Fractal dimension of molten surfaces as a possible parameter to infer the slip-weakening distance of faults from natural pseudotachylytes
Fractal dimension of molten surfaces as a possible parameter to infer the slip-weakening distance of faults from natural pseudotachylytes
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DOI：
10.1016/s0191-8141(03)00009-9
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发表时间：
2003-10
影响因子：
3.1
通讯作者：
T. Hirose;T. Shimamoto
中科院分区：
文献类型：
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作者：
T. Hirose;T. Shimamoto
利用旋转剪切高速摩擦仪对辉长岩和二长闪长岩进行的高速摩擦实验表明，沿断层的摩擦熔化和熔层的渐进生长导致滑移减弱，最终达到接近稳定的状态。由于低熔点矿物的选择性熔融和Gibbs-Thomson效应，主岩/熔层界面的熔融面最初非常平坦，但在稳定状态下变得更加复杂和圆形。熔融表面形貌的这种变化可以用分割法测定的分维D来定量表示，从峰值摩擦附近的约1.0到稳态摩擦附近的约1.1。稳态摩擦时的极限分维随着产热率的增加而减小，这可能是由于熔化速度更快、更均匀所致。将D与断层在摩擦熔融过程中的力学行为进行系统的关联，可以通过测量不同位移的滑动面上的天然假玄武岩的D来估计滑动弱化距离和稳态摩擦时的产热率。弱化距离对断层失稳具有重要意义，产热率与断层强度有关。实验研究指出了估计天然断层这些困难数量的方法。
High-velocity friction experiments on gabbro and monzodiorite, using a rotary-shear high-velocity friction apparatus, have revealed that frictional melting and progressive growth of a molten layer along a fault cause slip weakening, eventually reaching a nearly steady-state. The melting surface at the host rock/molten layer interface is initially very flat, but it becomes more complex and rounded in shape towards the steady state owing to the selective melting of minerals with lower melting points and the Gibbs–Thomson effect. This change in the melting-surface topography can be quantitatively expressed by the fractal dimension D, as determined by the divider method, from about 1.0 near the peak friction to around 1.1 near the steady-state friction. The ultimate fractal dimension at steady-state friction tends to decrease with increasing heat production rate presumably due to more rapid and uniform melting. A systematic correlation of D with mechanical behavior of the fault during frictional melting may provide a way of estimating slip-weakening distance and heat production rate at steady-state friction by measuring D for natural pseudotachylytes on slip surfaces with different displacements. The weakening distance is of vital significance in relation to fault instability and the heat production rate is related to the fault strength. The experimental studies point to ways to estimate these difficult quantities for natural faults.