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1.
The particle size distributions of fault gouge from the San Andreas, the San Gabriel, and the Lopez Canyon faults in Southern California were measured using sieving and Coulter-Counter techniques over a range of particle sizes from 2 m to 16 mm. The distributions were found to be power law (fractal) for the smaller fragments and log-normal by mass for sizes near and above the peak size. The apparent fractal dimensionD of the smaller particles in gouge samples from the San Andreas fault, the San Gabriel fault and the Lopez Canyon gouge were 2.4–3.6, 2.6–2.9 and 2.4–3.0, respectively. The averageD for the Lopez Canyon gouge was 2.7±0.2, which is in agreement with earlier studies of this gouge using planar 2-D sections. The fractal dimension of the finer fragments from all three faults is observed to be correlated with the peak fragment size, with finer gouges tending to have a largerD. A computer automaton is used to show that this observation may be explained as resulting from a fragmentation process which has a grinding limit at which particle reduction stops. 相似文献
2.
在不同的压力、温度和孔隙压力下进行了含四种不同断层泥标本的强度试验。碎屑型断层泥对压力很敏感,对温度无反应,对孔隙压力的反应符合有效应力律。粘土类断层泥则对温度和孔隙压力有明显响应。这些力学性质的差别反映了具体变形机制的差别 相似文献
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4.
The kinematics of gouge deformation 总被引：13，自引：0，他引：13
The methods and first results of a new approach to examining fault gouge are described. Samples of undisturbed fault gouge from the exhumed Lopez fault zone in the San Gabriel Mountains, California were impregnated with low viscosity epoxy resin and sectioned to produce microscope slides. The slides were photographed using optical and electron microscopy with magnifications ranging in factors of 2 from 12.5 to 1600. At all scales, the particles appeared angular with planar faces, suggesting tensile failure. No shear zones were discernable. The particle size distribution was studied. At each magnification the particles were sorted by diameter into four classes, differing in mean diameter by factors of 2. The numbers in each class were then scaled by the characteristic class dimension. The process revealed a remarkable degree of self-similarity. Over the range examined, the fractal dimension was within 5% of 2.60.On the basis of the observations, a new model for the mechanical processes that generate gouge is offered. It is argued that self-similarity results from repeated tensile splitting of grains. Unlike earlier models that consider splitting probability to be either independent of particle size or due to the preexisting distribution of defects, we propose that failure probability depends largely on the relative size of nearest neighbors. If nearest neighbors of the same size are preferentially broken, any initial distribution of particles will tend toward a self-similar distribution having a fractal dimension of 2.58.The model allows us to outline a procedure whereby the observed comminution in a fault zone can be related to the shear strain that the zone has accommodated and propose a theoretical frequency magnitude relation for the seismic energy emitted by the fracture process. 相似文献
5.
5.12汶川地震同震地表破裂带在虹口八角-深溪沟一带主要出露于三叠系须家河组的炭质泥岩中,同震断层泥在颜色、结构上与老断层泥和围岩类似。通过开挖探槽,系统采样,采用粉晶X射线衍射定量分析方法,研究了同震地表破裂带的围岩、断层角砾岩、老断层泥和新断层泥的矿物成分特征。同震断层泥的主要成分为石英和黏土矿物,含微量长石和白云石;断层泥的显著特征为高黏土矿物含量,从同震断层泥、老断层泥、角砾岩到围岩黏土矿物含量依次降低,黏土矿物以伊利石和伊蒙混层为主,含微量绿泥石和高岭石,矿物组成明显比地表破裂带北段同震断层泥简单。不同颜色的同震断层泥成分略有不同,黑色断层泥中伊利石含量明显高于白色断层泥;老断层泥中含有方解石和白云石,而同震断层泥不含方解石,只含微量白云石。同震断层泥中伊蒙混层高含量表明,在本次地震错动中有富含K的流体参与。 相似文献
6.
Summary In the northern and central sections of the San Andreas Fault Zone, and along Calaveras and Hayward faults, clay gouges have been found to occur on the surface and at shallow depths.It is consistent with the available geochemical data that such gouges can exist at depths down to 10 km. If extensive gouge materials exist in a fault zone then their properties will determine, to a large extent, the behavior of the fault. From known properties of clays in the presence of water we can infer that, in such cases, the tectonic stress and the stress drops for earthquakes will be low and substantial creep will take place before earthquakes. 相似文献
7.
