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着重研究拉张或挤压型雁列式断层标本变形过程中声发射(简称AE，下同)的时空演化特征. 结果表明，预置构造对AE空间分布格局具有较强的控制作用，随着差应力的增加，AE首先在两个端点附近丛集，之后向两端点连线附近集中，出现明显的破裂局部化现象，较大事件还通常集中于某一端点附近反复发生. 前期微破裂丛集图象指示后期宏观破裂的扩展方向及扩展范围. 拉张和挤压型雁列区宏观破裂方向分别与轴向应力方向垂直和平行. 雁列式断层标本变形过程中，破裂前的弱化阶段相对较长、弱化过程明显. 微破裂事件累积频次指数增长可能是系统失稳前的典型征兆之一，而雁列区宏观破裂之后，AE数量逐渐减少、应变释放相对减弱. 摩擦滑动过程中，大的粘滑失稳前未见有AE活动前兆性的增强过程.雁列区的b值变化在失稳前显示趋势性降低——快速回升这一典型的变化过程，b值降低一般发生在差应力增强过程之中，并有可能延续至弱化阶段，而快速回升则一般发生在破裂失稳前的短时期内. 对比研究表明，构造差异所导致的b值差异远大于b值随差应力的增加而产生的变化量，而对同一构造标本，力学状态的改变会导致AE序列时序特征的急剧变化，较高的加载速率对应较高的应变能释放及明显的低b值. 先期破碎带由于较低的破坏强度，其对差应力的微小变化具有特殊敏感性，从而成为源、兆分离、窗口或敏感点效应等地震活动性前兆现象的一种可能的原因. 相似文献
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ShengLi Mi ShunYun Chen PeiXun Liu XiaoYan Hu KaiYing Wang YuanMin Huang 《中国科学D辑(英文版)》2008,51(10):1436-1445
Studying the effect of geometrically irregular bodies on the mechanical behavior of fault activity is of significance in understanding the seismic activity along a fault zone. By using rock mechanics ex- periment with medium-scale samples, we have studied the effect of fault jogs, the most common irregularity along fault zones, on frictional behavior. The research indicates that extensional fault jog can be easily fractured because of its low strength and the fractured jog has no obvious resistance to fault sliding, and the micro-fractures occurring in the jog are indicative of stick-slip along the faults. The fault zone containing extensional jogs is characterized by velocity weakening and can be described by rate and state friction law. Compressional fault jog makes fault sliding more difficult because of its high fracturing strength, but the micro-fractures occurring in the tensile areas around fault ends at higher stress level can provide necessary condition for occurrence of stick-slip along the faults before the jog is fractured and thus act as precursors of fault instability. Compression jog can be taken as a stable indicator of fault segmentation until the jog is completely fractured and two faults are linked. 相似文献
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雁列式断层变形过程中物理场演化的实验研究（二） 总被引：6，自引：1，他引：6
在双轴压缩条件下对由挤压型和拉张型雁列式断层组合而成的复杂雁列断层系变形过程中声发射、断层位移及应变的时空演化进行了实验研究，结果表明，复杂雁列式断层系的变形过程及相应的物理场演化并非是两种雁列式断层的简单叠加，而是包含着它们之间的相互作用。能量较强的声发射事件成核部位主要集中在应力水平较低的张性雁列区附近的主于断层上，而不是应力水平较高的压性雁列区，但这种事件发生的时间则明显受控于压性雁列区的变形过程 相似文献
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雁列式断层变形过程中物理场演化的实验研究（一） 总被引：21，自引：3，他引：21
在双轴压缩条件下对挤压型和拉张型雁列式断层变形破坏过程中声发射、断层位移及应变场的时空演化进行了实验研究。研究表明，两类雁列式断层具有类似的变形破坏过程，即前期以雁列区的破裂贯通为主，后期以沿断层的滑动为主。但挤压型雁列区内可积累较高的应变能，有较强的应变释放和声发射活动，雁列区对滑动始终起着阻碍作用；而拉张型雁列区内难以产生快速的应变释放和较强的声发射活动，雁列区对后期的滑动也无明显的阻碍作用。两类雁列区贯通所引起的失稳均有明显的前兆，而在随后滑动过程中失稳前兆的出现，取决于断层不同部位或段落之间是否有应变传递 相似文献
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在实验室使用红外热像仪和接触式测温仪同步观测记录了压性和张性雁列断层失稳错动前后的热场变化过程.从实验记录中发现，在断层失稳引起温度场和热红外辐射亮温温度场上升之前，在两断层段之间的岩桥区发生降温变化.断层带开始升温发生在失稳前2～3 s内，岩桥区的降温却发生在失稳前约20s，这两个超前时间长度相差近一个量级.此类热场先降后升变化过程在雁列构造变形中有一定的普遍性，可能作为雁列断层失稳错动的热场前兆模式.根据实验观测结果，详细描述了上述热场变化的时间过程及其空间分布特征，分析了产生此种失稳前兆模式的机制，显著异常出现的条件及有利观测部位，讨论了它在地震前兆探索等研究中的意义. 相似文献
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对几种不同结构的岩石标本在变形过程中声发射b值和频谱随时间的变化特征进行了对比研究 ,其中包括完整花岗岩标本、含有天然愈合节理的花岗岩标本、含有拉张型和挤压型雁列式断层以及平直断层的标本等。研究表明 ,声发射b值和频谱的特征不仅会受标本结构的影响 ,而且在同一标本的不同变形阶段也可能表现出不同的特征 ,其机制与变形方式以破裂为主或以摩擦为主有关。当变形以破裂为主时 ,声发射b值和频谱在失稳前会出现明显的下降 ;当变形以摩擦为主时 ,声发射b值和频谱在失稳前变化相对较小 ,且上升或下降均可能出现。实验结果意味着b值和频谱特征作为失稳前兆 ,在不同的构造环境下可能会有不同的特征 ,而强震孕震区内不同断裂构造的存在会造成前兆时空分布的非均匀性 相似文献
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寻找地震前兆是国内外地震预报的难点.在实验室开展岩石变形实验,观测相关物理量的演化特征和规律,是前兆探索中重要的基础工作.本文对压性雁列断层进行变形实验,根据应力时间曲线将具有前兆意义的变形阶段分为强偏离线性阶段、亚失稳阶段和失稳阶段,利用红外热像仪记录各个阶段的热场变化,特别是亚失稳阶段的热场表现.研究结果显示:强偏离线性阶段,岩桥区挤压升温;亚失稳阶段,断层带增温,且高温点扩展连通,断层带内侧卸载降温,断层带上的协同化增温和断层带内侧(包含岩桥区)的协同化降温是失稳前的重要信号;失稳阶段,应力释放,标本整体降温,只有断层带因摩擦升温.总之,亚失稳阶段的热场具有明显特征,利于识别出亚失稳态;不同变形阶段、不同构造部位温度变化不同,在寻找与构造活动相关的热异常时,应考虑变形所处的阶段及异常所处的构造部位. 相似文献
