共查询到20条相似文献，搜索用时 31 毫秒
1.
This study considers the effects of heat transfer and fluid flow on the thernal, hydrologic, and mechanical response of a fault surface during seismic failure. Numerical modeling techniques are used to account for the coupling of the thermal, fluid-pressure, and stress fields. Results indicate that during an earthquake the failure surface is heated to a tempeature required for the thermal expansion of pore fluids to balance the rate of fluid loss due to flow and the fluid-volume changes due to pore dilatation. Once this condition is established, the pore fluids pressurize and the shear strength decreases rapidly to a value sufficient to maintain the thermal pressurization of pore fluids at near-lithostatic values. If the initial fluid pressure is hydrostatic, the final temperature attained on the failure surface will increase with depth, because a greater pressure increase can occur before a near-lithostatic pressure is reached. The rate at which thermal pressurization proceeds depends primarily on the hydraulic characteristics of the surrounding porous medium, the coefficient of friction on the fault surface, and the slip velocity. If either the permeability exceeds 10–15 m2 or the porous medium compressibility exceeds 10–8 Pa–1, then frictional melting may occur on the fault surface before thermal pressurization becomes significant. If the coefficient of friction is less than 10–1 and if the slip velocity is less than 10–2 msec–1, then it is doubtful that either thermal pressurization or frictional melting on the fault surface could cause a reduction in the dynamic shear strength of a fault during an earthquake event. 相似文献
2.
简述了最近20年来国内外岩石高速摩擦实验研究领域的进展和动态:岩石高速摩擦实验技术的发展实现了对高滑动速率、大位移的地震过程的实验模拟;其结果揭示了岩石和断层泥在地震滑动速率下的力学性状,深化了对断层滑动弱化机制、临界滑动距离、以及地震发生过程的认识和理解;实验在假玄武玻璃成因方面取得了重要进展,并提出了断层发生地震滑动可能留下的其它地质证据,可望为研究断层滑动性状与地震物理过程提供新的思路和信息.岩石高速摩擦实验今后的发展方向主要包括:发展具有加温系统和孔隙压系统的岩石高速摩擦实验装置,研究水热作用下岩石和断层泥的高速摩擦性状;室内实验和地震资料分析相结合研究断层滑动和地震机制;室内实验和野外地质调查相结合探索断层发生地震错动的地质证据等等. 相似文献
3.
4.
Abstract The 1999 Chi-Chi earthquake in Taiwan ( M w = 7.6) produced a surface rupture along the north–south-striking Chelungpu thrust fault with pure dip-slip (east side up) and left lateral strike-slip displacements. Near-field strong-motion data for the northern part of the fault illustrate a distinct lack of the high-frequency seismic radiation associated with a large slip (10–15 m) and a rapid slip velocity (2–4 m/s), suggesting a smooth seismic slip associated with low dynamic frictional resistance on the fault. A drillhole was constructed at shallow depths in the possible fault zones of the northern part of the Chelungpu Fault, which may have slipped during the 1999 earthquake. One of the zones consists of a 20-cm-thick, unconsolidated fault breccia with a chaotic texture lacking both discrete slip surfaces (e.g. Riedel shears) and grain crushing. Other possible fault zones are marked by the narrow (less than a few centimeters) gouge zone in which clayey material intrudes into the damaged zone outside of the gouge zone. These characteristic fault rock textures suggest that the slip mechanisms at shallow levels during the earthquake involved either granular flow of initially unconsolidated material or slip localization under elevated pore pressure along the narrow clayey gouge zone. Because both mechanisms lead to low dynamic frictional resistance on the fault, the rapid seismic slip in the deep portions of the fault (i.e. the source region of strong-motion radiation) could have been accommodated by frictionless slip on the shallow portions of the fault. The combination of strong-motion data and fault rock analysis suggests that smooth slip associated with low dynamic friction occurred on both the deep and shallow portions of the fault, resulting in a large slip between the source region and the surface in the northern region. 相似文献
5.
