Constitutive properties of clayey fault gouge from the Hanaore fault zone, southwest Japan
Constitutive properties of clayey fault gouge from the Hanaore fault zone, southwest Japan
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DOI：
10.1029/2008jb005683
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发表时间：
2009-04-22
影响因子：
3.9
通讯作者：
Shimamoto, Toshihiko
中科院分区：
文献类型：
--
作者：
Noda, Hiroyuki;Shimamoto, Toshihiko
在滑动速率范围（0.0154-155.54 μ m s（-1））的速度阶跃测试进行天然断层泥含有蒙皂石，云母，和石英从Hanaore断层，日本西南部的露头收集。野外和微观观察表明，剪切变形局限于几厘米或更薄的黑色粘土断层泥层。该层是由多个阶段形成的，并且由于单个事件而难以确定剪切带的宽度。负载点速度突变的实验数据拟合率和状态相关的摩擦定律，再加上弹簧滑块模型，其刚度被视为一个拟合参数。这种处理被证明是必不可少的，以确定本构参数及其误差。速度阶跃成功地与典型的两个状态变量拟合：较大的B（1）具有较短的d（c1），较小的B（2）具有较长的d（c2）。在滑移率高于1 μ m s（-1）时，在大多数情况下，需要负B（2）来拟合数据。实验中的薄断层泥层（类似于200 μ m）使我们能够模拟大的平均剪切应变，这对于识别与负B（2）和长d（c2）相关的状态变量的演变是重要的。实验后的显微组织观察显示Y平面发育不良。这可能与观察到的力学行为一致：在整个实验中，屈服和位移硬化时初始峰值强度的出现较弱。
Velocity step tests at a range of slip rates (0.0154-155.54 mu m s(-1)) are performed using natural fault gouge containing smectite, mica, and quartz collected from an outcrop of the Hanaore Fault, southwest Japan. Field and microscopic observations reveal that the shear deformation is localized to a few centimeters or thinner layer of black clayey fault gouge. This layer is formed by multiple stages, and determining the width of the shear zone due to a single event is difficult to determine. The experimental data on the abrupt jumps in the load point velocity are fitted by a rate-and state-dependent frictional law, coupled with the spring-slider model, the stiffness of which is treated as a fitting parameter. This treatment is shown to be essential to determine the constitutive parameters and their errors. The velocity steps are successfully fit with typically two state variables: larger b(1) with shorter d(c1) and smaller b(2) with longer d(c2). At slip rates higher than 1 mu m s(-1), negative b(2) is required to fit the data in most of the cases. Thin gouge layers (similar to 200 mu m) in the experiment enables us to simulate large averaged shear strain which is important to recognize the evolution of the state variable associated with negative b(2) and long d(c2). Observation of microscopic structure after experiments shows poor development of Y planes. This may be consistent with the mechanical behavior observed: weak occurrence of initial peak strength at yielding and displacement hardening throughout the experiments.