共查询到20条相似文献，搜索用时 31 毫秒
1.
S. D. Vinogradov 《Pure and Applied Geophysics》1978,116(4-5):888-899
Elastic waves were recorded from tensile cracks and prepared shear faults in the laboratory. The velocity of tensile crack propagation was measured. The duration of crack propagation was correlated with the signal pulse duration. Experiments with prepared shear faults showed that obstacles on the fault change the pulse form and the relation between wave amplitude (magnitude) and seismic moment. 相似文献
2.
Jan Kozák Jan Šílený Ludvík Waniek Reviewer V. Červený 《Studia Geophysica et Geodaetica》1981,25(4):332-342
Summary Tensile cracks induced by stress concentration around a fault plane in physical models under uniaxial load were analyzed. The results characterizing the decisive role of the fault plane inclination to the the stress direction are presented. Two stages of tensile crack life were determined, i.e. the first, seismoactive stage, accompanied by seismic energy release and the second aseismic one characterized by low velocity of crack propagation. Results obtained seem to be relevant to a better understanding of the character and regime of actual seismoactive faults. 相似文献
3.
在研究地震孕育及震源破裂的问题时,用三维破裂来模拟地震破裂过程,比二维破裂与实际更加接近。我们设计了一组实验,采用几种不同的材料（玻璃、有机玻璃和大理石等）做成平板试件,在其中心预制非穿透裂纹,并在单轴压下进行了实验研究。 实验结果表明,非穿透裂纹与穿透裂纹的扩展情况有质的差别。非穿透裂纹的扩展并不沿原裂纹面延伸,而是沿裂纹前缘扩展出许多裂纹面,每一个破裂面都是复杂的扭曲、拐折的曲面。这可能意味着实际地震断层的扩展情况也是极为复杂的。 相似文献
4.
G. A. Sobolev 《Pure and Applied Geophysics》1986,124(4-5):811-824
One of the simplest models of earthquakes and rockbursts was studied in laboratory conditions in which the fracture was initiated in a barrier between two preexisting faults. The treated models were built of concrete; during the construction of the models, the stress concentrators were inserted inside the models. This arrangement enabled the shear displacement to occur during uniaxial loading of the model. The tests were made on the series of models, the sizes of which were mutually varying more than one order. In the process of the barrier fracture propagation, the following were investigated: the time and space changes of local deformations as well as the acoustic emission, velocities and amplitudes of elastic waves, electrical conductivity and proper electro-induction. The process of barrier fracturing can be understood in three fundamental stages. In the course of the first stage, the density of small tensile cracks increases considerably, while the volume in which they exist is gradually enlarged. In the second stage, as the result, of these cracks coupling, longer shear cracks are created. During the coupling, due to the development of numerous regions of unstable deformation, the zones of nonequal rigidity arise in the treated medium, distributed within it in a mosaic-like pattern. In the third stage, the main fracture is prepared and formed with simultaneous unloading of the surrounding medium. The process of crack forming is gradually localized into a more narrow zone.The second and third stages of fracture forming are reflected in variations of all the above-mentioned physical parameters which are therefore identified as the precursors of the main fracture. By means of the series of precursors it is possible to find the reliable prediction of a barrier fracture. 相似文献
5.
The role of the chemical environment in frictional deformation: Stress corrosion cracking and comminution 总被引：23，自引：0，他引：23
The roles of chemically assisted crack and fracture propagation and chemically assisted comminution in frictional deformation are evaluated in this study. Double cantilever beam (DCB) crack propagation data are presented which show that the role of pH in chemically assisted fracture, and to a lesser extent the role of ionic concentration are important in stress corrosion cracking. Data on very slow crack growth and the stress corrosion limit are also presented. These data suggest that stress corrosion cracking may play an important role in compound earthquakes and in asperity breakdown in faults. The comminution literature is also reviewed in order to assess the role of chemically assisted comminution in frictional deformation. It appears that chemically assisted comminution may be important at low and high ionic strength because it may reduce the effective viscosity and the shear strength of fault gouge. At intermediate ionic concentration the role of pH, as an agent which enhances crack and fracture propagation, appears to be more important in reducing the coefficient of sliding friction. 相似文献
6.
