热水条件下斜长石和辉石断层泥的摩擦滑动研究

在热水条件下对辉长岩的2种主要组成矿物斜长石和辉石进行了摩擦滑动实验研究。结果表明:1)斜长石在整个实验温度范围内(<607℃)显示速度弱化,而辉石除了在200℃附近表现出微弱的速度强化外,在其他温度范围也都表现为速度弱化;2)斜长石在低温时强度随温度的升高而略有增加,高温时强度则随温度的升高而降低。辉石的摩擦强度随着温度的增加没有系统性的变化,在0.74上下波动;3)在热水条件下辉长岩的摩擦性质并不是这2种主要矿物的叠加,有可能是辉长岩中的次要矿物的存在导致了辉长岩的速度强化;4)本实验所得热水条件下的实验结果与干燥条件下的结果有很大差异,再一次表明水的存在极大地影响了岩石的摩擦稳定性     

龙门山断层带浅钻花岗岩中断层泥的摩擦本构参数

文中针对龙门山断层浅层钻探获取的花岗岩体中的断层泥进行了摩擦滑动实验研究。这种断层泥与其他天然断层泥相比,绿泥石的质量分数很高,约为47%。为研究这种黄绿色断层泥在断层浅部低正应力条件下的摩擦滑动性质,选取的实验条件:围压130MPa,采用围压恒定控制,温度25~150℃,孔隙水压50MPa。通过对比其他天然断层泥的实验结果发现,该断层泥强度较高,稳态摩擦系数在0.47~0.51之间。通过与已有的黏土总质量分数相当但矿物不同的天然断层泥的摩擦系数数据对比,表明不同的非云母层状硅酸盐矿物的摩擦强度排序为:绿泥石伊利石蒙皂石。文中的实验条件对应龙门山地区温度不超过150℃,深度不超过8km的浅层地壳环境,实验结果表明该天然断层泥在整个温度范围内均呈速度强化特征,在摩擦滑动中处于稳定状态。但是断层泥的渗透率很低(10-19m~2),在高速摩擦滑动时可能会发生热压作用。基于此可得出结论:龙门山断裂带的切过已有的深度不超过8km的碎屑原岩的断层可能产生稳定黏滞滑动的阻力,不会自发地震成核,而在后期高速摩擦滑动(0.05m/s)时可能会发生同震弱化,形成一定的灾害叠加。     

热水条件下花岗质糜棱岩的摩擦滑动实验研究

为了探讨大陆地壳断层深部的力学性质,我们选择了采自红河断裂带的糜棱岩作为实验样品,进行热水条件下的高温高压摩擦滑动实验.实验在一个以气体为介质的高温高压三轴实验系统中进行.实验条件是：有效正应力为200 MPa;孔隙水压为30 MPa（在400 ℃到600 ℃之间为超临界水条件）;温度为100 ℃到600 ℃;轴向加载的速率范围从0.04 μm/s到0.2 μm/s再到1 μm/s.实验结果表明：（1）当温度小于300 ℃时,糜棱岩的摩擦强度随着温度的上升而增大;当温度大于300 ℃时,糜棱岩的摩擦强度随着温度的上升而减小.这种趋势和以往花岗岩的摩擦滑动数据基本一致;（2）糜棱岩在200 ℃和400 ℃时表现为速度弱化,其余温度下为速度强化;（3）糜棱岩与已有花岗岩的摩擦滑动数据并不完全一致;（4）花岗质糜棱岩速度弱化向速度强化转变的温度在430 ℃附近,以此我们可以推测：在变形机制为摩擦滑动的深部条件下,地震成核的深度范围可以比以往的估计更深.     

脆塑性转化带Carrara大理岩断层稳定性的实验研究

为探究脆塑性转化带断层的力学性质和滑动稳定性,本文采用干燥的Carrara大理岩预切断层(saw-cut)样品,在气体介质三轴高温岩石力学实验仪上开展了摩擦实验研究,实验温度70～400℃,围压30～100 MPa,位移速率在0.08μm·s^-1, 0.4μm·s^-1, 2μm·s^-1之间切换.实验力学数据揭示,不同围压下Carrara大理岩断层摩擦系数随温度变化规律不同：低围压(30 MPa)下,摩擦系数随温度升高先增大后减小,中高围压(≥70 MPa)下摩擦系数则表现为随温度先减小后增大.断层摩擦滑动行为在100～300℃的范围内表现出由稳定的速度强化转化为不稳定的速度弱化,且在400℃左右重新转变为稳定的速度强化.实验后断层滑动面形貌和微观结构分析表明,稳定滑动断层面为高反射镜面,擦痕清晰;黏滑断层面为有光泽的凹凸不平的表面;最高围压下蠕滑的断层面粗糙无光泽,擦痕不可辨别.本文认为受温度激活的塑性变形过程逐步主导了岩石变形,对断层激活发生不稳定滑动至关重要,而高围压则会抑制断层的不稳定滑动.本研究结果不仅为识别野外...     

