of faults.