本文讨论了利用破裂力学理论说明地震破裂的过程, 认为地震本质上是岩石在应力作用下的低应力破裂现象.它是岩石中的裂纹不断稳态扩展、最后进入失稳扩展的结果.分析了在扩展过程中应力和位移的变化, 发现任何将要破裂的那一点的应力都要由初始应力0升高到屈服应力y 以后才破裂, 破裂后裂纹面上的点的应力降到0.在破裂前和破裂后的位移, 都可由弹性力学方程给出.在破裂的一瞬间破裂的端点产生的非弹性位移, 则不能由弹性力学方程给出.它可以由断裂力学中的裂纹滑开位移公式近似给出.根据位错模式由于计算弹性波辐射场的位错量 D(, t), 正是破裂瞬间产生的非弹性位移, 所以用弹性位移公式来计算地震位错量是错误的.我们采用了裂纹滑开位移公式来计算地震位错量, 从而导出了较合理的计算地震释放总能量的公式 ET=yDS(y 为屈服强度;D为平均位错;S 为断层面积)以及估算初始应力值0的公式:0 =[Dmax/L4y/(1-) ]1/2(L 为断层长度).用它们计算了一些地震的 Er 和0, 分别列于表1和表2.这些结果比以往的结果要更合理一些。 结果表明:(1)地震多数是在低应力作用下(即低初始应力)发生的(约100——200巴);(2)地震释放的总能量约比地震波能量大一个数量级. 相似文献
7.
K. B. Broberg 《Pure and Applied Geophysics》2006,163(9):1867-1879
Although mode I and mode II crack propagation show many similarities, in particular when analysed by linear elastic fracture
mechanics, they differ significantly in the micro-structural behaviour. These differences, which are clearly noticeable in
the fracture surface morphology, lead to fundamental differences in the macroscopic behaviour. Thus, mode II crack expansion
under remote loading, appears to obey micro-structural scaling laws, implying that the dimensions of the process region stay
essentially constant during crack expansion, rather than increasing with crack length. Therefore, expanding mode II cracks
can almost reach the Rayleigh velocity, and actually also intersonic velocities. An expanding mode I crack, on the other hand,
seems to obey continuum scaling laws, implying that the dimensions of the process region increase in proportion to crack length,
leading to self-similar crack expansion at a velocity significantly below the Rayleigh speed and dependent on the remote load. 相似文献
8.
L. N. Germanovich R. L. Salganik A. V. Dyskin K. K. Lee 《Pure and Applied Geophysics》1994,143(1-3):117-149
9.
为了解决采用Trimble GX 3D地面激光三维扫描仪分析互层胶结土中正断层地震地表破裂位错特征时,未有效模拟地表垂直和水平位移的基本特征,获取的地表破裂位错特征结果不准确的问题。提出新的互层胶结土中正断层地震地表破裂位错特征研究方法,先构建地震地表弹性位错模型,分析互层胶结土正断层的地表三维断裂特征,得到地表在受到走滑、逆冲和张开错动导致的地表错位变化情况;再通过正断层地震地表破裂离心机试验,获得互层胶结土中正断层地震地表破裂位错特征。试验结果说明,所提方法可有效分析互层胶结土中正断层地震地表破裂位错特征,且破裂点在土体模型中部和中下部的裂缝深度分别为22.4 m和33.4 m,裂缝上的破裂点处于土体模型的中下部时,裂缝的深度越深。 相似文献
10.
