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1.
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
2.
Using Particle Flow Code, a discrete element model is presented in this paper that allows direct modeling of stick-slip behavior in pre-existing weak planes such as joints, beddings, and faults. The model is used to simulate a biaxial sliding experiment from literature on a saw-cut specimen of Sierra granite with a single fault. The fault is represented by the smooth-joint contact model. Also, an algorithm is developed to record the stick-slip induced microseismic events along the fault. Once the results compared well with laboratory data, a parametric study was conducted to investigate the evolution of the model’s behavior due to varying factors such as resolution of the model, particle elasticity, fault coefficient of friction, fault stiffness, and normal stress. The results show a decrease in shear strength of the fault in the models with smaller particles, smaller coefficient of friction of the fault, harder fault surroundings, softer faults, and smaller normal stress on the fault. Also, a higher rate of displacement was observed for conditions resulting in smaller shear strength. An increase in b-values was observed by increasing the resolution or decreasing the normal stress on the fault, while b-values were not sensitive to changes in elasticity of the fault or its surrounding region. A larger number of recorded events were observed for the models with finer particles, smaller coefficient of friction of the fault, harder fault surroundings, harder fault, and smaller normal stress on the fault. The results suggest that it is possible for the two ends of a fault to be still while there are patches along the fault undergoing stick-slips. Such local stick-slips seem to provide a softer surrounding for their neighbor patches facilitating their subsequent stick-slips. 相似文献
3.
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
4.
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
5.
Finite Element Analysis of Fault Bend Influence on Stick-Slip Instability along an Intra-Plate Fault
— Earthquakes have been recognized as resulting from stick-slip frictional instabilities along the faults between deformable rocks. A three-dimensional finite-element code for modeling the nonlinear frictional contact behaviors between deformable bodies with the node-to-point contact element strategy has been developed and applied here to investigate the fault geometry influence on the nucleation and development process of the stick-slip instability along an intra-plate fault through a typical fault bend model, which has a pre-cut fault that is artificially bent by an angle of 5.6° at the fault center. The numerical results demonstrate that the geometry of the fault significantly affects nucleation, termination and restart of the stick-slip instability along the intra-plate fault, and all these instability phenomena can be well simulated using the current finite-element algorithm. 相似文献
6.
The nucleation process of stick-slip instability was analyzed based on the experimental measurements of strain and fault slip on homogeneous and non-homogeneous faults. The results show that the nucleation process of stick-slip on the homogeneous fault is of weak slip-weakening behavior under constant loading point velocity. The existence of a short "weak segment" on the fault makes slip-weakening phenomenon in nucleation process more obvious, while the existence of a long "weak segment" on the fault makes the nucleation process changed. The nucleation is characterized by accelerating slip in a local region and rapid increase of shear stress along the fault in this case, which is more coincident with the rate and state friction law. During the period when fault is locked, increasing of shear stress causes lateral elastic dilation near the fault, and the rebound of the dilation at the time of instability causes an instantaneous increase of normal stress in the fault plane, which is an important factor making fault be rapidly locked and its strength recovered. 相似文献
7.
8.
