Tectonic tremor as friction-induced inertial vibration
Tectonic tremor as friction-induced inertial vibration
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作为摩擦引起的惯性振动的构造震颤
DOI：
10.1016/j.epsl.2021.117238
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发表时间：
2021
影响因子：
5.3
通讯作者：
Avouac, Jean-Philippe
中科院分区：
文献类型：
--
作者：
Im, Kyungjae;Avouac, Jean-Philippe
慢滑事件经常伴随着震颤，但震颤是如何产生的仍是个谜。在这项研究中，我们测试了它是惯性振动的可能性。对于单位面积质量为M的单自由度弹簧和滑块系统，受法向有效应力σ‘的速率和状态摩擦控制，在低法向应力(σ’)和高加载速率(V L)时产生惯性振动激励。因此，当加载速率(V L)暂时增加时，可以在低有效正应力(σ‘)区激发震颤，例如在高孔隙压力区，就像在慢滑事件中可能发生的那样。高的加载速率有助于维持振动，但只要法向应力足够小，即使在中等速度扰动下，仍可以激发持续时间较长的衰减颤振。我们使用数值模拟来验证这个假设对于一维断层是成立的。在低滑动速率下，脉动的主频接近无摩擦剪切裂纹的共振基频。滑动速度越高，激励的频率越高。我们给出了与局部低有效正应力的断层块惯性振动辐射的震颤相关的自发慢滑事件的模拟。这一模型为与慢滑事件相关的构造震动提供了可能的解释。
Slow slip events are often accompanied by tremor but how tremor is generated is yet elusive. In this study, we test the possibility that it is an inertial vibration. In the case of a single-degree-of-freedom spring and slider system with mass per unit area M, governed by rate-and-state friction with effective normal stress σ′, excitation of inertial vibrations emerges when normal stress (σ′) is low, and loading rate (V l) is high. Accordingly, tremor can be excited in a low effective normal stress (σ′) zone, for example, in a zone of high pore pressure, when the loading rate (V l) is temporally increased, as can happen during a slow slip event. A high loading rate helps to sustain the vibration, but a long-lasting attenuating tremor can still be excited even with a moderate velocity perturbation as long as the normal stress is sufficiently small. We use numerical simulations to verify that this hypothesis holds for a one-dimensional fault. The dominant frequency of the tremor is close to the fundamental frequency of resonance of the frictionless shear crack at a low sliding rate. Higher frequency modes are excited at higher sliding velocity. We show simulations of spontaneous slow slip events associated with tremor radiated from inertial vibration of a fault patch with locally low effective normal stress. This model provides a possible explanation for tectonic tremor associated with slow slip events.
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