Chen Jianye, van den Ende Martijn P A, Niemeijer André R
HPT Laboratory, Department of Earth Sciences Utrecht University Utrecht the Netherlands.
Faculty of Civil Engineering and Geosciences Technical University of Delft Delft the Netherlands.
J Geophys Res Solid Earth. 2020 Apr;125(4):e2019JB018567. doi: 10.1029/2019JB018567. Epub 2020 Apr 3.
The maximum fault strength and rate of interseismic fault strengthening ("healing") are of great interest to earthquake hazard assessment studies, as they directly relate to event magnitude and recurrence time. Previous laboratory studies have revealed two distinct frictional healing behaviors, referred to as Dieterich-type and non-Dieterich-type healing. These are characterized by, respectively, log-linear and power-law increase in the strength change with time. To date, there is no physical explanation for the frictional behavior of fault gouges that unifies these seemingly inconsistent observations. Using a microphysical friction model previously developed for granular fault gouges, we investigate fault strengthening analytically and numerically under boundary conditions corresponding to laboratory slide-hold-slide tests. We find that both types of healing can be explained by considering the difference in grain contact creep rheology at short and long time scales. Under hydrothermal conditions favorable for pressure solution creep, healing exhibits a power-law evolution with hold time, with an exponent of ~1/3, and an "apparent" cutoff time () of hundreds of seconds. Under room-humidity conditions, where grain contact deformation exhibits only a weak strain-rate dependence, the predicted healing also exhibits a power-law dependence on hold time, but it can be approximated by a log-linear relation with of a few seconds. We derive analytical expressions for frictional healing parameters (i.e., healing rate, cutoff time, and maximum healing), of which the predictions are consistent with numerical implementation of the model. Finally, we apply the microphysical model to small fault patches on a natural carbonate fault and interpret the restrengthening during seismic cycles.
最大断层强度和震间断层强化（“愈合”）速率对于地震危险性评估研究至关重要，因为它们直接关系到地震震级和复发时间。以往的实验室研究揭示了两种不同的摩擦愈合行为，分别称为迪特里希型和非迪特里希型愈合。它们的特征分别是强度变化随时间呈对数线性和幂律增加。迄今为止，对于断层泥的摩擦行为，尚无一种物理解释能够统一这些看似不一致的观测结果。利用先前为粒状断层泥开发的微观物理摩擦模型，我们在对应于实验室滑动-保持-滑动试验的边界条件下，对断层强化进行了分析和数值研究。我们发现，通过考虑短时间和长时间尺度下颗粒接触蠕变流变学的差异，可以解释这两种愈合类型。在有利于压溶蠕变的热液条件下，愈合随保持时间呈现幂律演化，指数约为1/3，“表观”截止时间（）为数百秒。在室湿度条件下，颗粒接触变形仅表现出微弱的应变率依赖性，预测的愈合也随保持时间呈现幂律依赖性，但可以用对数线性关系近似，截止时间为几秒。我们推导了摩擦愈合参数（即愈合速率、截止时间和最大愈合） 的解析表达式，其预测结果与模型的数值实现一致。最后，我们将微观物理模型应用于天然碳酸盐断层上的小断层斑块，并解释了地震周期中的再强化现象。
