Strain rate effect on fault slip and rupture evolution: Insight from meter-scale rock friction experiments
Strain rate effect on fault slip and rupture evolution: Insight from meter-scale rock friction experiments
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DOI：
10.1016/j.tecto.2017.11.039
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发表时间：
2017-12
期刊：
影响因子：
2.9
通讯作者：
Shiqing Xu;E. Fukuyama;F. Yamashita;K. Mizoguchi;S. Takizawa;H. Kawakata
中科院分区：
文献类型：
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作者：
Shiqing Xu;E. Fukuyama;F. Yamashita;K. Mizoguchi;S. Takizawa;H. Kawakata
通过米尺度岩石摩擦试验，研究应变率对断层滑动和破裂演化的影响。两个由印度元长岩制成的岩石样本，名义接触尺寸为1.5 m长，0.1 m宽，并置并加载在直接剪切配置中，以模拟断层运动。在恒定加载速率为0.01 mm/s ~ 1mm /s，固定法向应力为6.7 MPa的条件下进行了一系列试验，模拟了应变速率变化的条件。测压元件和位移传感器用于检测宏观故障行为，而靠近故障的高密度应变片阵列用于检测局部故障行为。结果表明：随着加载速率的增加，宏观峰值强度、强度下降率和强度下降率均有所增加；在局部尺度上，观察结果表明，缓慢的加载速率有利于特征破裂的产生，这些破裂总是在大约相同的位置以慢滑动的形式成核。相反，快速加载速率会促进破裂成核非常突然和震源位置沿走向的分散。在一定的传播距离下，随着加载速率的增加，破裂速度有增大的趋势。我们提出应变率相关的断层破碎过程可以提高粘滞期断层愈合的效率，并与愈合时间一起控制断层强度的恢复。此外，滑移期激活了一个依赖于应变率的弱化机制，该机制与应变能一起选择了断层滑移和破裂扩展的模式。研究结果有助于了解自然界断层滑动和岩石变形模式的谱，并强调非均质性在调整不同应变速率下断层行为中的作用。
We conduct meter-scale rock friction experiments to study strain rate effect on fault slip and rupture evolution. Two rock samples made of Indian metagabbro, with a nominal contact dimension of 1.5 m long and 0.1 m wide, are juxtaposed and loaded in a direct shear configuration to simulate the fault motion. A series of experimental tests, under constant loading rates ranging from 0.01 mm/s to 1 mm/s and under a fixed normal stress of 6.7 MPa, are performed to simulate conditions with changing strain rates. Load cells and displacement transducers are utilized to examine the macroscopic fault behavior, while high-density arrays of strain gauges close to the fault are used to investigate the local fault behavior. The observations show that the macroscopic peak strength, strength drop, and the rate of strength drop can increase with increasing loading rate. At the local scale, the observations reveal that slow loading rates favor generation of characteristic ruptures that always nucleate in the form of slow slip at about the same location. In contrast, fast loading rates can promote very abrupt rupture nucleation and along-strike scatter of hypocenter locations. At a given propagation distance, rupture speed tends to increase with increasing loading rate. We propose that a strain-rate-dependent fault fragmentation process can enhance the efficiency of fault healing during the stick period, which together with healing time controls the recovery of fault strength. In addition, a strain-rate-dependent weakening mechanism can be activated during the slip period, which together with strain energy selects the modes of fault slip and rupture propagation. The results help to understand the spectrum of fault slip and rock deformation modes in nature, and emphasize the role of heterogeneity in tuning fault behavior under different strain rates.