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The spatial and temporal distributions of acoustic emission （AE） during the deformation of samples containing an inhomogeneous fault have been studied under biaxial compression. The results show that the fault strength and the duration from loading to failure increase and the failure mode changes from abrupt instability to gradual failure with increase of lateral stress σ2. The pre-setting fault and its heterogeneity play an important role in controlling AE spatial distribution during the deformation. The basic pattern of AE spatial distribution is controlled by the pre-setting fault, especially the parts with inhomogeneous strength and the strong segment, and the localization of fracturing starts from the positions with inhomogeneous strength, With increase of σ5, the dense AE distribution area spreads from the positions with inhomogeneous strength to the whole strong segment gradually. AE temporal sequence is significantly affected by σ2. The fault shows abrupt instability in final failure, which occurs on a background of ＂enhancement-quiescence＂ in microfracturing activity at lower σ2. At higher σ5, the fault shows gradual failure, and AE occurrence rate increases continuously and AER increase exponentially before and after the failure, The effect of σ2 on b-value is also remarkable, b-value shows precursory decrease in the weakening stage when fault behavior is abrupt instability, but it shows balanced change when fault behavior is gradual failure, 相似文献
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EXPERIMENT STUDY ON ACOUSTIC EMISSION,MICROSEISM AND CHARGE INDUCTION DURING FRACTURE PROCESS OF GRANITE WITH FAULT ZONE UNDER UNIAXIAL COMPRESSION 
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下载免费PDF全文 As the rock samples will produce abnormal signals of acoustic emission, microseismic and charge signals under external loading, the waveform comprehensive monitoring devices are used to synchronously monitor acoustic emission, microseismic and charge signals during the deformation and failure process of granite with fault zone under uniaxial compression. The results show that, the granite with fault zone has obvious synchronous precursory signals of acoustic emission, microseism and charge induction in the elastic deformation stage, and has high amplitude synchronous precursory signals in the instability destruction stage. The influence of fault zone on granite samples strength is remarkable, and the uniaxial compressive strength of samples with the fault zone is greatly reduced. With the angle of the fault zone decreasing, the uniaxial compressive strength of the specimens is reduced, the samples are more liable to instability and the energy of instability destruction is greater. With the fault zone angle of granite samples decreasing, the acoustic emission, microseismic and charge induction signals increase in the deformation and failure process of samples. The samples stress decreases when the acoustic emission, microseismic and charge induction precursory signals appear synchronously. The duration of acoustic emission, microseismic and charge induction precursory signals is increasing in the instability destruction stage. When the angle of the fault zone reaches 30°, the mutability of acoustic emission, microseismic and charge induction signal increases, the time to enter the dangerous stage is much earlier, and the acoustic emission events of large magnitude increase significantly, and the large angle faults of coal mine are more dangerous. The intensive and high amplitude synchronous precursory signals of acoustic emission, microseism and charge induction are produced before the instability destruction, and the signals duration is shorter. The intensive and strongest synchronous precursory signals of acoustic emission, microseism and charge induction are produced in the instability destruction, and the signals duration is longer. Acoustic emission monitoring data can better reflect the micro rupture of rock. And combined with the acoustic emission, microseismic and charge induction precursory signals, the precursory information of rock instability destruction can be obtained more accurately. 相似文献
12.