Nicholas W. Hayman Lucie Ducloué Kate L. Foco Karen E. Daniels 《Pure and Applied Geophysics》2011,168(12):2239-2257
It is a long-standing question whether granular fault material such as gouge plays a major role in controlling fault dynamics
such as seismicity and slip-periodicity. In both natural and experimental faults, granular materials resist shear and accommodate
strain via interparticle friction, fracture toughness, fluid pressure, dilation, and interparticle rearrangements. Here, we
isolate the effects of particle rearrangements on granular deformation through laboratory experiments. Within a sheared photoelastic
granular aggregate at constant volume, we simultaneously visualize both particle-scale kinematics and interparticle forces,
the latter taking the form of force-chains. We observe stick-slip deformation and associated force drops during an overall
strengthening of the shear zone. This strengthening regime provides insight into granular rheology and conditions of stick-slip
periodicity, and may be qualitatively analogous to slip that accompanies longer term interseismic strengthening of natural
faults. Of particular note is the observation that increasing the packing density increases the stiffness of the granular
aggregate and decreases the damping (increases time-scales) during slip events. At relatively loose packing density, the slip
displacements during the events follow an approximately power-law distribution, as opposed to an exponential distribution
at higher packing density. The system exhibits switching between quasi-periodic and aperiodic slip behavior at all packing
densities. Higher packing densities favor quasi-periodic behavior, with a longer time interval between aperiodic events than
between quasi-periodic events. This difference in the time-scale of aperiodic stick-slip deformation is reflected in both
the kinematics of interparticle slip and the force-chain dynamics: all major force-chain reorganizations are associated with
aperiodic events. Our experiments conceptually link observations of natural fault dynamics with current models for granular
stick-slip dynamics. We find that the stick-slip dynamics are consistent with a driven harmonic oscillator model with damping
provided by an effective viscosity, and that shear-transformation-zone, jamming, and crackling noise theories provide insight
into the effective stiffness and patterns of shear localization during deformation. 相似文献
9.
10.
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
11.
帕米尔高原位于地中海－喜马拉雅地震带上,晚新生代以来随着印度板块向欧亚板块持续不断地挤压汇聚,其构造运动是欧亚大陆最强烈的地区。高原腹地发育一系列近SN向正断层,包括近SN向的塔什库尔干正断层所处的帕米尔中部现代区域的构造应力场以EW向水平拉张为主。2016年11月25日发生的阿克陶MS 6.7级地震的发震构造为塔什库尔干断层分支的NWW向木吉盆地北缘断层,其具有右旋走滑兼正断性质。地震在震中附近产生同震地表形变带,全长约1km,呈近SN－NNE向水平拉伸,发育近EW—NWW向的张裂缝,为地震破裂的产物,张裂缝的最大水平拉伸位移量和最大垂直位移量分别为46cm和16cm。地表破裂带中的NE和NW向张剪裂缝只是连接贯通这些雁列的张裂缝,其水平相对位移量取决于张裂缝的水平拉伸量和张裂缝之间的几何关系。地表形变带表现的拉张性质与帕米尔高原腹地区域现代应力场最大主压应力为垂直向基本一致,可能与深部热物质上涌造成的上地壳拉伸有关。而地表形变带呈近SN向水平拉张,与区域近EW向拉张应力场之间存在显著差异,这可能是木吉盆地北缘右旋走滑正断层阶区局部应力场调整的结果。 相似文献
12.
用双剪法对济南辉长岩和点苍山大理岩进行了摩擦滑动实验.实验中的应力变化方式有两种.A 型实验:先使断层面上的正应力增加到一定值,然后保持正应力不变,并增加剪应力使断层发生粘滑;B 型实验:先使断层面上的正应力增加到一定的值,保持正应力不变,并增加剪应力到断层发生粘滑前的某一应力状态,再保持剪应力不变,减小正应力直到粘滑发生.实验表明,B 型实验中岩石的摩擦强度高于 A 型实验.A 型实验中粘滑发生前有声发射率增加的前兆,B 型实验中粘滑发生前看不到声发射率的明显增加.由实验得到一个启示,即闭锁断层的开锁可能采取两种形式:一种是冲开闭锁,即以剪应力的增加使断层发生错动;另一种是解开闭锁,即以正应力的减小使断层发生错动.断层的粘滑采取哪种形式,由断层带的应力变化途径决定. 相似文献
13.
