We discuss data of three laboratory stick-slip experiments on Westerly Granite samples performed at elevated confining pressure and constant displacement rate on rough fracture surfaces. The experiments produced complex slip patterns including fast and slow ruptures with large and small fault slips, as well as failure events on the fault surface producing acoustic emission bursts without externally-detectable stress drop. Preparatory processes leading to large slips were tracked with an ensemble of ten seismo-mechanical and statistical parameters characterizing local and global damage and stress evolution, localization and clustering processes, as well as event interactions. We decompose complex spatio-temporal trends in the lab-quake characteristics and identify persistent effects of evolving fault roughness and damage at different length scales, and local stress evolution approaching large events. The observed trends highlight labquake localization processes on different spatial and temporal scales. The preparatory process of large slip events includes smaller events marked by confined bursts of acoustic emission activity that collectively prepare the fault surface for a system-wide failure by conditioning the large-scale stress field. Our results are consistent overall with an evolving process of intermittent criticality leading to large failure events, and may contribute to improved forecasting of large natural earthquakes.

中文翻译：

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间歇性临界多尺度过程导致粗糙实验室断层上的大滑移事件

我们讨论了在提高围压和粗糙断裂表面上恒定位移速率下对西风花岗岩样品进行的三个实验室粘滑实验的数据。实验产生了复杂的滑移模式，包括带有大小断层滑移的快速和慢速破裂，以及断层表面上产生声发射爆发而没有外部可检测到的应力下降的故障事件。通过十个地震力学和统计参数的集合来跟踪导致大滑移的准备过程，这些参数描述了局部和整体损伤和应力演化、局部化和聚类过程以及事件相互作用。我们分解了实验室地震特征中复杂的时空趋势，并确定了不同长度尺度上不断变化的断层粗糙度和损伤的持续影响，以及接近大型事件的局部应力演变。观察到的趋势突出了实验室地震在不同空间和时间尺度上的定位过程。大型滑动事件的准备过程包括以有限的声发射活动爆发为标志的较小事件，这些事件通过调节大规模应力场来共同为断层表面做好系统范围的故障准备。我们的结果总体上与导致大型故障事件的间歇性临界性的演变过程是一致的，并且可能有助于改进大型自然地震的预测。