Velocity-weakening friction induced by laboratory-controlled lithification
Velocity-weakening friction induced by laboratory-controlled lithification
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实验室控制的岩化引起的减速摩擦
DOI：
10.1016/j.epsl.2020.116682
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发表时间：
2021
影响因子：
5.3
通讯作者：
Hüpers
中科院分区：
文献类型：
--
作者：
Hüpers
关于主要板块边界断裂带上地震活动的发生，一个主要的假设是，岩化过程负责将不承载地震成核的松散、松散的沉积物转化为居住在孕震带上的摩擦不稳定岩石。以前的实验室研究比较了相同岩石的完整岩石和粉末状岩石的摩擦特性，通常支持这一假说。然而，系统地量化摩擦行为作为岩化的函数仍然是一个挑战。在这里，我们在实验室模拟岩化过程，将岩盐和页岩粉的混合物与岩盐饱和盐水固化，然后干燥。干燥使岩盐以水泥的形式沉淀下来，形成合成岩石。我们通过：(1)直接测量粘聚力，以及(2)测量与粉末相比，石化样品的孔隙率减少来量化石化。我们观察到，每个岩盐-页岩比例的粉状样品表现出主要的速度强化摩擦，而岩化样品当岩盐至少占样品的30wt%时，表现出速度增强和显著的速度减弱的组合。对个别速率相关摩擦参数的分析表明，速度减弱的发生是由于岩化样品的相对较低的值所致。较大的速度弱化与>；∼1 Mpa的凝聚力和>；∼的孔隙率降低50vol%有关。显微结构图像显示，粉末的剪切面倾向于出现石化样品剪切面上看不到的小裂纹。我们的结果表明，胶结作用和孔隙度损失的岩化作用可以促进滑动失稳，支持了发震滑动的岩化假说。
Regarding the occurrence of seismicity on major plate-boundary fault zones, one leading hypothesis is that the processes of lithification is responsible transforming loose, unconsolidated sediment that does not host earthquake nucleation into the frictionally unstable rocks that inhabit the seismogenic zone. Previous laboratory studies comparing the frictional properties of intact rocks and powdered versions of the same rocks generally support this hypothesis. However, systematically quantifying frictional behavior as a function of lithification remains a challenge. Here, we simulate the lithification process in the laboratory by consolidating mixtures of halite and shale powders with halite-saturated brine, which we then desiccate. The desiccation allows precipitation of halite as cement, creating synthetic rocks. We quantify lithification by: (1) direct measurement of cohesion, and (2) measuring the porosity reduction of lithified samples compared to powders. We observe that powdered samples of each halite-shale proportion exhibit predominantly velocity-strengthening friction, whereas lithified samples exhibit a combination of velocity strengthening and significant velocity weakening when halite constitutes at least 30 wt% of the sample. Analysis of the individual rate-dependent friction parameters shows that the occurrence of velocity weakening is due to relatively low values ofafor lithified samples. Larger velocity weakening is associated with cohesion of >∼1 MPa, and porosity reduction of >∼50 vol%. Microstructural images reveal that the shear surfaces for powders tend to exhibit small cracks not seen on the lithified sample shear surfaces. Our results suggest that lithification via cementation and porosity loss can facilitate slip instability, supporting the lithification hypothesis for seismogenic slip.
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