Mireille Laigle Anne Becel Batrice de Voogd Alfred Hirn Tuncay Taymaz Serdar Ozalaybey Members of SEISMARMARA Leg Team 《Earth and Planetary Science Letters》2008,270(3-4):168-179
Increased source strength, streamer length and dense spatial coverage of seismic reflection profiles of the SEISMARMARA Leg 1 allow to image the deep structure of the marine North Marmara Trough (NMT) on the strike-slip North Anatolian Fault (NAF) west of the destructive Izmit 1999 earthquake. A reflective lower crust and the Moho boundary are detected. They appear upwarped on an E-W profile from the southern Central Basin eastwards, towards more internal parts of the deformed region. Thinning of the upper crust could use a detachment suggested from an imaged dipping intracrustal reflector that would allow upper crustal material to be dragged from beneath it and above the lower crust, accounting for the extensional component but also southwest motion of the southern margin of the NMT. Sections across the eastern half of the NMT, crossing the Cinarcik and Imrali basins, reveal several faults that are active reaching into the basement and have varying strike and proportions of normal and strike-slip displacement. They might be viewed as petals of a large scale negative flower-structure that spreads over a width of 30 km at surface and is rooted deeper in the lithosphere. Under the Central Basin a very thick sediment infill is revealed and its extensional bounding faults are active and imaged as much as 8 km apart down to 6 km depth. We interpret them as two deep-rooted faults encompassing a foundering basement block, rather than being merely pulled-apart from a jog in a strike-slip above a décollement. The deep-basin lengthening would account for only a modest part of the proposed 60 km finite motion since 4 Myr along the same direction oblique to the NMT that sidesteps the shear motion from its two ends. Thus differential motion occurred much beyond the deep basins, like subsidence involving the NMT bounding faults and the intracrustal detachments. The complex partitioned motion localized on active faults with diverse natures and orientations is suggested to represent the overburden deformation induced from horizontal plane simple shear occurring in depth at lithospheric scale, and in front of the North Anatolian Fault when it propagated through the region. 相似文献
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通过物理模拟证明交叉断层上会交替地发生失稳事件。两条交叉的断层在活动中既相互促进 ,又相互制约 ,即一条断层既可能使另一条断层发生闭锁而积累应变 ,又可能触发其错动。每条断层的位移速率、总位移量以及失稳事件数与断层方向和主压应力轴的夹角有关。各断层段的位移有时体现为断层围限块体的平移运动 ,而有时则体现为块体的旋转运动。发生在不同部位的失稳事件影响范围不同 ,在正应力较大的断层上失稳事件影响范围大。涉及交叉断层的较大失稳事件发生前常出现前兆性小事件。交叉断层的交替活动实际上由变形场中块体的运动所控制 相似文献
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PRELIMINARY APPLICATION OF FOCAL MECHANISM SOLUTIONS OF SMALL AND MEDIUM-SIZE EARTHQUAKES TO FAULT STABILITY ANALYSIS IN THE SOUTHEASTERN TIBETAN PLATEAU 下载免费PDF全文
下载免费PDF全文 Analysis of stress state of faults is helpful to understand crustal mechanical properties and seismicity. In the paper, we invert the horizontal crustal stress field in the southeastern Tibetan plateau using focal mechanism solutions of small and medium-size earthquakes, and apply them to estimate the stability of regional major faults.
