白云母对岩盐断层带摩擦速度依赖性影响的实验研究

doi:10.3969/j.issn.0253-4967.2012.01.007

摘要/Abstract

摘要：

为更好地理解层状硅酸盐对断层强度、滑动速度依赖性及地震活动特征的影响,利用双轴摩擦实验对含白云母岩盐断层带在干燥及含水条件下摩擦的速度依赖性进行了实验研究,并观测了摩擦滑动过程中的声发射,分析了断层带的微观结构。实验结果表明,干燥条件下含白云母岩盐断层带在0.1～100μm/s的速度范围内表现为黏滑和速度弱化,增大σ₂会使断层带从速度弱化向速度强化转化,速度依赖性转换出现在0.1μm/s,其中断层滑动表现为稳滑或应力释放时间较长的黏滑事件;含水条件下含白云母岩盐断层带在0.05～0.01μm/s的速度范围内表现为速度强化,0.1～10μm/s的速度范围内表现为速度弱化,50～100μm/s的速度范围内又转换为速度强化行为。含白云母岩盐断层带在干燥条件下一次黏滑伴随一个或一丛声发射事件,而在含水条件下与稳滑相对应,滑动过程中并未记录到声发射事件。显微结构观察表明,速度弱化域的主要变形机制是岩盐颗粒的脆性破裂和局部化的滑动;干燥条件下,速度强化域的主要变形机制是岩盐颗粒的均匀破裂;含水条件下2个速度强化域对应不同的微观机制,高速域的速度强化受控于岩盐颗粒在白云母相互连结形成的网状结构上的滑动及其均匀碎裂作用,而低速域的速度强化还受岩盐的压溶作用控制。通过与岩盐断层带摩擦实验结果对比可知,白云母的存在对干燥岩盐断层带摩擦滑动方式和速度依赖性没有显著影响,而在含水条件下白云母的存在使得岩盐断层带滑动趋于稳定。实验结果为分析含层状硅酸盐断层的强度和稳定性提供了依据。此外,在速度依赖性转换域上观察到的应力缓慢释放的现象进一步证实了在岩盐断层带摩擦滑动过程中观察到的现象,这对慢地震机制研究具有参考意义。

关键词: 含白云母岩盐断层带, 摩擦实验, 速度依赖性, 微观结构

Abstract:

In order to better understand the effect of phyllosilicate on fault strength, velocity-dependence of friction and seismicity, the velocity-dependence of friction for dry and wet muscovite-bearing halite gouge was studied by using biaxial friction configuration. Acoustic emission produced during the frictional sliding was recorded, and the microstructure of gouge zone was observed. The experiments show that dry gouge behaves stick-slip and velocity weakening at velocities of 0.1～100μm/s; Increasing σ₂ can enhance the transition to velocity strengthening and velocity-dependence transition occurs at velocity of 0.1μm/s, where fault behaves either stable sliding or stick-slip with much longer time than that in the velocity weakening region. Wet gouge behaves velocity strengthening at velocities of 0.05～0.01μm/s, velocity weakening at velocities of 0.1～10μm/s, and velocity strengthening again at velocities of 50～100μm/s. Each stick-slip event corresponds to one or a cluster of AE events for dry gouge, while there is no AE event corresponding to stable sliding for wet gouge. The microscope observation indicates that brittle fracturing and localized slip are predominant in the velocity weakening region and the velocity strengthening is controlled by distributed fracturing of halite under dry condition. While under wet condition, the two velocity strengthening regions correspond to different mechanisms. At higher velocities, the deformation of fault may be controlled by frictional sliding on the network developed by muscovite and uniform fragmentation of halite, and at lower velocities, the deformation of fault is also controlled by pressure solution of halite. Comparing to the results of halite gouge, it can be seen that the existence of muscovite has no effect on sliding mode and velocity-dependence for dry halite gouge, while it enhances the transition to stable sliding for wet halite gouge. The results we got provide basis for analyzing strength and stability of phyllosilicate-bearing faults. The stick-slip with longer time at transitional region confirms what observed in frictional experiments of halite gouge, which is significant for understanding mechanism of slow earthquakes.

Key words: muscovite-bearing halite gouge, frictional experiment, velocity-dependence, microstructure

中图分类号:

P313

缪阿丽, 马胜利. 白云母对岩盐断层带摩擦速度依赖性影响的实验研究[J]. 地震地质, 2012, 34(1): 63-75.

MIAO A-li, MA Sheng-li. EXPERIMENTAL STUDY ON THE INFLUENCE OF MUSCOVITE ON VELOCITY-DEPENDENCE TRANSITION[J]. SEISMOLOGY AND GEOLOGY, 2012, 34(1): 63-75.

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