Frictional Properties of Sedimentary Rocks and Natural Fault Gouge from the Longmen Shan Fault Zone, Sichuan, China
Frictional Properties of Sedimentary Rocks and Natural Fault Gouge from the Longmen Shan Fault Zone, Sichuan, China
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DOI：
10.1785/0120090287
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发表时间：
2010-05
影响因子：
3
通讯作者：
B. Verberne;Changrong He;C. Spiers
中科院分区：
文献类型：
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作者：
B. Verberne;Changrong He;C. Spiers
在本文中，我们报告了对从 2008 年汶川地震灾区、中国西南部四川省龙门山断裂带 (LFZ) 采集的样本进行的摩擦实验。测试的材料包括由完整的富含粘土的泥岩和砂岩、方解石石灰岩制备的模拟凿凿，以及由切割泥岩和砂岩的沟槽表面破裂形成的天然断层凿凿。富含粘土的样品，包括天然凿岩，主要成分是伊利石和石英。在我们的实验中，我们使用三轴试验机在相当于 LFZ ～2 km 深度的条件下，在锯切驱动块之间剪切了 1 毫米厚的凿孔层。温度从 25°C 变化到 150°C，为了研究摩擦的速度依赖性，我们将剪切位移速率调整为 1.22 至 0.122 μm/s。我们的结果表明，天然泥岩比原岩泥岩和砂岩更富含伊利石，而且强度也弱得多，并且其稳态摩擦系数为 ∼0.4，而后者为 ∼0.6。石灰岩泥的显示值为 0.6–0.7。除石灰石外，所有样品均显示出稳定的、速度增强的滑移。石灰石在 25°C–50°C 时表现出速度增强，但在 100°C–150°C 时表现出准静态振荡，并在 150°C 时表现出速度减弱行为。我们应用我们的研究结果来讨论在汶川地震等事件中研究的沉积岩的作用，并认为该地区富含粘土的沉积物可能对从深处传播的破裂具有阻尼作用，而石灰岩可能会加速传播，产生显着的应力下降。
In this paper, we report friction experiments performed on samples collected from the region hit by the 2008 Wenchuan earthquake in the Longmen Shan fault zone (LFZ) of Sichuan, southwestern China. The materials tested consisted of simulated gouges prepared from intact clay-rich mudstone and sandstone, a calcite limestone, plus a natural fault gouge from a trenched, surface rupture cutting the mudstone and sandstone. The clay-rich samples, including the natural gouge, were dominated by illite and quartz. In our experiments, we sheared 1-mm-thick gouge layers between saw-cut driver blocks, using a triaxial testing machine at conditions corresponding to ∼2 km depth in the LFZ. Temperature was varied from 25°C to 150°C, and to investigate the velocity dependence of friction, we stepped the shear displacement rate between 1.22 and 0.122 μ m/s. Our results show that the natural gouge was more illite-rich and much weaker than the protolith mudstone and sandstone and showed a steady-state friction coefficient of ∼0.4 compared with ∼0.6 for the latter. The limestone gouge displayed values of 0.6–0.7. All samples, except the limestone, showed stable, velocity-strengthening slip. The limestone showed velocity-strengthening at 25°C–50°C, but quasi-static oscillations at 100°C–150°C along with velocity-weakening behavior at 150°C. We apply our results to discuss the role of the sedimentary rocks studied during events such as the Wenchuan earthquake and argue that the clay-rich sediments of the region may have a damping effect upon ruptures propagating from depth, whereas the limestone may accelerate propagation, producing significant stress drops.