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首页> 外文期刊>Journal of geophysical research. Solid earth: JGR >Stability and localization of rapid shear in fluid-saturated fault gouge: 1. Linearized stability analysis
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Stability and localization of rapid shear in fluid-saturated fault gouge: 1. Linearized stability analysis

机译：流体饱和断层泥中快速剪切的稳定性和局部化：1.线性化稳定性分析

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Field observations of major earthquake fault zones show that shear deformation is often confined to principal slipping zones that may be of order 1–100 μm wide, located within a broader gouge layer of order 10–100 mm wide. This paper examines the possibility that the extreme strain localization observed may be due to the coupling of shear heating, thermal pressurization, and diffusion. In the absence of a stabilizing mechanism shear deformation in a continuum analysis will collapse to an infinitesimally thin zone. Two possible stabilizing mechanisms, studied in this paper, are rate-strengthening friction and dilatancy. For rate-strengthening friction alone, a linear stability analysis shows that uniform shear of a gouge layer is unstable for perturbations exceeding a critical wavelength. Using this critical wavelength we predict a width for the localized zone as a function of the gouge properties. Taking representative parameters for fault gouge at typical centroidal depths of crustal seismogenic zones, we predict localized zones of order 5–40 μm wide, roughly consistent with field and experimental observations. For dilatancy alone, linearized strain rate perturbations with a sufficiently large wavelength will undergo transient exponential growth before decaying back to uniform shear. The total perturbation strain accumulated during this transient strain rate localization is shown to be largely controlled by a single dimensionless parameter E, which is a measure of the dilatancy of the gouge material due to an increase in strain rate.
机译：对主要地震断裂带的野外观察表明，剪切变形通常局限于主要的滑动带，该滑动带的宽度可能在1–100μm左右，位于10–100 mm左右的较宽的凿层内。本文研究了观察到的极端应变局部化可能是由于剪切加热，热加压和扩散耦合的可能性。在没有稳定机制的情况下，连续分析中的剪切变形将崩溃到无限薄的区域。本文研究了两种可能的稳定机制，即强化速率的摩擦力和剪胀性。仅就速率强化摩擦而言，线性稳定性分析表明，对于超过临界波长的扰动，凿层的均匀剪切是不稳定的。使用该临界波长，我们可以预测局部区域的宽度与气刨性能的关系。以典型的地壳震源区质心深度处断层泥的代表性参数为基础，我们预测了宽度为5–40μm的局部区域，大致与现场和实验观察一致。仅对于剪胀，具有足够大的波长的线性应变率摄动将经历短暂的指数增长，然后衰减回均匀的剪切。瞬时应变率局部化过程中累积的总摄动应变显示受单个无量纲参数E的控制，该参数是由于应变率增加而引起的切屑材料膨胀率的量度。

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