Abstract The seismic slip that occurred during the 1999 Chi-Chi earthquake in Taiwan showed contrastive behaviors in different regions along the Chelungpu Fault: A large and smooth slip occurred in the north, while a relatively small slip associated with high-frequency seismic wave radiation occurred in the south. The core samples from shallow boreholes at northern (Fengyuan) and southern (Nantou) sites penetrating the seismic Chelungpu Fault were analyzed. The fault zones at the northern site are characterized by soft clayey material associated with clayey injection veins. This suggests that the fault zones were pressurized during ancient seismic slip events, and hence the elastohydrodynamic lubrication occurred effectively. In contrast, the fault rock from the southern site is old pseudotachylyte that has been shattered by repeated ancient seismic slip events. Statistical analysis of many pseudotachylyte fragments reveals that the degree of frictional melting tended to be low. In this case, the seismic slip is restrained by the mechanical barrier of a highly viscous melt layer. These contrastive fault rocks were produced by repeated ancient seismic slip events, but the two corresponding mechanisms of friction are likely to have also occurred during the 1999 Chi-Chi earthquake, thus causing the contrastive slip behaviors in the north and south. 相似文献
6.
本文对龙门山断裂带金河磷矿浅钻岩芯中的三种断层泥开展了低速到高速摩擦滑动的实验研究，并对实验变形样品开展了BET比表面积研究.摩擦实验在干燥和孔隙水压条件下开展，速率范围涵盖20 μm·s-1~1.4 m·s-1.实验结果显示，三种断层泥在干燥条件下的摩擦性质差别不大，但在孔隙水压条件下，三者的中低速摩擦强度与层状硅酸盐矿物的种类而非总含量紧密相关，蒙脱石和伊利石相比绿泥石更能有效地弱化断层.三种断层泥在孔隙水压条件下存在中低速率域的速度强化，暗示着对断层的加速滑动存在一定的阻碍作用.孔隙水压下，黄绿色和灰绿色断层泥的初始动态弱化非常迅速并伴随断层泥层的瞬时扩容，凹凸体急剧加热导致的局部热压作用可能是造成这种力学行为的物理机制.在经历高速滑动之后，三种断层泥在干、湿条件下的BET比表面积都显著降低，暗示着可能发生了颗粒烧结.中低速域内，孔隙水的存在使得断层泥呈现分散式的剪切变形，BET比表面积的增加因此比干燥条件下更加明显.对表面能的估算表明，颗粒磨碎所消耗的能量至多不超过摩擦力做功的8%，暗示着断层作用中颗粒磨碎所占的能量比例较低. 相似文献
7.
Akihiro Takeuchi Hiroyuki Nagahama 《Physics of the Earth and Planetary Interiors》2002,130(3-4):285-291
Fracturing and frictional sliding of quartz and granite under dry condition generates fractoluminescence, charged particle emission and electromagnetic radiation. Various kinds of experiments indicate that surface charge density on fracture or frictional slip surface of quartz and granite is 10−4 to 10−2 C/m2 which is larger than bound charges induced by the disappearance of piezoelectricity due to the release of stress. Hole and electron trapping centers, which is found in semiconductor devices with the Si–SiO2 system, are causes of surface charging on fracture or frictional slip surface of quartz crystal. The quantity of the surface charge is enough to cause corona discharge that can generate earthquake lights. The mechanism considering the hole and electron trapping centers has a probability to explain why non-piezoelectric minerals or rocks generate electromagnetic phenomena. It can be one of origins of seismo-electromagnetic phenomena (SEP). 相似文献
8.
THE VITRINITE REFLECTANCE OF FAULT ROCKS FROM THE WENCHUAN EARTHQUAKE FAULT ZONE: CONSTRAINTS ON FRICTIONAL PROPERTIES OF THE FAULT DURING THE EARTHQUAKE 
下载免费PDF全文
下载免费PDF全文 YAO Lu MA Sheng-li WANG Yu HE Hong-lin CHEN Jian-ye YANG Xiao-song SHIMAMOTO Toshihiko 《地震地质》2016,38(4):817-829
The temperature rise caused by frictional heating during seismic slip is able to indicate dynamic frictional properties of the seismic fault,which provides an approach to understand the dynamic process and energy budget of an earthquake.The residual indicators of frictional heating within the fault zone also can be taken as an evidence for seismic events.The vitrinite reflectance is a commonly-used geothermometer in the coal,oil and gas industries.It also has some potential applications in the studies of fault rock and fault mechanics.We studied vitrinite reflectance (VR) of fault rocks collected from surface outcrops of the Wenchuan earthquake fault zone in this paper.The measured data reveal that the VR of fault rocks are affected by fault motion,and there is a trend that the VR increases towards the fault core,which indicates the effects of frictional heating.The VR of fault rocks from the Bajiaomiao outcrop is much higher than those from the Shenxigou outcrop,which probably suggests the difference in fault activity at the two outcrops.Our study also suggests that systematic measurement of VR across the fault zone is helpful in identifying slip zones and determining their widths.From the VR measurement on an oriented specimen containing the slip surface of the Wenchuan earthquake from the Shenxigou outcrop,we observed anomalous high VR values in two black-colored slip zones of about 2mm in width near the slip surface.The numerical calculation shows that the maximum temperature rise on the fault plane near Shenxigou was probably less than 162℃ during the Wenchuan earthquake,which means the dynamic fault strength was quite low.These estimations are roughly in accord with the results from the high-velocity frictional experiments. 相似文献
9.