The previously developed two-dimensional boundary element procedure for analysing the propagation of a single discrete crack is extended to simultaneous multiple cracking in concrete gravity dams. A brief discussion of the generalized methodology is presented and the validity of the extended procedure is verified by performing a fracture analysis of the Fongman dam and comparing the predicted rupture process with the available experimental results. The fracture response of the Koyna dam is then studied extensively under the Koyna earthquake. Both single and multiple cracking models are employed to investigate the fracture process as well as final rupture in the dam. Similar final damage involving complete separation of the crest block of the dam is predicted, irrespective of whether single or multiple crack propagation models are employed. In relation to the phenomenon of hydrodynamic uplift pressure within propagating cracks, openings of the crack on the upstream face of the dam are examined in particular. The results indicate that this phenomenon is not expected to be significant during the crack development phase, and hence unlikely to affect the final rupture characteristics of dams undergoing strong earthquake excitation. 相似文献
11.
本文研究了1981年1月23日发生在四川道孚的Ms=6.8级地震和1983年2月13日发生在新疆乌恰的Ms=6.2级地震以及与它们相连系的有关地震的破裂扩展过程。本文除用体波资料研究外,主要是从断裂扩展和终止的角度,用单断裂和断裂系的力学模式从理论和试验方面分别模拟了这些地震破裂扩展的全过程,并研究了这些地震序列本身以及它们和周围地震的空间分布关系。因此提出了能更可靠地确定地震破裂面的几何尺度,确定地震断层的活动段和闭锁段的位置和长度的一种新方法,简称为扩展过程的拐折点方法。该方法还能解释和判断在不同断层部位发生的那些地震所具有的震源力学特征。并初步将该方法应用于鲜水河断裂带的地震趋势分析。 相似文献
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13.
基于能量耗散理论建立非均质岩石的动态损伤破坏元胞自动机,分析单轴压缩试验中岩石破坏截面的损伤状态,得到该情况下的岩石裂隙微观动态发展过程、损伤演化关系以及全程应力应变曲线。研究发现：①加载过程中,均质度较低的岩样裂纹的萌生和扩展较为分散,损伤速率低;均质度较高的岩样裂纹的萌生和扩展非常集中,表现为脆性破坏。②损伤演化曲线呈3阶段S形发展。③随着岩石均质度参数的增加,岩石的峰值强度和峰值应变都有所提高,峰后曲线越来越陡。④给出的衡量岩石脆性破坏强弱程度的指标参数,能够较好地描述岩石破坏形式随着均值度参数m变化的规律。 相似文献
14.
A special experimental technique enabled us to study in detail seismic events on a fault model in a uniaxial stress field. The recording system used made it possible to investigate the radiation pattern for all the events observed including the precise determination of the dislocation origin.The aim of the present paper is (1) to find the relation between shear and tensile displacements, (2) to check a possible influence of the process of tensile crack generation on the seismic energy release and (3) to compare the seismic regime of a single fault before and after the tensile crack generation, respectively.Results prove the dominating importance of shear mechanism for the seismic energy release. The tensile displacement can be seismoactive only under special contact conditions on the fault plane.The existence of tensile cracks at the fault tips changed the pattern of seismic energy radiation. This feature is probably caused by subsequent changes in contact conditions on the fault plane and in the stress field around the fault.A comparison of some results of the present model experiments with the already published results of geological and seismological measurements and investigations shows the analogous character in laboratory and in nature of the process of tectonic earthquake preparation, the displacement course on the fault during the earthquake and the manner of seismic energy release on faults. 相似文献
15.
