Frictional properties and 3-D stress analysis of the southern Alpine Fault, New Zealand
Frictional properties and 3-D stress analysis of the southern Alpine Fault, New Zealand
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DOI：
10.1016/j.jsg.2018.06.003
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发表时间：
2018-09
影响因子：
3.1
通讯作者：
C. Boulton;C. Boulton;N. Barth;D. Moore;D. Lockner;John Townend;D. Faulkner
中科院分区：
文献类型：
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作者：
C. Boulton;C. Boulton;N. Barth;D. Moore;D. Lockner;John Townend;D. Faulkner
新西兰阿尔卑斯断裂带（AF）在大震级地震中准周期性破裂。古地震学证据表明，在所有已知的AF地震中，约有一半终止于该断层的中部和西南威斯特兰段之间的边界。在那里，断层形态和隆升极性发生了变化。South Westland AF在052°/82°SE方向的构造上表现为斜正断层运动，沿走向至少35 km，包含富含皂石的主滑带沟槽。新的热液摩擦实验表明，皂石断层泥在温度（T= ~ 210 ℃）和有效法向应力（σn′ = 31.2 ~ 93.6 MPa）范围内的摩擦系数为μ= 0.12 ~ μ= 0.16。在0.01 ~ 3.0 μm/s范围内，皂土泥在所有速度阶上均呈速率强化，有利于地震蠕变。三维应力分析表明，南韦斯特兰断裂带在摩擦性弱皂石断层泥内具有良好的区域应力场导向。在几何上，在任何摩擦系数超过μ ~ 0.5的断层形成材料中，断层都存在严重的错位。易发生地震蠕变的弱沟槽、强陡岩和低分解剪应力的组合可能阻碍了南韦斯特兰阿尔卑斯断裂带地震破裂的传播。
New Zealand's Alpine Fault (AF) ruptures quasi-periodically in large-magnitude earthquakes. Paleoseismological evidence suggests that about half of all recognized AF earthquakes terminated at the boundary between the Central and South Westland sections of the fault. There, fault geometry and the polarity of uplift change. The South Westland AF exhibits oblique-normal fault motion on a structure oriented 052°/82°SE that, for at least 35 km along strike, contains saponite-rich principal slip zone gouges. New hydrothermal friction experiments reveal that the saponite fault gouge is frictionally weak, exhibiting friction coefficients betweenμ= 0.12 andμ= 0.16 for a range of temperatures (T= 25–210 °C) and effective normal stresses (σn' = 31.2–93.6 MPa). The saponite gouge is rate-strengthening in all velocity steps performed at velocities between 0.01 and 3.0 μm/s, behavior conducive to aseismic creep. A three-dimensional stress analysis shows that the South Westland AF is favorably oriented with respect to the regional stress field for slip within the frictionally weak saponite fault gouge. Geometrically, the fault is severely misoriented for slip in any fault-forming materials with friction coefficients exceedingμ∼0.5. The combination of weak gouges prone to aseismic creep, strong asperities, and low resolved shear stress may impede earthquake rupture propagation along the South Westland Alpine Fault.