Comminution and fluidization of granular fault materials: implications for fault slip behavior
Comminution and fluidization of granular fault materials: implications for fault slip behavior
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DOI：
10.1016/s0040-1951(03)00133-1
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发表时间：
2003-05-29
期刊：
影响因子：
2.9
通讯作者：
Otsuki, K
中科院分区：
文献类型：
--
作者：
Monzawa, N;Otsuki, K
虽然地壳浅层的断层不可避免地与岩石的粉碎有关，但粉碎颗粒物质本身的力学性质会影响断层的滑动行为。因此，任何断层的力学行为都是沿着一条演化路径发展的。断层岩的粉碎开始于接近1.5的分维（二维测量），在该分维处，给定的颗粒由可达到的最大数量的颗粒支持，因此是最强的。随着粉碎的进行，分形维数增加，因此粉碎本身是一种滑动弱化机制。在适当的条件下，粉碎的粒状材料在地震滑动事件中可能会流化。在本文中，我们开发了一种新的方法来识别粒状断层岩石，经历了流化，其中检测概率的碎片对应物是一个关键参数。将该方法应用于四个断层岩样，取得了成功的结果。粉末技术的知识告诉我们，由可达到的最大体积分数归一化的颗粒的体积分数是粒状材料的动态特性的最重要的参数，并且一旦粒状断层材料被流化，断层平面变得几乎无摩擦。从I的颗粒的归一化体积分数的一个小的减少是从由颗粒摩擦和接触应力破碎的变形机制的相变流化的必要条件。只有在无约束条件下进行剪切时，才能实现这一条件，这就要求差距。断层墙之间的距离变宽。Brune等人[Tectonophysics 218（1993）59]提出的正常界面振动似乎是最合适的原因，我们提出了两条现场证据，支持这种机制在自然界中起作用。(C)2003 Elsevier Science B.V保留所有权利。
Whilst faulting in the shallow crust is inevitably associated with comminution of rocks, the mechanical properties of the comminuted granular materials themselves affect the slip behavior of faults. Therefore, the mechanical behavior of any fault progresses along an evolutionary path. We analyzed granular fault rocks from four faults, and deduced an evolutionary trend of fractal size frequency. Comminution of fault rocks starts at a fractal dimension close to 1.5 (2-D measurement), at which a given grain is supported by the maximum number of grains attainable and hence is at its strongest. As comminution proceeds, the fractal dimension increases, and hence comminution itself is a slip weakening mechanism. Under the appropriate conditions, comminuted granular materials may be fluidized during seismic slip events. In this paper, we develop a new method to identify the granular fault rocks that have experienced fluidization, where the detection probability of fragmented counterparts is a key parameter. This method was applied to four fault rock samples and a successful result was obtained. Knowledge from powder technology teaches us that the volume fraction of grains normalized by maximum volume fraction attainable is the most important parameter for dynamic properties of granular materials, and once granular fault materials are fluidized, the fault plane becomes nearly frictionless. A small decrease in the normalized volume fraction of grains from I is a necessary condition for the phase transition to fluidization from the deformation mechanism governed by grain friction and crushing by contact stresses. This condition can be realized only when shearing proceeds under unconstrained conditions, and this demands that the gap. between fault walls is widened. Normal interface vibration proposed by Brune et al. [Tectonophysics 218 (1993) 59] appears to be the most appropriate cause of this, and we presented two lines of field evidence that support this mechanism to work in nature. (C) 2003 Elsevier Science B.V All rights reserved.