Slip synergism of planar strike-slip fault during meta-instable state: Experimental research based on digital image correlation analysis 总被引：2，自引：0，他引：2
The meta-instable state (MIS) is the final stage before fault instability during stick-slip movement. Thus, identification of MIS is of great significance for assessing earthquake hazard in fault zones. A rock sample with a precut planar fault was loaded on a horizontally biaxial servo-controlled press machine to create stick-slip conditions. Digital images of the sample surface were taken by a high-speed camera at a rate of 1000 frames per second during the stick-slip motion and processed using a 2D digital image correlation method to obtain the displacement field. We define a synergism coefficient that describes the relative dispersion of the accumulative fault slip. The results reveal that: (1) a local pre-slip area spreads very slowly along the fault before the MIS develops. It extends at a higher but still slow speed during meta-instable state I (MIS-I). During the final ～1.5% of MIS, in meta-instable state II (MIS-II), the local pre-slip area first extends at a speed of ～0.9 m/s, and then expands out of the observed image area at a very high speed. These results indicate that the local pre-slip area transforms from a state of quasi-static extension in MIS-I to quasi-dynamic extension in MIS-II. (2) The synergism coefficient of the fault slip decreases to half of its original value in MIS-I and to a quarter of its original value in MIS-II. This continuous decrease of synergism coefficient indicates that the strengthening of fault slip synergism is a characteristic of MIS. (3) Furthermore, the unstable sliding stage includes three sliding processes: initial-, fast-, and adjusted-sliding. There are two pauses between the three sliding processes. 相似文献
16.
Tertiary basaltic pillow lobes at Cape Grim, northwestern Tasmania, Australia display well-preserved spreading cracks in the glassy crust. The spreading cracks are lens-shaped or rectangular in plan view. In cross section, they consist of a graben-like depression with a broad floor bounded by steep scarps. The floor of spreading crack contains an axial crack and a number of ridges that are arranged symmetrically with respect to the axial crack. The ridges within spreading cracks are inferred to have formed by the regular, repeated production and splitting of new crust at the centre of the spreading crack. This new interpretation of ridges in spreading cracks differs from the previous interpretation in which they are regarded as elongate normal fault blocks. Our interpretation provides new insight into the propagation mechanisms of pillow lavas. 相似文献
17.
This paper focuses on the propagation and dynamic effects of blast waves in faulted rock masses. A coupled method combining UDEC and LS-DYNA is presented whereby the explosion process is simulated by LS-DYNA while the wave propagation and its dynamic effects in rock masses with faults are modeled by UDEC. The blast-induced crack evolution and failure zone distribution in faulted rock masses are explored using the proposed coupled method. The relationship between rock failure and fault parameters such as dip, stiffness and friction are also investigated. The results indicate that the coupled method is feasible and effective for evaluating explosion in discontinuous rock system and the existence of faults exerts significant influence on the pattern of rock masses failure. 相似文献
18.
本实验研究了地壳内对压组合构造和对张组合构造中垂断层蠕滑,破裂错动时对主震断层(底断层)应力积累过程的影响,并结合实际地震活动中的一些现象进行了讨论。所得结论如下: 1.当垂断层蠕滑时,对压组合构造中垂直于底断层的压应力增大,它可以延迟主震发生但增大发震的能量;对张组合构造中垂直于底断层的压应力减小,剪应力略有增大,因而可以促使主震发生。2.如果垂断层某一部分为原来锁住的愈合断层或为完整介质,当其突然破裂错动时,可以使对张组合构造中的底断层的剪应力突然增大,同时压应力减小,因此前震序列中这类垂断层上的较大前震可看作底断层上主震即将来临的信号。3.由垂断层破裂前后单轴压力不变和位移不变的实验结果说明了地壳中主震断层应力集中的过程。4.底断层的主震破裂可以使处于引张状态的垂断层上余震发育甚至发生强余震。本文还应用实验结果对前震活动的条带现象进行了解释,这将有助于判定对压组合构造中主震的断层面。 相似文献
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I. R. Stakhovsky 《Izvestiya Physics of the Solid Earth》2011,47(5):371-378
Geometric characteristics of fractal sets of cracks are investigated from the standpoint of their coalescence. A 1D computer
model, in which a realistic character of forms of crack sets is achieved through the inducing of sets with the use of the
multiplicative cascade procedure, is considered. The investigation is aimed at the determination of conditions of coalescence
of cracks organized as a superposition of fractal subsets of a unified set of cracks. The process of crack coalescence is
investigated for three different values of the coalescence criterion. The geometric characteristics of the sets of cracks
that are necessary for the transition of the crack coalescence process into an avalanche-like stage are estimated. 相似文献