Friction velocity dependence of clay-rich fault material along a megasplay fault in the Nankai subduction zone at intermediate to high velocities
Friction velocity dependence of clay-rich fault material along a megasplay fault in the Nankai subduction zone at intermediate to high velocities
复制标题
南开俯冲带巨型张断层富粘土断层物质中高速摩擦速度依赖性
DOI：
10.1029/2011gl049314
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发表时间：
2011
影响因子：
5.2
通讯作者：
A
中科院分区：
文献类型：
--
作者：
Tsutsumi;A.;Fabbri;O.;Karpoff;A. M.;Ujiie;K. and Tsujimoto;A
在含水饱和滑动速度为0.0026~260 mm/S、位移为250 mm的条件下，在正应力为5 Mpa的条件下，考察了南开增生杂岩内一条巨型断裂中采集的富粘土断层材料的摩擦特性。我们的结果表明，断层物质可以表现出两个阶段的速度弱化行为：低速(v<；2.6 mm/S)的弱化，表现为较小的摩擦速度依赖性(a−b的绝对值典型地为<；0.005)和高速(v>；26 mm/S)的急剧弱化。这种断层弱化的过程可能会对沿巨型断层的断层模式提供重要的约束。在滑动速度为0.026~2.6 mm/S的范围内，既存在速度弱化的断层物质，也存在速度增强的断层物质。对于慢滑移速度(v=0.26 mm/S)，速度增强试件的摩擦因数μ相对较小(μ=0.28~0.35)，而速度减弱试件的摩擦因数μ较低(μ=0.38~0.49)。显微结构分析表明，速度增强型样品表现出均匀的变形织构，整个断层泥都发生了变形，而速度减速型材料则表现出剪切局部化的证据，变形集中在狭窄的副剪切上。
The frictional properties of clay‐rich fault material collected from a megasplay fault within the Nankai accretionary complex were examined in frictional experiments performed at a normal stress of 5 MPa under water‐saturated conditions for slip velocities from 0.0026 to 260 mm/s with >250 mm of displacement. Our results reveal that the fault material can show two stages of velocity weakening behavior: weakening at slow velocities (v< 2.6 mm/s), characterized by a small degree of friction velocity dependence (the absolute value of (a−b) is typically <0.005), and a dramatic weakening at high velocities (v> 26 mm/s). Such a process of fault weakening may provide important constraints on models of faulting along a megasplay fault. At slip velocities from 0.026 to 2.6 mm/s, there exist both velocity‐weakening and velocity‐strengthening fault materials. The frictional coefficient values,μ, for slow slip velocities (v= 0.26 mm/s) are relatively low (μ= 0.28–0.35) for velocity‐strengthening samples compared with velocity‐weakening samples (μ= 0.38–0.49). Microstructural analyses reveal that velocity‐strengthening samples show homogeneous deformation textures in which the entire gouge layer is deformed, whereas velocity‐weakening materials show evidence of shear localization in which deformation is concentrated along narrow subsidiary shears.