Detailed observation of the microstructural features of 11 fault gouge and 3 fault breccia samples collected from Tianjingshan-Xiangshan
fault zone has revealed that fault gouge can be classified into 3 types: flow banded granular gouge, foliated gouge and massive
gouge. The determination of the shape preferred orientation (SPO) of survivor grains in fault gouges indicates that the foliated
gouge displays a profound SPO inclined to the shear zone boundary, similar to theP-foliation; flow banded granular gouge displays a SPO parallel to the shear zone boundary, while massive fault gouge and fault
breccia display a random SPO. All these fault gouges fall in different fields of shear rate ternary diagram. 相似文献
8.
Seismic measurements of the internal properties of fault zones 总被引：1，自引：0，他引：1
The internal properties within and adjacent to fault zones are reviewed, principally on the basis of laboratory, borehole, and seismic refraction and reflection data. The deformation of rocks by faulting ranges from intragrain microcracking to severe alteration. Saturated microcracked and mildly fractured rocks do not exhibit a significant reduction in velocity, but, from borehole measurements, densely fractured rocks do show significantly reduced velocities, the amount of reduction generally proportional to the fracture density. Highly fractured rock and thick fault gouge along the creeping portion of the San Andreas fault are evidenced by a pronounced seismic low-velocity zone (LVZ), which is either very thin or absent along locked portions of the fault. Thus there is a correlation between fault slip behavior and seismic velocity structure within the fault zone; high pore pressure within the pronounced LVZ may be conductive to fault creep. Deep seismic reflection data indicate that crustal faults sometimes extend through the entire crust. Models of these data and geologic evidence are consistent with a composition of deep faults consisting of highly foliated, seismically anisotropic mylonites. 相似文献
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10.
Kenta Kobayashi Satoshi Hirano Takashi Arai Ryuji Ikeda Kentaro Omura Hiroyuki Sano Takashi Sawaguchi Hidemi Tanaka Tomoaki Tomita Naoto Tomida Tatsuo Matsuda Akiko Yamazaki 《Island Arc》2001,10(3-4):411-421
Abstract Characteristics of deformation and alteration of the 1140 m deep fracture zone of the Nojima Fault are described based on mesoscopic (to the naked eye) and microscopic (by both optical and scanning electron microscopes) observations of the Hirabayashi National Research Institute for Earth Science and Disaster Prevention (NIED) drill core. Three types of fault rocks; that is, fault breccia, fault gouge and cataclasite, appear in the central part of the fault zone and two types of weakly deformed and/or altered rocks; that is, weakly deformed and altered granodiorite and altered granodiorite, are located in the outside of the central part of the fault zone (damaged zone). Cataclasite appears occasionally in the damaged zone. Six distinct, thin foliated fault gouge zones, which dip to the south-east, appear clearly in the very central part of the fracture zone. Slickenlines plunging to the north-east are observed on the surface of the newest gouge. Based on the observations of XZ thin sections, these slickenlines and the newest gouge have the same kinematics as the 1995 Hyogo-ken Nanbu earthquake (Kobe earthquake), which was dextral-reverse slip. Scanning electron microscopy observations of the freeze-dried fault gouge show that a large amount of void space is maintained locally, which might play an important role as a path for fluid migration and the existence of either heterogeneity of pore fluid pressure or strain localization. 相似文献
11.
James R. O'Neil 《Pure and Applied Geophysics》1984,122(2-4):440-446
Measurements were made of the amounts of D,18O, and H2O+ in fault gouge collected over a depth of 400 m in the San Andreas fault of California. The amounts and isotopic compositions of the pore fluids, also analyzed, suggest that formation waters from adjacent Franciscan rocks have migrated into the gouge and mixed with local meteoric water. Thus the gouge is an open system permeable to fluid flow. This permeability has important implications concerning heat flow along the fault zone.Analyses of the fault gouge itself give information on the amounts, timing, and conditions of formation of the clay minerals.Stable-isotope analyses of materials from fault zones are good indicators of water-rock interactions that bear importantly on processes taking place in seismically active regions. 相似文献
12.
