用Burridge-Knopoff模型描述地震成核过程的动力学
Dynamics of earthquake nucleation process represented by the Burridge-Knopoff model
摘要：
基于一维Burridge-Knopoff（BK）模型，研究了地震成核过程的动力学。我们研究了模型在成核过程的各个阶段的性质，包括准静态初始阶段，不稳定的加速阶段和高速破裂阶段或主震。确定并研究了两种形核长度L_sc和L_c。形核长度Lsc和初始相只存在于弱摩擦不稳定区，而形核长度Lc和加速相则同时存在于弱和强不稳定区。结果表明，Lsc和Lc都由模型参数摩擦弱化参数和弹性刚度参数决定，与主震的大小几乎无关。滑动速度在初始阶段非常慢，直到L_sc，量级为板的拉动速度，而在加速阶段的某个阶段达到可检测的水平。讨论了结果的连续极限。BK模型的连续极限位于弱摩擦不稳定区，因此，在RSF定律下，成熟的均质断层总是伴随着准静态成核过程。检查成核过程的每个阶段的持续时间。弹性连续模型的关系和实际地震活动的影响进行了讨论。
英文摘要：
Dynamics of earthquake nucleation process is studied on the basis of the one-dimensional Burridge-Knopoff (BK) model obeying the rate- and state-dependent friction (RSF) law. We investigate the properties of the model at each stage of the nucleation process, including the quasi-static initial phase, the unstable acceleration phase and the high-speed rupture phase or a mainshock. Two kinds of nucleation lengths L_sc and L_c are identified and investigated. The nucleation length L_sc and the initial phase exist only for a weak frictional instability regime, while the nucleation length L_c and the acceleration phase exist for both weak and strong instability regimes. Both L_sc and L_c are found to be determined by the model parameters, the frictional weakening parameter and the elastic stiffness parameter, hardly dependent on the size of an ensuing mainshock. The sliding velocity is extremely slow in the initial phase up to L_sc, of order the pulling speed of the plate, while it reaches a detectable level at a certain stage of the acceleration phase. The continuum limits of the results are discussed. The continuum limit of the BK model lies in the weak frictional instability regime so that a mature homogeneous fault under the RSF law always accompanies the quasi-static nucleation process. Duration times of each stage of the nucleation process are examined. The relation to the elastic continuum model and implications to real seismicity are discussed.
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