Frictional Constitutive Behavior of Natural Fault Gouge Materials: Effects of Mineralogy

定义断层泥的物理和力学性质及其与断层行为的关系仍然是理解地震和断层的基本步骤。摩擦速度依赖被认为是解释稳定滑动（地震）和不稳定粘滑（发震）行为差异的最可能机制。表现出速度增强行为的材料只产生固有的稳定摩擦滑移，而表现出速度减弱的材料则能够承载不稳定的破裂。这项工作将定义一套天然和合成混合矿物沟槽的摩擦特性，作为组成的函数。实验计划将侧重于测试(1)俯冲带材料的自然样品，这些材料在高达~250摄氏度的温度下经历了逐渐的蚀变；(2)一套蒙脱土、伊利石和石英的合成混合物，并建立适当的本构方程来描述它们的行为。这项工作将包括：(1)定量x射线衍射（XRD）来确定天然沟槽的组成，(2)在广泛的实验条件下对每种材料进行一系列剪切实验，以及(3)岩石学和SEM表征实验变形的沟槽的微观结构，并与在样品位置观察到的自然微观结构进行比较。这项工作将为与地震断层有关的真实天然断层泥材料提供高质量的摩擦本构特性测量，并定义这些特性随断层泥成分的变化。这项工作将为更好地理解断层行为及其随深度和沿走向的潜在变异性迈出重要的一步。此外，在实验变形槽中织物发育的详细特征将为实验室测量自然断层的应用提供重要的见解。

Saffer EAR-0229585Defining physical and mechanical properties of fault gouge and their relationship to fault behavior remains a fundamental step toward understanding earthquakes and faulting. Frictional velocity dependence is considered the most likely mechanism to explain differences between stable sliding (aseismic) and unstable stick-slip (seismogenic) behavior. Materials that exhibit velocity-strengthening behavior produce only inherently stable frictional slip, whereas those that exhibit velocity-weakening are capable of hosting unstable rupture. This work will define the frictional properties of a suite of natural and synthetic mixed-mineralogy gouges, as a function of composition. The experimental plan will focus on testing (1) natural samples of subduction zone materials that have undergone progressive alteration at temperatures up to ~250 degrees C, and (2) a suite of synthetic mixtures of montmorillonite, illite, and quartz, and developing the appropriate constitutive equations to describe their behavior. This work will include: (1) quantitative x-ray diffraction (XRD) to determine the composition of natural gouges, (2) a series of shearing experiments for each material, over a wide range of experimental conditions, and (3) petrographic and SEM characterization of microstructures in experimentally deformed gouges and comparison with natural microstructures observed in the sample localities. The work will provide high-quality measurements of frictional constitutive properties for realistic natural fault gouge materials relevant to seismic faulting, and define variations in these properties with gouge composition. This work will constitute an important step toward a better understanding of fault behavior and its potential variability with depth and along-strike. In addition, detailed characterization of fabric development in experimentally deformed gouges will provide important insights into application of laboratory measurements to natural faults.