Firstly, we collect focal mechanism solutions of small and medium-sized earthquakes in the southeastern Tibetan plateau. The dataset includes more than 1 000 focal mechanism solutions in the past twenty years. Magnitudes of these earthquakes vary from M3.0 to M6.0. Most of the focal mechanism solutions were determined using waveform inversion technique. Although most of focal mechanism solutions in the southeastern Tibetan plateau are strike-slip faulting, their spatial pattern is different in sub-regions. Normal faulting earthquakes mainly occurred in the western Sichuan region, reverse faulting earthquakes mainly occurred in the boundary zone between the Tibetan plateau and the South China craton, and strike-slip faulting earthquakes mainly occurred in the central and southern Yunnan region.
Next, we settle on a mesh with grid spacing of 0.5° in longitude and latitude in the region and invert the horizontal crustal stress field at each grid point. Spatial variation of the maximum principal stress axis in the southeastern Tibetan plateau shows a clockwise rotation around the eastern Himalaya syntax. The azimuth of maximum compressional stress axis is about 88.1° in the western Sichuan region, about 124.6° in the South China craton, and about 21.6° in the western and southern Yunnan region. The azimuth of regional maximum compressional stress is nearly parallel to the direction of terrain elevation gradient, and that of the minimum compressional stress is nearly parallel to the tangential direction of the topographic elevation contours. The spatial pattern reflects the control role of gravity spreading of the Tibetan plateau on the regional horizontal stress field.
Finally, we analyzed regional fault stability based on these collected focal mechanism solutions. The fault instability parameter (I) is defined based on the Mohr-Coulomb criterion and indicates the degree of fault approximating to rupture. The instability parameters on fourteen major faults in the southeastern Tibetan plateau were calculated. Our results show that the stability of the Lianfeng-Zhaotong Fault is the lowest before 2014 in the region, which indicates the fault zone is close to rupture at that time. Our results provide a new useful tool to assess regional seismic potential using dense focal mechanism solutions. 相似文献
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Hydraulic fracturing reservoir reconstruction technology is crucial in the development of shale gas exploitation techniques.Large quantities of high-pressure fluids injected into shale reservoirs significantly alter compressional(P)and shear(S)wave velocities,rock mechanical parameters,and anisotropic characteristics.In this study,differentiated hydraulic fracturing petrophysical experiments were carried out on Longmaxi Formation shale under pseudo-triaxial stress loading conditions.The effects of stress loading methods,and water-rock physical and chemical reactions on P-and S-wave velocities and rock mechanical parameters were compared.The experimental results showed that isotropic stress loading may increase the P-and Swave velocities and Young’s modulus of dry shale kldnsample.Furthermore,it may lead to a weakening of the corresponding anisotropy.In contrast,differential stress loading was able to improve the anisotropy of Young’s modulus and accelerate the decrease in the compressive strength of shale in the vertical bedding direction.The water-rock physical and chemical reactions prompted by hydraulic fracturing was found to"soften"shale samples