Pore Fluid Pressure Development in Compacting Fault Gouge in Theory, Experiments, and Nature
Pore Fluid Pressure Development in Compacting Fault Gouge in Theory, Experiments, and Nature
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DOI：
10.1002/2017jb015130
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发表时间：
2018-01-01
影响因子：
3.9
通讯作者：
den Hartog, S. A. M.
中科院分区：
文献类型：
--
作者：
Faulkner, D. R.;Sanchez-Roa, C.;den Hartog, S. A. M.
断裂带的强度强烈地依赖于其中的孔隙流体压力。此外，孔隙流体压力的瞬时变化可能导致从蠕变到不稳定滑动的各种滑动行为，表现为地震或缓慢滑动事件。低渗透断层泥在自然界和实验中的摩擦特性会受到孔隙流体压力的影响，即使在边界排水的情况下，孔隙流体压力也会通过断层泥层内的压实作用而发展。在这里的条件下，显着的孔隙流体压力的发展进行了分析，数值和实验。低渗透断层泥在不同滑动速度下的摩擦实验表明，随着滑动速率的增加，摩擦力逐渐减弱，这表明更快的实验无法排出压实产生的孔隙流体压力。实验用于约束孔隙流体压力建立的数值模拟所需的渗透率和孔隙体积的演变。计算结果与实验结果吻合较好，表明计算中考虑了主要的物理过程。该模型被用来分析孔隙流体压力瞬变的摩擦性能的测定的影响，说明，本征速度加强行为可以出现速度减弱，如果孔隙流体压力没有足够的时间来平衡。结果表明，在实验测量低渗透断层泥的摩擦特性时，必须特别注意。考虑了地震作用引起的孔隙流体增压对天然断层弱化的贡献。在大断层连续地震期间，断层泥中孔隙流体的循环增压可能会重置孔隙度，从而削弱压实能力。
The strength of fault zones is strongly dependent on pore fluid pressures within them. Moreover, transient changes in pore fluid pressure can lead to a variety of slip behavior from creep to unstable slip manifested as earthquakes or slow slip events. The frictional properties of low-permeability fault gouge in nature and experiment can be affected by pore fluid pressure development through compaction within the gouge layer, even when the boundaries are drained. Here the conditions under which significant pore fluid pressures develop are analyzed analytically, numerically, and experimentally. Friction experiments on low-permeability fault gouge at different sliding velocities show progressive weakening as slip rate is increased, indicating that faster experiments are incapable of draining the pore fluid pressure produced by compaction. Experiments are used to constrain the evolution of the permeability and pore volume needed for numerical modeling of pore fluid pressure build up. The numerical results are in good agreement with the experiments, indicating that the principal physical processes have been considered. The model is used to analyze the effect of pore fluid pressure transients on the determination of the frictional properties, illustrating that intrinsic velocity-strengthening behavior can appear velocity weakening if pore fluid pressure is not given sufficient time to equilibrate. The results illustrate that care must be taken when measuring experimentally the frictional characteristics of low-permeability fault gouge. The contribution of compaction-induced pore fluid pressurization leading to weakening of natural faults is considered. Cyclic pressurization of pore fluid within fault gouge during successive earthquakes on larger faults may reset porosity and hence the capacity for compaction weakening.