Slip- and Time-dependent Fault Constitutive Law and its Significance in Earthquake Generation Cycles 总被引：1，自引：0，他引：1
-- By integrating effects of microscopic interactions between statistically self-similar fault surfaces, we succeeded in deriving a slip- and time-dependent fault constitutive law that rationally unifies the slip-dependent law and the rate- and state-dependent law. In this constitutive law the slip-weakening results from the abrasion of surface asperities that proceeds irreversibly with fault slip. On the other hand, the restoration of shear strength after the arrest of faulting results from the adhesion of surface asperities that proceeds with contact time. At the limit of high slip-rate the unified constitutive law is reduced to the slip-weakening law. At the limit of low slip-rate it shows the well-known log t strengthening of faults over the wide range of contact time t. In the steady state with a constant slip-rate V the shear strength has the negative log V dependence, known as the velocity-weakening. Another important property expected from the unified constitutive law is the gradual increase of the critical weakening displacement Dc with stationary contact time. We numerically examined behavior of a single degree of freedom elastic system following the slip- and time-dependent constitutive law, and found that the periodic stick-slip motion is realized when the adhesion rate is high in comparison with the loading rate. If the adhesion rate is very low, behavior of the system gradually changes from stick-slip motion to steady sliding with time. 相似文献
14.
Shengli Ma Liqiang Liu Jin Ma Kaiying Wang Xiaoyan Hu Tianchang Liu Xiuquan Wu 《中国科学D辑(英文版)》2003,46(2):56-66
The nucleation process of stick-slip instability was analyzed based on the experimental measurements of strain and fault slip on homogeneous and non-homogeneous faults. The results show that the nucleation process of stick-slip on the homogeneous fault is of weak slip-weakening behavior under constant loading point velocity. The existence of a short “weak segment” on the fault makes slip-weakening phenomenon in nucleation process more obvious, while the existence of a long “weak segment” on the fault makes the nucleation process changed. The nucleation is characterized by accelerating slip in a local region and rapid increase of shear stress along the fault in this case, which is more coincident with the rate and state friction law. During the period when fault is locked, increasing of shear stress causes lateral elastic dilation near the fault, and the rebound of the dilation at the time of instability causes an instantaneous increase of normal stress in the fault plane, which is an important factor making fault be rapidly locked and its strength recovered. 相似文献
15.
The geometry of faults at seismogenic depths and their continuation into the ductile zone is of interest for a number of applications ranging from earthquake hazard to modes of lithospheric deformation. Teleseismic passive source imaging of faults and shear zones can be useful particularly where faults are not outlined by local seismicity. Passive seismic signatures of faults may arise from abrupt changes in lithology or foliation orientation in the upper crust, and from mylonitic shear zones at greater depths. Faults and shear zones with less than near-vertical dip lend themselves to detection with teleseismic mode-converted waves (receiver functions) provided that they have either a contrast in isotropic shear velocity (V s), or a contrast in orientation or strength of anisotropic compressional velocity (V p). We introduce a detection method for faults and shear zones based on receiver functions. We use synthetic seismograms to demonstrate common features of dipping isotropic interfaces and contrasts in dipping foliation that allows determination of their strike and depth without making further assumptions about the model. We proceed with two applications. We first image a Laramide thrust fault in the western U.S. (the Wind River thrust fault) as a steeply dipping isotropic velocity contrast in the middle crust near the surface trace of the fault; further downdip and across the range, where basin geometry suggests the fault may sole into a subhorizontal shear zone, we identify a candidate shear zone signal from midcrustal depths. The second application is the use of microstructural data from exhumed ductile shear zones in Scotland and in the western Canadian Shield to predict the character of seismic signatures of present-day deep crustal shear zones. Realistic anisotropy in observed shear fabrics generates a signal in receiver functions that is comparable in amplitude to first-order features like the Moho. Observables that can be robustly constrained without significant tradeoffs are foliation strike and the depth of the foliation contrast. We find that an anisotropy of only a few percent in the shear zone is sufficient to generate a strong signal, but that the shear zone width is required to be >2 km for typical frequencies used in receiver function analysis to avoid destructive interference due to the signals from the boundaries of the shear zone. 相似文献
16.
17.
