SUMMARY

The effects of fault waviness on the fault slip modes are unclear. Laboratory study on the effects of the centimeter-scale fault contact distribution, which is mainly controlled by the fault waviness, on granodiorite stick-slip instabilities may help to unveil some aspects of the problem. The fast and slow stick-slip motions were separately generated in two granodiorite samples of the same roughness but different fault contact distributions in the centimeter scale in the laboratory. The experimental results show the following: (1) the fault with the small contact area and heterogeneous contact distribution generates fast stick-slip instabilities, while the fault with the large contact area and homogeneous contact distribution produces slow stick-slip events; (2) the nucleation processes of the fast stick-slip events are characterized by abrupt changes once the nucleation zones expand to the critical nucleation length that is observed to be shorter than the fault length, while the slow stick-slip events appear as a gradual evolution of the nucleation zones leading to total fault sliding. These indicate that, unlike the micron-scale fault contact distribution controlled by roughness, which depends on the grain size of the abrasives used for lapping the fault surface, the centimeter-scale fault contact distribution, which depends mainly on the waviness of the fault surface profile, also plays an important role in the fault slip modes. In addition, the effects of the fault waviness on the fault friction properties are preliminarily analyzed based on the rate- and state- dependent friction law.

中文翻译：

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断层起伏对花岗闪长岩粘滑不稳定性影响的室内研究

概要

波纹度对断层滑动模式的影响尚不清楚。对主要由断层波纹度控制的厘米级断层接触分布对花岗闪长岩粘滑不稳定性影响的实验室研究可能有助于揭示该问题的某些方面。在实验室中，粗糙度相同但断层接触分布不同的两个花岗闪长岩样品分别产生了快速和缓慢的粘滑运动。实验结果表明：（1）接触面积小，接触分布不均匀的断层产生快速的粘滑不稳定性，而接触面积大，接触分布均匀的断层产生较慢的粘滑事件。（2）快速成核过程的成核过程的特征在于，一旦成核区扩展到临界成核长度（观察到比断层长度短），突变就会突然发生，而缓慢成层的粘滑事件则是逐渐形成的。成核区的演化导致总断层滑动。这些表明，与粗糙度控制的微米级断层接触分布不同，后者取决于用于研磨断层表面的磨料的晶粒尺寸，而厘米级断层接触分布主要取决于断层表面的波纹度轮廓，在断层滑动模式中也起着重要作用。此外，基于速率和状态相关的摩擦定律，初步分析了断层波纹度对断层摩擦特性的影响。