Direct observation of frictional contacts: New insights for state-dependent properties 总被引：9，自引：0，他引：9
Rocks and many other materials display a rather complicated, but characteristic, dependence of friction on sliding history. These effects are well-described by empirical rate- and state-dependent constitutive formulations which have been utilized for analysis of fault slip and earthquake processes. We present a procedure for direct quantitative microscopic observation of frictional contacts during slip. The observations reveal that frictional state dependence represents an increase of contact area with contact age. Transient changes of sliding resistance correlate with changes in contact area and arise from shifts of contact population age. Displacement-dependent replacement of contact populations is shown to cause the diagnostic evolution of friction over a characteristic sliding distance that occurs whenever slip begins or sliding conditions change. 相似文献
10.
《Soil Dynamics and Earthquake Engineering》2012,33(1):152-158
The non-linear dynamic response of the rigid block is linearized by means of a friction model that implicitly considers block response through an experimental parameter obtained from shaking table experiments. In view of the great difficulty in carrying out shaking table experiments, in this technical note some recommendations to estimate friction model parameters are given. The selection of parameters considers the sliding response mode of the block–plane-excitation system: stick–slip or continuous sliding. Once all the friction parameters and block response mode were estimated, a methodology was proposed to compute rigid block dynamic response. The numerical results were then compared to actual experimental data for a rigid block sliding on a geotextile–wood interface, along an inclined plane subjected to base harmonic acceleration. Experiments were carried out for both the stick–slip and the continuous sliding modes. Computed and measured responses for both cases showed good agreement, thus indicating that the methodology developed in this research is adequate to capture the physics (of non-linear nature) of rigid blocks sliding on frictional interfaces subjected to complex harmonic loading. The findings encourage the extension of the linearization technique to the more general seismic loading case. 相似文献
11.
岩石磁化率特征可以帮助判断岩石的形成环境,对地震过程中滑动摩擦伴随高温的物理-化学变化具有显著反应.本研究以钻穿龙门山中段构造带的汶川地震断裂科学钻探2号孔(WFSD-2)岩心为研究对象,使用Bartington MS2K磁化率仪对500~2283.56 m深度的岩心进行高分辨率无损磁化率测试,并结合岩性特征和显微结构探讨了龙门山构造带主要岩石单元的磁化率特征及其地震断裂活动的磁学响应.磁化率测试结果表明,由花岗岩和火山碎屑岩组成的彭灌杂岩体的磁化率值(数十到数千个10~(-6)SI)普遍高于上三叠统须家河组沉积岩的磁化率值(数个到数十个10~(-6)SI).从WFSD-2岩性分布来看,彭灌杂岩上下出露四段,其磁化率值特征反映它们属于不同的岩石单元,它们与下伏须家河组地层呈断层接触,构成叠瓦状构造,指示了龙门山构造带具有强烈的地壳缩短作用.断裂带中处于滑动带的断层泥和假玄武玻璃具有高磁化率特征,而断层角砾岩和碎裂岩不具有高磁化率值特征,表明断层岩磁化率增高的原因可能主要与地震断裂滑动摩擦过程中高温作用下发生的磁性矿物转换有关,断层岩中高磁化率异常可作为大地震活动的证据.WFSD-2岩心中的映秀—北川断裂带(600~960 m)可识别出约80条高磁化率异常的断层岩带,揭示映秀—北川断裂带是一条长期活动的断裂带,龙门山构造带形成演化过程中伴随着大地震活动. 相似文献
12.
