Preexisting faults exert a dominant control on frictional strength and stability of crustal faults. However, the complex interplay between fault and host rocks and their influences on frictional behaviors of fault zones remain poorly known. Here, we mimic natural fault-rock binary structures with rock-gouge assemblages made of fractured granite with or without gouge sandwiched inside. Then, we quantitatively assessed the frictional strength and sliding stability of the granite fractures by performing velocity stepping (VS) and slide-hold-slide (SHS) experiments. The VS results reveal a positive relationship between friction coefficient and velocity jump, indicating a velocity strengthening behavior. Besides, friction coefficient of fractured granite is found to be susceptible to gouge thickness and fracture roughness, while it is less affected by normal stress. According to the SHS experiment, frictional healing (Δ) is scaled logarithmically with hole time, this linear link is mainly caused by the logarithmic grow in contact area during the hold period. By comparing the pre- and post-shear surfaces, it is found that the fractures with rougher surface and thinner gouge layer suffer more severe damage in the post-shear surface, reflecting the dominant impacts of gouge and fracture roughness on the frictional sliding behaviors. Accordingly, three modes, namely fracture-surface-dominant, mix, and gouge-dominant modes, are proposed to characterize frictional sliding of fractured granite. Moreover, a threshold, termed as the critical gouge thickness, is identified based on frictional strength evolutions, exceeding of the critical gouge thickness will motivate the transitions of the sliding modes, and thus affect the frictional strength and stability. This study designed and conducted rock friction experiments, as a laboratory earthquake, on rock-gouge assemblages, the frictional strength and sliding stability of which were thoroughly explored, and therefore it shed light on the complex interplay of surrounding rocks with gouge in dominating the frictional properties of natural fault zones.

中文翻译：

---

模拟岩断层结构的摩擦强度和滑动行为：实验室研究

先存断层对地壳断层的摩擦强度和稳定性具有主导控制作用。然而，断层与围岩之间复杂的相互作用及其对断层带摩擦行为的影响仍然知之甚少。在这里，我们模仿天然断层-岩石二元结构，用破碎花岗岩制成的岩石-凿岩组合，内部夹有或不夹有凿岩。然后，我们通过速度步进（VS）和滑动-保持-滑动（SHS）实验定量评估了花岗岩裂缝的摩擦强度和滑动稳定性。 VS 结果揭示了摩擦系数和速度跳跃之间的正相关关系，表明速度强化行为。此外，裂隙花岗岩的摩擦系数易受凿痕厚度和裂隙粗糙度的影响，而受正应力的影响较小。根据SHS实验，摩擦愈合（Δ）与孔时间成对数关系，这种线性关系主要是由保持期间接触面积的对数增长引起的。通过比较剪切前和剪切后的表面，发现表面较粗糙和较薄的凿痕层的裂缝在剪切后的表面受到更严重的损伤，反映了凿痕和裂缝粗糙度对摩擦滑动行为的主导影响。因此，提出了三种模式，即断裂面主导模式、混合模式和凿岩主导模式来表征裂隙花岗岩的摩擦滑动。此外，根据摩擦强度演变确定一个阈值，称为临界划痕厚度，超过临界划痕厚度将激发滑动模式的转变，从而影响摩擦强度和稳定性。本研究针对岩-泥组合体设计并进行了实验室地震岩石摩擦实验，深入探讨了岩-泥组合体的摩擦强度和滑动稳定性，揭示了围岩与泥泥在主导摩擦力方面的复杂相互作用。自然断层带的性质。