本文对海原断裂的断层泥的各类特征进行了系统的研究,分析了断层泥带内部的小型断裂类型,探讨了断层泥组分的有机地球化学意义。通过对比,确立了石英碎屑表面机械作用成因的电子显微构造特征组合为活断层的判别标志。本文将石英碎屑表面电子显微溶蚀构造分为五类,据此分析了断层活动时期和状态。研究中还发现了断层泥带内部电子显微结构类型,进而分析了断层活动与微结构、粒度分布间的关系。最后还讨论了断层泥形成演化过程以及断层泥对全新世以来断层滑动性能影响及其与地震活动的关系 相似文献
13.
In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge. 相似文献
14.
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
15.
Francis T. Wu 《Pure and Applied Geophysics》1978,116(4-5):655-689
Fault gouges have been observed in the surface outcrops, in shallow excavations, and in deep (300 meters below the surface) tunnels and mines in fault zones. The 2-microns fractions in these fault gouges may compose a few percent to more than fifty percent of the total mass in the outcrops, and the mineralogy of the 2-microns fractions consists of a variety of clays (the common ones are montmorillonite, illite, kaolinite, chlorite, vermiculite and mixed-layer clays) and some quartz, feldspars, etc.Although we cannot yet conclude directly from the studies of gouges that similar gouges exist at depths where many large shallow earthquakes are generated, there is a strong possibility that they do, based on (1) available equilibrium data on various clays — for example, kaolinite has been found to exist at 4 kb and 375°C (±15°C) (Thompson, 1970) and montmorillonite + kaolite has been found to exist at 450°C and 4 kb (Velde, 1969); (2) the compatibility of laboratory velocity data in gouge (Wang
et al., 1977) with those in a model for central California (Healy andPeake, 1975); (3) the capability of clays to undergo sudden earthquake-like displacements (Summers andByerlee, 1977); (4) the petrology of intrafault cataclastic rocks in old fault zones (Kasza, 1977); and (5) the compatibility of gouge mineralogy with the mineralogy of hydrothermal clay deposits.If clay gouges are indeed significant components of the fault zone at depth, then the mechanical properties of clays under confining pressures up to 4 kb are important in the behavior of faults. Very few experiments have been performed under such high pressures. But from the physical makeup of clays, we can infer that (1) the range of possible behavior includes stable sliding with vermiculite and montmorillonite (asByerlee andSummers, 1977, have proven) to stick-slip-like behavior with kaolinite, chlorite, etc.; (2) the absence or presence of water will greatly affect the strengths of gouges — it is possible that water may reduce the strength of gouge to a fairly small value. 相似文献
16.
THE GEOLOGICAL AND ROCK MECHANICAL DISTINCTION EVIDENCE BETWEEN STICK-SLIP AND CREEP IN HOST ROCK SEGMENTS OF FAULT 
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下载免费PDF全文 ZHOU Yong-sheng 《地震地质》2019,41(5):1266-1272
Paleo-seismic and fault activity are hard to distinguish in host rock areas compared with soft sedimentary segments of fault. However, fault frictional experiments could obtain the conditions of stable and unstable slide, as well as the microstructures of fault gouge, which offer some identification marks between stick-slip and creep of fault.
We summarized geological and rock mechanical distinction evidence between stick-slip and creep in host rock segments of fault, and analyzed the physical mechanisms which controlled the behavior of stick-slip and creep. The chemical composition of fault gouge is most important to control stick-slip and creep. Gouge composed by weak minerals, such as clay mineral, has velocity weakening behavior, which causes stable slide of fault. Gouge with rock-forming minerals, such as calcite, quartz, feldspar, pyroxene, has stick-slip behavior under condition of focal depth. To the gouge with same chemical composition, the deformation mechanism controls the frictional slip. It is essential condition to stick slip for brittle fracture companied by dilatation, but creep is controlled by compaction and cataclasis as well as ductile shear with foliation and small fold. However, under fluid conditions, pressure solution which healed the fractures and caused strength recovery of fault, is the original reason of unstable slide, and also resulted in locking of fault with high pore pressure in core of fault zone. Contrast with that, rock-forming minerals altered to phyllosilicates in the gouges by fluid flow through degenerative reaction and hydrolysis reaction, which produced low friction fault and transformations to creep. The creep process progressively developed several wide shear zones including of R, Y, T, P shear plane that comprise gouge zones embedded into wide damage zones, which caused small earthquake distributed along wide fault zones with focal mechanism covered by normal fault, strike-slip fault and reverse fault. However, the stick-slip produced mirror-like slide surfaces with very narrow gouges along R shear plane and Y shear plane, which caused small earthquake distributed along narrow fault zones with single kind of focal mechanism. 相似文献
17.
