Stick–slips are spontaneous, unstable slip events during which a natural or man-made system transitions from a strong, sticking stage to a weaker, slipping stage. Stick–slips were proposed by Brace and Byerlee (Science 153:990–992, 1966 ) as the experimental analogue of natural earthquakes. We analyze here the mechanics of stick–slips along brittle faults by conducting laboratory experiments and by modeling the instability mechanics. We performed tens of shear tests along experimental faults made of granite and gabbro that were subjected to normal stresses up to 14.3 MPa and loading velocities of 0.26–617 µm/s. We observed hundreds of spontaneous stick–slips that displayed shear stress drops up to 0.66 MPa and slip-velocities up to 14.1 mm/s. The pre-shear and post-shear fault surface topography were mapped with atomic force microscopy at pixel sizes as low as 0.003 µm 2 . We attribute the sticking phase to the locking of touching asperities and the slipping phase to the brittle failure of these asperities, and found that the fault asperities are as strong as the inherent strength of the host rock. Based on the experimental observations and analysis, we derived a mechanical model that predicts the relationships between the measured stick–slip properties (stress-drop, duration, and slip-distance) and asperity strength.

中文翻译：

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沿脆性断层粘滑的粗糙失效控制

粘滑是自发的、不稳定的滑移事件，在此期间，自然或人造系统从强的粘着阶段过渡到较弱的滑移阶段。粘滑是由 Brace 和 Byerlee (Science 153:990–992, 1966) 提出的，作为自然地震的实验模拟。我们在这里通过进行实验室实验和对不稳定力学建模来分析沿脆性断层的粘滑力学。我们沿着由花岗岩和辉长岩制成的实验断层进行了数十次剪切测试，这些断层承受了高达 14.3 MPa 的法向应力和 0.26-617 µm/s 的加载速度。我们观察到数百个自发粘滑，其剪切应力下降至 0.66 MPa，滑移速度高达 14.1 mm/s。剪切前和剪切后断层表面形貌用原子力显微镜以低至 0.003 µm 2 的像素大小绘制。我们将粘附相归因于接触粗糙体的锁定，将滑动相归因于这些粗糙体的脆性破坏，并发现断层粗糙体与主岩的固有强度一样强。基于实验观察和分析，我们推导出了一个力学模型，该模型可以预测测得的粘滑特性（应力降、持续时间和滑移距离）与粗糙强度之间的关系。