Plate motion near the fault gouge layer, and the elastic interplay between the gouge layer and the plate under stick-slip conditions, is key to understanding the dynamics of sheared granular fault systems. Here, a two-dimensional implementation of the combined finite-discrete element method (FDEM), which merges the finite element method (FEM) and the discrete element method (DEM), is used to explicitly to simulate a sheared granular fault system. We focus on investigating the influence of normal load, driving shear velocity and plate stiffness on the velocities and displacements measured at locations on the upper and lower plates just adjacent to the gouge in the direction parallel to the shear direction (x direction). The simulations show that at slips the plate velocities are proportional to the normal load and may be inversely proportional to the square root of the plate's Young's modulus; whereas the driving shear velocity does not show distinct influence on the plate velocities. During stick phases, the velocities of the upper and lower plates are respectively slightly greater and slightly smaller than the half of the driving shear velocity, and are both in the same direction of shear. The shear strain rate of the gouge is calculated from this velocity difference between the upper and lower plate during stick phases and thus the gouge effective shear modulus can be calculated. The results show that the gouge effective shear modulus increases proportionally with normal load, while the influence of shear velocity and plate stiffness on gouge effective shear modulus is minor. The simulations address the dynamics of a laboratory scale fault gouge system and may help reveal the complexities of earthquake frictional dynamics.

中文翻译：

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剪切颗粒断层系统中的板块运动

断层泥层附近的板块运动，以及粘滑条件下泥层与板块之间的弹性相互作用，是理解剪切粒状断层系统动力学的关键。在这里，结合有限元法 (FEM) 和离散元法 (DEM) 的组合有限离散元法 (FDEM) 的二维实现用于显式模拟剪切颗粒断层系统。我们重点研究法向载荷、驱动剪切速度和板刚度对在平行于剪切方向（x 方向）的上、下板紧邻凿槽的位置测量的速度和位移的影响。模拟表明，在滑动时，板的速度与法向载荷成正比，并且可能与板的杨氏模量的平方根成反比；而驱动剪切速度对板块速度没有明显影响。在粘滞阶段，上下板的速度分别略大于和略小于驱动剪切速度的一半，且剪切方向相同。凿子的剪切应变率是根据粘滞阶段上下板之间的速度差计算出来的，因此可以计算凿子的有效剪切模量。结果表明，凿槽有效剪切模量与法向载荷成比例增加，而剪切速度和板刚度对凿孔有效剪切模量的影响较小。模拟解决了实验室规模断层泥系统的动力学问题，可能有助于揭示地震摩擦动力学的复杂性。