Emilio Rodríguez-Escudero José J. Martínez-Díaz José A. Álvarez-Gómez Juan M. Insua-Arévalo Ramón Capote del Villar 《Bulletin of Earthquake Engineering》2014,12(5):1831-1854
In this work we analyze the tectonic setting of the recent damaging seismic series occurred in the Internal Zones of the eastern Betic Cordillera (SE Spain) and surrounding areas, the tectonic region where took place the 11th May 2011 Mw 5.2 Lorca earthquake. We revisit and make a synthesis of the seven largest and damaging seismic series occurred from 1984 to 2011. We analyze their seismotectonic setting, and their geological sources under the light of recent advances in the knowledge on active faults, neotectonics, seismotectonics and stress regime, with special attention focused on the Lorca Earthquake. These seismic series are characterized by two types of focal mechanisms, produced mainly by two sets of active faults, NNW–SSE to NNE–SSW small (no larger than 20–30 km) extensional faults with some strike slip component, and E–W to NE–SW large strike slip faults (more than 50 km long) with some compressional component (oblique slip faults). The normal fault earthquakes related to the smaller faults are dominant in the interior of large crustal tectonic blocks that are bounded by the large E–W to NE–SW strike-slip faults. The strike slip earthquakes are associated to the reactivation of segments or intersegment regions of the large E–W to NE–SW faults bounding those crustal tectonic blocks. Most of the seismic series studied in this work can be interpreted as part of the background seismicity that occurs within the crustal blocks that are strained under a transpressional regime driven by the major strike slip shear corridors bounding the blocks. The seismotectonic analysis and the phenomenology of the studied series indicate that it is usual the occurrence of damaging compound earthquakes of M \(\sim \) 5.0 associated with triggering processes driven by coseismic stress transfer. These processes mainly occur in the seismic series generated by NNW–SSE to NNE–SSW faults. These mechanical interaction processes may induce a higher frequency of occurrence of this kind of earthquakes than considered in traditional probabilistic seismic hazard assessments and it should be taken into account in future seismic hazard assessments. 相似文献
18.
The faiture of pre-existing faults was studied experimentally and theoretically. The stress concentration around open and healed slits in plexiglas under uniaxial stress was calculated and compared to observations by Schlieren photographs. The rupture velocities along these pre-existing faults were found to vary from 0.25 of the shear velocity up to velocities slightly exceeding the shear velocity. Sudden fault dislocation was often preceded by stable sliding. The amplitudes of elastic waves radiated in the forward quadrant of the rupture were larger than the amplitudes in the backward quadrant. 相似文献
19.
为提高穿越黏滑断层隧道的结构安全性和稳定性,开展了正断层黏滑错动作用下隧道抗错断措施作用效果室内模型试验。通过分析结构纵向应变、接触压力及安全系数,对未采取措施、结构加强、结构加强并施设减错层、结构加强并施设减错缝、结构加强并施设减错层和减错缝5种工况进行了对比分析。研究结果表明:采用减错措施（减错层/缝或减错层+减错缝）后,沿隧道纵向结构纵向应变、接触压力增加倍数由剧烈变化变为较均匀变化;仅采用结构加强措施抵抗正断层黏滑错动对隧道结构的影响,效果有限;通过采用减错措施消减正断层黏滑错动对隧道结构的影响,效果明显,结构安全系数最小值增加8倍以上;通过采用结构加强并施设减错层和减错缝措施抵抗和消减正断层黏滑错动对隧道结构的影响,效果显著,结构安全系数最小值增加25.45倍。研究成果可为高烈度艰险山区黏滑正断层隧道的抗错断设防设计提供参考。 相似文献
20.
A new seismic energy dissipation shear wall structure is proposed in this paper. The new shear wall is one with purposely built‐in vertical slits within the wall panel, and rubber belts as seismic energy dissipation devices are installed in the vertical slits. In order to verify this concept, shaking table tests of a 10‐storey shear wall model with rubber belts filled in the vertical slits were carried out, and comparison of seismic behaviour was made between the new shear wall system and a shear wall with reinforced concrete connecting beams as energy dissipation. Furthermore, the seismic behaviour of this new shear wall is analysed by a finite element time history analysis method. The test and analysis show that the new shear wall system has a very good ability to dissipate seismic energy and is easy to use in engineering practice. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献