水热条件下富层状硅酸盐矿物糜棱岩的摩擦特性实验研究

为探索断层岩石摩擦特性对于断层力学性质的影响,我们采集了龙门山汶茂断裂韧性剪切带中的富含层状硅酸盐矿物的糜棱岩样品进行了水热条件下摩擦滑动实验研究.实验在三轴压机之上完成,实验温度为100~600℃,有效正压力100MPa,孔隙水压分别为30MPa和130MPa.为获得摩擦滑动的稳定性参数(a-b),剪切滑移速率在1.22μm·s-1,0.244μm·s-1和0.0488μm·s-1之间切换.实验发现在200~500℃的温度范围内,摩擦系数随着温度的增加而显著增大(约0.56~0.72).在200~300℃范围内,随温度的升高糜棱岩的摩擦滑动表现出由稳定的速度强化向不稳定速度弱化转变的趋势.在有效正压力不变的情况下,孔隙水压的增大会促进糜棱岩的摩擦滑动在500~600℃温度范围内由不稳定的速度弱化向稳定的速度强化的转变.实验给出的断层在原地深度处的脆性和塑性变形机制的转变,有助于理解断层深部的地震成核机制以及成核的温压条件.     

斜长石在下地壳温度及较低有效压力条件下的摩擦滑动

近年来圣安德烈斯断层在下地壳深度上震颤的发现使其力学性质引起了更多的关注。文中对斜长石断层泥在低正应力条件下的摩擦滑动性质进行了实验。实验条件为有效正应力100MPa,采用围压控制,温度100~600℃,孔隙水压30MPa。通过对比有效正应力为200MPa,其他条件都相同时的实验结果发现,斜长石的摩擦滑动力学行为基本一致,仅在本构参数a值随温度的变化规律上略有差异,但在整个温度范围均呈速度弱化。由此可见,有效正应力的降低对斜长石的摩擦滑动行为影响不大,因而在下地壳可以产生不稳定滑动的结论仍然成立。     

白云母对岩盐断层带摩擦速度依赖性影响的实验研究

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0.1 μm/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,白云母的存在对于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.     

高压流体条件下叶蛇纹石摩擦特性及其对俯冲带慢滑移事件的启示

为了探讨在俯冲带构造加载环境中叶蛇纹石矿物的摩擦力学性质,我们使用叶蛇纹石作为实验样品,开展了高压流体条件下的摩擦滑动实验研究.实验在气体介质的高温高压三轴实验系统中进行,实验中的有效正应力为30 MPa,孔隙流体压力为100 MPa,温度范围为100～500℃.实验过程中为了得到叶蛇纹石摩擦强度系数的速度依赖性,我们将轴向加载速率在1.0μm·s^-1、0.2μm·s^-1和0.04μm·s^-1之间进行切换.实验结果发现在实验温度范围内叶蛇纹石的摩擦强度系数随着温度的升高表现出系统的降低趋势,摩擦系数从100℃的0.81降低到500℃的0.41.在高于300℃的温度条件下,叶蛇纹石的剪切力学曲线表现出显著的位移弱化现象.在300℃的温度条件下,叶蛇纹石在0.2～1.0μm·s^-1的加载速率范围内表现出速度强化的摩擦行为,而在0.04μm·s^-1的加载速率下表现为速度弱化.在100～200℃以及400～500℃的温度条件下皆表现为速度强化.我们的实验研究表明在俯冲带地幔楔附近的高压...     

