A study on interaction of asperilies based on laboratory and numerical experimets

基于两自由度块弹簧模型和大型双轴实验，研究了板边界上的多种滑移模式。滑动实验是在已有100厘米断层面的大型花岗岩块上进行的。在断层长度的一半上，通过插入一个薄的特氟龙片，可以得到速度增强的摩擦，而另一半则保留了裸露岩石表面的速度减弱摩擦。在等速加载下，在速度弱化区发生动态粘滑重复，在速度强化区发生后滑。速度增强区的同震滑动也较小，且随距离速度减弱区的距离增加而减小。实验室实验中观察到的行为通过二自由度块-弹簧模型进行定量模拟，其中两个块（Block 1和Block 2）由一个线性弹簧连接，由一个缓慢移动的驱动器驱动。假定各块间的摩擦均服从速率和状态相关的摩擦规律。假设a-b在区块1为负，在区块2为正，则区块2发生余震。该模型还可以再现在板块边界上观测到的宽谱滑移模式，包括偶发性慢滑移。

We studied various slip modes on a plate boundary on the basis of a two-degree-of-freedom block-spring model and large-scale biaxial experiments. Slip experiments were conducted using large granite blocks with a pre-existing fault surface of 100 cm in length. Velocity-strengthening friction was given over a half of the fault length by inserting a thin Teflon sheet, while the other half retained velocity-weakening friction of the bare rock surface. Under a loading at a constant velocity, dynamic stick-slip repeated on the velocity-weakening region, causing afterslip on the velocity-strengthening region. The velocity-strengthening region experienced small coseisic slip as well, with the magnitude decreasing with the distance from the velocity-weakening region. The behaviors observed in the laboratory experiments were quantitatively simulated by a two-degree-of-freedom block-spring model, in which two blocks (Block 1 and Block 2) are connected by a liner spring and driven by a slowly moving driver. The friction on each block was assumed to obey rate and state dependent friction law. When a-b was assumed to be negative for Block 1, and positive for Block 2, afterslip occurred at Block 2. This model can also reproduce wide spectrum of slip modes observed on a plate-boundary, including episodic slow slip.