Ya-Ju Hsu Jean-Philippe Avouac Shui-Beih Yu Chien-Hsin Chang Yih-Min Wu Jochen Woessner 《Pure and Applied Geophysics》2009,166(10-11):1853-1884
We use preseismic, coseismic, and postseismic GPS data of the 1999 Chi-Chi earthquake to infer spatio-temporal variation of fault slip and frictional behavior on the Chelungpu fault. The geodetic data shows that coseismic slip during the Chi-Chi earthquake occurred within a patch that was locked in the period preceding the earthquake, and that afterslip occurred dominantly downdip from the ruptured area. To first-order, the observed pattern and the temporal evolution of afterslip is consistent with models of the seismic cycle based on rate-and-state friction. Comparison with the distribution of temperature on the fault derived from thermo-kinematic modeling shows that aseismic slip becomes dominant where temperature is estimated to exceed 200° at depth. This inference is consistent with the temperature induced transition from velocity-weakening to velocity-strengthening friction that is observed in laboratory experiments on quartzo-feldspathic rocks. The time evolution of afterslip is consistent with afterslip being governed by velocity-strengthening frictional sliding. The dependency of friction, μ, on the sliding velocity, V, is estimated to be ${{\partial \mu }/{\partial \, {\rm ln}\, V}} = 8 \times 10^{ - 3}$ . We report an azimuthal difference of about 10–20° between preseismic and postseismic GPS velocities, which we interpret to reflect the very low shear stress on the creeping portion of the décollement beneath the Central Range, of the order of 1–3 MPa, implying a very low friction of about 0.01. This study highlights the importance of temperature and pore pressure in determining fault frictional sliding. 相似文献
13.
在与主压应力方向斜交的断层上,正应力与剪应力之间存在线性相关关系,以此为基础导出了小扰动条件下决定稳定性的临界刚度与滑动速率的关系。由于这一关系具有临界刚度随滑动速率增加而减小的特点,因此速率增加可能导致周期性粘滑向稳定滑动转化,而速率减小可能使本来稳定的滑动转化为周期性粘滑过程。在这种斜交断层中,速率增加虽然可能抑制周期性粘滑,但是稳滑时超过一定限度的速率增加会导致一次性不稳定滑动。三轴摩擦实验提供了关于粘滑与稳滑可相互转化的支持证据 相似文献
14.
采用断层位错模式,考虑了具有一定宽度的断层在其粘滑过程中,断层摩擦应力和滑动速度随粘滑过程的变化情况,由此计算了粘滑所产生的摩擦增温,并将结果与不考虑摩擦应力变化、不考虑滑动速度变化或忽略断层宽度时的情况作了比较。结果表明:断层滑动时,摩擦应力和滑动速度随时间的改变及断层的宽度将对断层摩擦增温产生较大影响。由于岩石中孔隙和孔隙流体的存在,摩擦应力在断层粘滑过程中有较大变化。取断层滑动速度为Brune 震源时间函数形式,考虑摩擦应力的变化及一定的断层宽度,计算得到的摩擦增温值较以往的计算结果偏小。这个结论对测定断层活动年代的热释光(TL)和电子自旋共振(ESR) 法具有一定的理论指导意义 相似文献
15.
鄂尔多斯块体周缘历史上多次发生大地震，同时该地区人口稠密，城市群集中，有必要分析该地区未来30年的大地震危险性，为该地区的应急备灾工作提供参考.本文利用块体周缘活动断层的滑动速率、历史地震古地震等资料，建立了考虑大地震发生率的时间非平稳性质和大地震危险性近断层分布特征的地震危险性模型.计算了块体周缘未来30年Ⅷ度地震动的超越概率分布图，并同《中国地震动参数区划图》的地震危险性模型进行了比较.本文研究认为，由断层滑动速率估算的断层地震活动性与基于地震目录统计的地震活动性总体差别不大，但断层源的地震危险性在沿断层破裂面地区增大明显.结果认为，鄂尔多斯块体周缘未来30年地震危险性最高的地区在块体西南缘，六盘山东麓断裂和会宁—义岗断裂及周边地区是未来30年地震危险性较高的地区. 相似文献
16.
James R. Rice 《Pure and Applied Geophysics》1983,121(3):443-475
Constitutive relations for fault slip are described and adopted as a basis for analyzing slip motion and its instability in
the form of earthquakes on crustal faults. The constitutive relations discussed include simple rate-independent slip-weakening
models, in which shear strength degrades with ongoing slip to a residual frictional strength, and also more realistic but
as yet less extensively applied slip-rate and surface-state-dependent relations. For the latter the state of the surface is
characterized by one or more variables that evolve with ongoing slip, seeking values consistent with the current slip rate.