岩石高速摩擦实验的进展

文中简述了地震动力学国家重点实验室近年来在岩石高速摩擦实验方面的进展。为了深化断层与地震力学研究,实验室建设了一套旋转剪切低速-高速摩擦实验装置,可开展滑动速率介于板块运动速率(cm/a量级)至地震滑动速率(m/s量级)的岩石摩擦实验,其中高速摩擦性能填补了实验室的技术空白。以此为依托,围绕汶川地震断层带力学性质研究,开展了一系列高速摩擦实验。结果表明,龙门山断裂带断层泥的高速摩擦性质具有一致性,其高速滑动下显著的滑动弱化必定在汶川地震中极大地促进了破裂的扩展;断层弱化的主导机制是与摩擦生热相关的过程,包括凹凸体急速加热弱化和热压作用;断层泥在经历高速滑动弱化之后摩擦系数可在5~10s内恢复0.4,断层强度的快速恢复是同震主破裂带余震减少的原因之一。基于对实验装置现状和现有成果的分析,展望了近期实验室岩石高速摩擦的发展方向。     

热水条件下黑云母断层泥的摩擦强度与稳定性

黑云母是自然界常见的层状硅酸盐矿物,其摩擦系数不高且化学稳定性好,对其摩擦性质的关注可能会对弱断层的研究有所帮助.本次工作选取的实验温度条件对应于典型地壳强度模型中脆塑性转化带的范围,为300 ℃和400 ℃.有效正应力为200 MPa,孔隙水压包括10 MPa和30 MPa,在此条件下对黑云母模拟断层泥进行摩擦实验研究.实验得出黑云母的摩擦系数平均在0.36左右.速度依赖性随温度升高速度弱化的程度增强,表现为300 ℃为十分微弱的速度弱化,而在400 ℃出现了黏滑行为,代表了更强的速度弱化.显微结构中同时出现了脆性剪切变形和塑性扭折变形,但决定宏观力学性质的显然是脆性剪切变形.在黑云母存在的情况下,本研究的实验结果有助于理解大陆地壳脆塑性转化带中地震的可能性和弱断层深部的变形机制、宏观力学行为以及地震活动.     

水热作用条件下蛇纹石断层泥的摩擦强度和速度依赖性及其地震地质意义

在恒定的正应力和孔隙压力、不同温度下测量了三种蛇纹石断层泥摩擦强度的速度依赖性。在室温下，纤蛇纹石具有很低的摩擦系数（０．２～０．２５），而利蛇纹石和叶蛇纹石的摩擦系数较高，分别为０．３９和０．４５左右。在２５～２００℃范围内，温度变化对纤蛇纹石和叶蛇纹石强度的影响不明显，而利蛇纹石的摩擦系数随温度升高明显增加。室温下，三种蛇纹石的摩擦在较快的滑动速率下表现为微弱的速度弱化，而在较慢的滑动速度下为明显的速度强化，温度的提高有促使速度弱化向速度强化转变的趋势。研究表明，蛇纹石的存在有利于断层的无震蠕动，但这种影响可能主要限于浅部；尽管纤蛇纹石是最软弱的造岩矿物之一，但仍不足以解释圣安德烈斯断层的软弱性     

Development of shear localization in simulated quartz gouge: Effect of cumulative slip and gouge particle size

Frictional sliding experiments were conducted on two types of simulated quartz gouge (with median particle diameters 5 m and 25 m, respectively) at confining pressures ranging from 50 MPa to 190 MPa in a conventional triaxial configuration. To investigate the operative micromechanical processes, deformation texture developed in the gouge layer was studied in samples which had accumulated different amounts of frictional slip and undergone different stability modes of sliding. The spatial patterning of shear localization was characterized by a quantitative measurement of the shear band density and orientation. Shear localization in the ultrafine quartz gouge initiated very early before the onset of frictional sliding. Various modes of shear localization were evident, but within the gouge zoneR ₁-shears were predominant. The density of shear localization increased with cumulative slip, whereas the angle subtended at the rock-gouge interface decreased. Destabilization of the sliding behavior in the ultrafine quartz gouge corresponded to the extension ofR ₁-shears and formation of boundaryY-shear segments, whereas stabilization with cumulative slip was related to the coalescence ofY-shear segments to form a throughgoing boundary shear. In the coarse quartz gouge, the sliding behavior was relatively stable, probably because shear localization was inhibited by distributed comminution. Two different models were formulated to analyze the stress field within the gouge zone, with fundamentally different predictions on the orientations of the principal stresses. If the rock-gouge interface is assumed to be bonded without any displacement discontinuity, then the maximum principal stress in the gouge zone is predicted to subtend an angle greater than 45° at the interface. If no assumption on displacement or strain continuity is made and if the gouge has yielded as a Coulomb material, then the maximum principal stress in the gouge zone is predicted to subtend an angle less than 45°. If the apparent friction coefficient increases with overall slip (i.e., slip-hardening), then the Riedel shear angle progressively decreases with increasing shear strain within the gouge layer, possibly attaining a zero value which corresponds to a boundaryY-shear. Our quantitative data on shear localization orientation are in reasonable agreement with this second model, which implies the coefficient of internal friction to be about 0.75 for the ultrafine quartz gouge and 0.8 for the coarse gouge. The wide range of orientations for Riedel shear localization observed in natural faults suggests that the orientations of principal stresses vary as much as in an experimental gouge zone.     