and reduce Young’s modulus.The influence of this"soften"effect on the compressional and shear wave velocities of shale was negligible,whilst there was a significant decrease in the anisotropy characteristics of Thomsen parameters,Young’s modulus,and Poisson’s ratio.The negative linear relationship between the Poisson’s ratios of the shale samples was also observed to lose sensitivity to stress loading,as a result of the"soften"effect of fracturing fluid on shale.The results of this study provide a reliable reference point and data support for future research on the mechanical properties of Longmaxi shale rocks. 相似文献
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日本本州及其邻近区域的应力状态以及弧后盆地的演化机制一直是人们所关注的问题.本文对2011年3月11日东日本大地震地震序列(2011年3月11日至2012年3月15日)的哈佛双力偶解进行了聚类分析,得到五种类型的震源机制解:与主震类型一致的低倾角逆断层型地震;主张应力方向垂直于日本海沟走向的正断层型地震;主张应力方向平行于日本海沟走向的正断层型地震;主压应力方向平行于日本海沟走向的逆断层型地震;包括走滑型地震在内的其他类型地震.东日本大地震地震序列中发生在弧前增生楔地震的震源机制解与大地震发生之前地震的震源机制解特征有显著区别,反映出该地区的应力状态与震前相比有较大改变.东日本大地震及其前震释放了附近区域的累积弹性应力,主震破裂区附近太平洋板块和其上覆板块接近完全解耦,降低了日本海盆地、中国东北地区的近东西向挤压应力水平.不过,整个本州岛东部区域太平洋板块和其上覆板块并没有完全解耦,但应力水平并不高.我们认为,日本海及中国东北应力水平的降低会使该区域的近东西向挤压型地震的危险性降低,而使NNE-SSW走向的走滑型地震活动性增强.同时,火山活动性也会增强.尤其是本州岛地区,存在近期火山爆发的可能性.东日本大地震地震序列的震源机制解特征还提示我们,日本海的应力状态及日本海的演化可能在一定程度上取决于太平洋板块和上覆板块的耦合状态.持续的弱耦合将不仅使得弧后大范围的地区保持岩浆上涌所必须的拉伸应力环境,而且还会因弧前隆起区发育大量正断层型地震而向深部提供促使岩浆生成所必须的水,因而造成日本海的再次扩张. 相似文献
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设计了含圆柱形障碍体的平直断层物理模型，在概念上可模 拟断层面上与地震孕育相关的障碍体等强固区域. 开展了中等尺度岩石标本的双轴压缩实验 ，研究标本在变形过程中群体微破裂事件的时空演化. 结果表明：(1)由于标本预置断层两 盘与障碍体之间、以及断层两盘彼此之间复杂的相互作用，使得交替活动成为含障碍体平直 断层标本变形过程中最为显著的特征； (2)含障碍体平直断层标本能够发生动力学失稳的前 提条件是障碍体在外加载荷作用下首先发生破坏，微破裂群体在障碍体破坏前后显示不同的 时空演化特征；(3)含障碍体平直断层标本失稳前的总变形量较大，弹性变形阶段微破裂累 积频次呈指数增长. 而在其后的位移弱化阶段，在障碍体及围绕障碍体的围岩区域内微破裂 事件稀少，突发失稳发生在相对平静的背景之上；(4)不同构造组合变形过程中的微破裂群 体具有明显不同的b值，b值与构造相关的区域性差异是明显的. 相似文献
18.
Guo Liangqian 《中国地震研究》2000,14(4):312-322
In the paper, the current strain field and stress field in Chinese continent have been discussedbased on the processed data from two GPS campaigns of national GPS network carried out inthe years of 1994 and 1996. With a principal compressional strain direction of NNE, thewestern and castern parts of Qinghai-Xizang subplate are dominated by extensional straiu andthe central Part by compressional strain. Along the southwestern segment of southeastern partof Qinghai-Xizang subplate, i. e. Yunnan area, the princiPal compressional strain direction isNW and the compressional strain is equivalent to the extensional strain in magnitude. Theprincipal compressional strain of Xinjiang subplate is mainly NNE and NE with a difference inthe strain magnitude. The principal compressional strain in North China subplate is quite effective in NE and nearly EW directions with differences along some segments. However, thecompressional strain is corresponding to the extensional strain in magnitude in most areas. Theprincipal 相似文献
19.
声发射观测是岩石摩擦实验中研究强震孕育机制的重要观测手段之一.传统的声发射观测以触发记录为主,难以捕捉并提取微弱的声发射信号.近年来天然地震学中发展的模板匹配技术可以在连续波形记录中识别出微弱的事件,大大提升事件检测能力.本文发展了适用于多通道连续记录的声发射信号的模板匹配技术,并将该技术应用于分析米尺度岩石断层黏滑失稳过程.研究结果显示:模板匹配技术识别出的声发射数量约为传统方法识别的5倍,相对完备震级降低约0.3.临近失稳,检测目录完备震级以上声发射率表现出幂律增加的特征,且声发射事件聚集在失稳破裂起始点附近.失稳后,检测目录完备震级以上声发射率表现出幂律衰减,其中失稳后早期表现出较慢的衰减速度.另外,失稳后早期声发射事件表现出随对数时间沿断层迁移的趋势.最后,通过与天然地震学观测的结果对比表明,声发射模板匹配识别技术是研究大尺度岩石摩擦滑动失稳过程中前震和余震时空演化规律的有效手段,该技术助于在方法上为室内实验和野外观测进行融合研究提供思路. 相似文献
20.
基于岩石变形声发射实验结果讨论了大震前地震活动平静现象的机制。在双轴压缩、等位移速率加载条件下 ,挤压型雁列断层、含宏观凹凸体断层、Ⅲ型剪切断层等非连续断层在临近滑动失稳前 ,声发射活动均出现了明显的相对平静现象 ,表现为声发射事件的发生率和应变能释放水平显著降低。与此阶段相对应 ,断层带 (特别是非连续部位上新形成的一小段断层 )发生了蠕滑和匀阻化作用 ,并使得标本的差应力开始下降。根据实验结果提出 ,大地震前断层的“蠕滑 -匀阻化”过程是造成地震活动平静现象的可能机制 相似文献