Models of crustal faults range from simple, single-degree-of-freedom spring-slider systems to more complex continuous systems
that incorporate nonuniform slip and locked patches on faults of depth-dependent constitutive properties within elastic lithospheric
plates that may be coupled to a viscoelastic asthenosphere.
Most progress for the rate and state-dependent constitutive relations is at present limited to single-degree-of-freedom systems.
Results for stable and unstable slip with the various constitutive models are summarized. Instability conditions are compared
for spatially uniform versus nonuniform slip, including the elastic — brittle crack limit of the nonuniform mode. Inferences
of constitutive and fracture parameters are discussed, based on earthquake data for large ruptures that begin with slip at
depth, concentrating stress on locked regions within a brittle upper crust. Results of nonlinear stability theory, including
regimes of complex sustained stress and slip rate oscillations, are outlined for rate and state-dependent constitutive relations,
and the manner in which these allow phenomena like time-dependent failure, restrengthening in nearly stationary contact, and
weakening in rapidly accelerated slip, is discussed. 相似文献
17.
Earthquake aftereffects and triggered seismic phenomena 总被引：5，自引：0，他引：5
18.
Richard H. Sibson 《Pure and Applied Geophysics》1986,124(1-2):159-175
Surface-rupture patterns and aftershock distributions accompanying moderate to large shallow earthquakes reveal a residual brittle infrastructure for established crustal fault zones, the complexity of which is likely to be largely scale-invariant. In relation to such an infrastructure, continued displacement along a particular master fault may involve three dominant mechanical processes of rock brecciation: (a)attrition brecciation, from progressive frictional wear along principal slip surfaces during both seismic and aseismic sliding, (b)distributed crush brecciation, involving microfracturing over broad regions when slip on the principal slip surfaces is impeded by antidilational jogs or other obstructions, and (c)implosion brecciation, associated with the sudden creation of void space and fluid-pressure differentials at dilational fault jogs during earthquake rupture propagation. These last, high-dilation breccias are particularly favorable sites for hydrothermal mineral deposition, forming transitory low-pressure channels for the rapid passage of hydrothermal fluids. Long-lived fault zones often contain an intermingling of breccias derived from all three processes. 相似文献
19.
Possible Mechanism of Precursory Seismic Quiescence: Regional Stress Relaxation due to Preseismic Sliding 总被引：3，自引：0，他引：3
—We propose a new model to physically explain the seismic quiescence precursory to a large interplate earthquake. A numerical simulation is performed to quantitatively examine possible stress changes prior to a great interplate earthquake in a subduction zone. In the present study, the frictional force following a laboratory-derived friction law, in which the friction coefficient is dependent on slip rate and slip history, is assumed to act on a dip-slip fault plane of infinite width in a uniform elastic half-space. The values of friction parameters are determined so that the result of numerical simulation may explain some properties of great interplate earthquakes in subduction zones, such as the recurrence interval and the seismic coupling coefficient. The result of simulation reveals that significant quasi-stable sliding occurs prior to a great earthquake and, accordingly, stresses are changed on and around the plate boundary. In a relatively wide area of the overriding continental plate, the compres sional horizontal-stress perpendicular to the trench axis is decreased for a few years before the occurrence of a great earthquake. This decrease in regional compressional stress may account for the appearance of seismic quiescence prior to a great interplate earthquake. 相似文献
20.
R. Kourkoulis I. AnastasopoulosF. Gelagoti G. Gazetas 《Soil Dynamics and Earthquake Engineering》2010
This paper studies the combined effects of earthquake-triggered landslides and ground shaking on foundation−structure systems founded near slope crests. Plane-strain nonlinear finite element dynamic analyses are performed. The soil constitutive model is calibrated against published data to simulate the (post-peak) softening behavior of soil during a seismic event and under the action of gravitational forces. The plastic shear zones and the yield accelerations obtained from our dynamic analyses are shown to be consistent with the slip surfaces and the seismic coefficients obtained by classical pseudostatic limiting equilibrium and limit analysis methods. The foundation and frame columns and beams are modeled as flexural beam elements, while the possibility of sliding and detachment (separation) between the foundation and the underlying soil is considered through the use of special frictional gap elements. The effects of foundation type (isolated footings versus a rigid raft) on the position of the sliding surface, on the foundation total and differential displacements, and on the distress of the foundation slab and superstructure columns, are explored parametrically. It is shown that a frame structure founded on a properly designed raft could survive the combined effects of slope failure and ground shaking, even if the latter is the result of a strong base excitation amplified by the soil layer and slope topography. 相似文献