岩盐断层带摩擦滑动的速度依赖性转换及其地震学意义

为了深入理解断层带摩擦滑动速度依赖性转换及其机制,利用双轴摩擦实验对干燥及含水条件下岩盐断层带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,干燥岩盐断层带在0.1~100 μm/s的速度范围内表现为速度弱化,增大σ₂会使断层带向速度强化转变;含水条件下岩盐断层带在1~100 μm/s的速度范围内表现为速度弱化,而在0.1~0.01 μm/s的速度范围内表现为速度强化,速度依赖性转换出现在0.1~1 μm/s,其中断层表现为振荡或应力释放时间较长的黏滑事件;岩盐断层带在干燥条件下表现出很强的声发射活动,每个黏滑均对应一丛声发射事件,而在含水条件下一次黏滑只对应一个声发射事件.显微观察表明,局部化的脆性破裂是速度弱化域的主要变形机制,分布式的碎裂流动是干燥岩盐断层带在速度强化域的变形机制,颗粒边界迁移以及压溶作用的塑性变形是含水条件下岩盐断层带在速度强化域的主要变形机制,而脆性破裂和塑性变形共同控制着速度依赖性转换域断层带的变形.水的存在促进岩盐发生塑性变形,进而导致断层带从速度弱化向速度强化转换.上述结果有助于理解断层带上地震活动的特征和慢地震的机制.     

流体对石灰岩断层摩擦滑动影响的实验研究

在气体介质三轴高温岩石力学实验仪器上,采用意大利Scaglia Bianca石灰岩,在温度50～300℃、围压150MPa,含50MPa孔隙压、无孔隙压含饱和水和完全干燥三种条件下,开展摩擦滑动实验.实验力学数据和显微结构表明,完全干燥样品在120℃时出现慢滑移,实验样品中没有出现溶解与沉淀.无孔隙压含饱和水条件下,100℃、120℃、150℃条件下出现典型的慢滑移,实验样品中含有微弱的溶解与沉淀;300℃条件下出现黏滑,实验样品中出现沉淀.在含50MPa孔隙压条件下,50℃时的实验表现为典型的稳滑,实验样品中以溶解为主;在100～150℃时,出现慢滑移,实验样品中以溶解为主,沉淀为辅;在200～300℃时,出现典型黏滑,实验样品中以沉淀为主.实验结果表明,石灰岩断层泥摩擦滑动稳定性随温度变化,受流体中碳酸钙的溶解和沉淀作用控制,因此,流体中矿物质的饱和度这一化学性质对断层带的摩擦强度和摩擦滑动稳定性具有显著影响.     

AN EXPERIMENTAL STUDY ON THE PROCESS OF INTERGRANULAR PRESSURE SOLUTION OF PLAGIOCLASE GOUGE UNDER HIGH TEMPERATURE AND PRESSURE: METHOD AND PRELIMINARY RESULTS

