Intermittent lab earthquakes in dynamically weakening fault gouge
Intermittent lab earthquakes in dynamically weakening fault gouge
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DOI：
10.1038/s41586-022-04749-3
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发表时间：
2022-06
期刊：
影响因子：
64.8
通讯作者：
V. Rubino;N. Lapusta;A. Rosakis
中科院分区：
文献类型：
--
作者：
V. Rubino;N. Lapusta;A. Rosakis
地壳成熟断层上发生的大型破坏性地震是由于滑动过程中粉碎产生的细颗粒材料（断层泥）层的滑动而发生的。通过在小样本中施加空间均匀滑移的实验，获得了对断层摩擦阻力的一系列见解，断层摩擦阻力是控制地震成核、动态传播和阻止以及由此产生的地震破坏性地面震动的主要因素之一。然而，由于样本大小和足够的成像面临巨大挑战，在实验室中很难研究凿岩摩擦的各种特征如何结合起来确定地震的自发进展。在这里，通过实验室实验，我们表明，自发传播的动态破裂通过复杂的、间歇性的滑动过程和剧烈的摩擦演化，在具有细岩泥的断层区域中导航。这些包括由较低滑移率下的摩擦强化引起的破裂传播的重复停止，以及由与闪速加热一致的较高滑移率下的明显快速摩擦弱化实现的动态地震再成核。细岩泥中摩擦力的自发反复减弱和增强凸显了摩擦力对滑移率和相关过程的根本依赖性，如剪切加热、剪切局部化和离域化、剪切层的膨胀和压实,,, , , , , , , , , , , – 。我们的研究结果扩大了同震减弱可能使地震破裂突破稳定断层区域这一概念的实验支持，对地震灾害具有重大影响。
Large and destructive earthquakes on mature faults in Earth’s crust occur as slip in a layer of a fine granular material—fault gouge—produced by comminution during sliding,. A range of insights into the frictional resistance of faults—one of the main factors controlling earthquake nucleation, dynamic propagation and arrest, and hence the destructive ground shaking of earthquakes,—has been obtained in experiments with spatially uniform slip imposed in small samples,, , , , , , , , , , , , , , , , –. However, how various features of gouge friction combine to determine spontaneous progression of earthquakes is difficult to study in the lab owing to substantial challenges with sample sizes and adequate imaging. Here, using lab experiments, we show that spontaneously propagating dynamic ruptures navigate a fault region with fine rock gouge through complex, intermittent slip processes with dramatic friction evolution. These include repeated arrest of rupture propagation caused by friction strengthening at lower slip rates and dynamic earthquake re-nucleation enabled by pronounced rapid friction weakening at higher slip rates consistent with flash heating,,. The spontaneous repeated weakening and strengthening of friction in fine rock gouge highlights the fundamental dependence of friction on slip rate and associated processes, such as shear heating, localization and delocalization of shear, and dilation and compaction of the shear layer,,, , , , , , , , , , , –. Our findings expand experimental support,of the concept that co-seismic weakening may enable earthquake rupture to break through stable fault regions,, with substantial implications for seismic hazard.