To understand the mechanism of lower-crust earthquake and slow slips, it is necessary to study the frictional properties of mafic rocks and their major rock-forming minerals. Previous studies have performed a series of experimental researches on gabbro, basalt and their major constituents. According to the results of previous experiments, frictional sliding of plagioclase under hydrothermal conditions(100~600℃)shows a property of velocity weakening, and the experimental results show that both the direct rate effect parameter(a)and the healing effect parameter(b)increase with temperature, a typical feature for thermally-activated processes. Velocity weakening means property of a shear band that has a stronger friction healing effect than the direct rate effect in the rate and state friction constitutive framework, and the healing effect(b value)in constitutive relation mainly reflects the increase in contact area with time under hydrothermal conditions, with some minor effect of structural changes. Since the microphysical mechanism of feldspar minerals at the contacts is mainly brittle cataclasis for temperatures below 600℃, the significant frictional healing effect in this case can only be explained by the mechanism of pressure solution. In order to determine if the dissolution process of plagioclase actually occurs on the laboratory time scale, we conducted hydrostatic experiments on plagioclase powder samples under hydrothermal conditions whereby frequent contact switch between particles seen in frictional sliding experiments can be avoided, making the observation on the dissolution sites possible. Experimental temperatures were 400℃ and 500℃, with confining pressure of 90~150MPa, pore pressure of 30MPa, with 2mm initial thickness of fault gouge. The mechanical data show that a creep process occurred in the plagioclase fault gouge in the experimental temperature and pressure range; and the microstructures of the experiment show that precipitation of new grains is prevalent as the product of pressure solution process between plagioclase particles. At the same time, it is observed that the contact points have an appearance similar to fused, fuzzy structure as signatures of dissolution. The results of our experiments provide a definite experimental evidence for the healing mechanism in friction of plagioclase and for the theoretical relation between unstable slip and the pressure solution process. The results of the experiments are summarized as follows: (1)Drainage rate of pore water in plagioclase gouge was high in the first few hours of experiment, but gradually decreases over time for both temperature and pressure series of experiments slowing down to a steady state. This feature indicates that there is a creep process that evolves inside the plagioclase gouge. In the temperature-series experiments, the drainage rate of the pore water in the plagioclase gouge at 400℃ is relatively low than the cases for higher temperatures. Thus, the applied temperature is positively correlated with the creep of plagioclase gouge. (2)Scanning electron microscopy(SEM)observations of the experimentally deformed samples were performed on thin sections cut along the sample axis. Firstly, from the images of microstructure, it was found that the degree of particle fracture became more significant at a higher effective pressure, with smaller pore volume between particles. In the temperature-series experiments it was found that the degree of compaction of plagioclase gouge increased with increasing temperature. Precipitation of plagioclase grains in layered structures was generally observed in high-magnification images, indicating the presence of pressure solution processes. Contact points were also found to be in a state of ambiguity that seems to be a fused morphology, but the details of the structure remain to be determined by further observations. The above results indicate that the pressure solution process of plagioclase particles can occur on a typical laboratory time scale, and the results of this study provide robust experimental evidences for the theory that links between pressure solution and the mechanism of frictional healing and unstable slips for plagioclase.     

安宁河断层地震成核条件研究——来自天然花岗岩断层泥摩擦实验的启示

安宁河断层历史上发生过多次强震,现存的地震空区反映了其断层中部近30年来的断层闭锁和应变积累情况,是潜在的大地震危险区.本研究采用断层带内的新鲜花岗岩断层泥样品,在水热条件下开展了摩擦滑动实验,以研究安宁河断层摩擦特性和地震成核条件.实验有效正应力200MPa,孔隙水压30 MPa,温度25～600℃,剪切滑移速率在1...     

FRICTIONAL SLIDING OF PLAGIOCLASE GOUGE UNDER LOWER-CRUST TEMPERATURE AND RELATIVELY LOW EFFECTIVE NORMAL STRESS

The discovery of tremors on the lower crust portion of the San Andreas Fault has attracted more attention on the mechanical properties of the lower crust in recent years, and some experimental studies have been carried out to understand the mechanical behavior. Previous experiments under effective normal stresses of 200MPa have shown that pyroxene and plagioclase mineral separated from the gabbro and their mixtures all show velocity weakening in the lower-crust temperature range, which results in unstable slip when frictional sliding is the dominant deformation mechanism. This work is to examine whether the velocity-weakening behavior of plagioclase gouge also applies to relatively lower effective normal stress. Our experiments were performed under effective normal stress of about 100MPa, with a constant confining pressure control, with pore pressure of 30MPa and temperature of 100℃ to 600℃. We found that the frictional sliding of plagioclase are basically the same with the previous results obtained under effective normal stress of 200MPa, both of which show velocity weakening over the entire temperature range. The only difference is the out-of-trend drop of constitutive parameter a at 600℃ for the lower effective normal stress of 100MPa. It is thus concluded that reducing the effective normal stress has little effect on the sliding stability of plagioclase, and the previous conclusion made for mechanical behavior of the lower crust that unstable slips are possible therein also applies to the lower effective normal stress of 100MPa.     

蒙脱石的脱水作用对断层摩擦本构行为的影响

利用高温双轴摩擦装置，研究了含蒙脱石的断层带在不同温度下摩擦滑动的速度依赖性，以期了解脱水作用对摩擦行为的影响。结果表明，断层带摩擦强度随温度而升高，而速度依赖性较为复杂，以１．４ｕ／ｓ为界，室温和１００℃时，低滑动速率下表现为微弱的速度弱化，高滑动速率下则表现为速度强化；２００℃时均为速度强化；３００℃时高滑动速率下仍为速度强化，但低滑动速率下转变为速度弱化；４００℃以上，均为明显的速度弱化。摩擦行为的变化与脱水过程及相应的断层物质变形方式的变化密切相关