Three-dimensional P-wave Velocity Structure of the Bear Valley Region of Central California 总被引：1，自引：0，他引：1
—The three-dimensional P-wave velocity structure of the Bear Valley region of central California is determined by applying a circular ray-tracing technique to 1735 P-wave arrivals from 108 locally recorded earthquakes. Comparison of the results obtained from one-dimensional and laterally varying starting models shows that many of the features in the structure determined are fairly insensitive to the choice of the starting model. Velocities associated with the Gabilan granites southwest of the San Andreas Fault are slightly higher than those in the Franciscan formation to the northeast, and these two features are separated in the southern part of the region by a narrow fault zone with very low velocities. In the southeastern part of the region, where the Gabilan granites do not abut the San Andreas Fault, the low velocities of the fault zone cross over to the southwestern side of the fault. They also appear to extend to depths of at least 15km, thus locally reversing the contrast across the San Andreas Fault that prevails farther to the northwest. In the northwestern part of the region, the low velocities of the fault zone split and follow the surface traces of the San Andreas and Calaveras Faults, but do not appear to extend to depths much deeper than about 6km. There also appears to be a well-defined contrast in structure in the middle of the Santa Clara Valley, suggesting the existence of a fault in the basement of the valley that may be a southern extension of the Sargent Fault into this region. Relocated hypocenters beneath the San Andreas Fault cluster in a zone that dips about 80° southwest and intersects the surface trace of the fault in the southern part of region. 相似文献
18.
FRICTIONAL PROPERTIES OF A NATURAL FAULT GOUGE FROM DRILLED CORES IN THE LONGMENSHAN FAULT ZONE CUTTING GRANITIC ROCK 下载免费PDF全文
下载免费PDF全文 In this paper, we report friction experiments performed on natural fault gouge samples embedded in granitic rock from drilled core by a project entitled "the Longmenshan Fault Shallow Drilling(LMFD)". Compared with other natural fault gouge, this yellow-greenish gouge(YGG)is dominantly chlorite-rich. The maximum content of chlorite reaches 47%in the YGG. To understand the frictional properties of the YGG sample, experiments were performed at constant confining pressure of 130MPa, with constant pore pressure of 50MPa and at different temperatures from 25℃ to 150℃. The experiments aim to address the frictional behavior of the YGG under shallow, upper crustal pressure, and temperature conditions. Compared with previous studies of natural gouge, our results show that the YGG is stronger and shows a steady state friction coefficient of 0.47~0.51. Comparison with previous studies of natural gouge with similar content of clay minerals indicates a sequence of strengths of different clay minerals:chlorite > illite > smectite. At temperatures up to 150℃ hence depths up to~8km in the Longmenshan region, the YGG shows stable velocity-strengthening behavior at shallow crustal conditions. Combined with the fact of strong direct velocity effect, i.e., (a-b)/a>0.5, faults cutting the present clastic lithology up to~8km depth in the Longmenshan fault zone(LFZ)are likely to offer stable sliding resistance, damping co-seismic rupture propagating from below at not-too-high slip rates. However, as the fault gouge generally has low permeability, co-seismic weakening through thermal pressurization may occur at high slip rates(>0.05m/s), leading to additional hazards. 相似文献
19.
Comparative microstructures of natural and experimentally produced clay-bearing fault gouges 总被引：2，自引：0，他引：2
Fault rocks formed in phyllosilicate-bearing rocks formed over a wide range of environmental conditions within the Earth's crust are characterised by similar structural and microstructural features. The most striking of these are (a) P foliation, defined by the preferred alignment of phyllosilicates in a plane oblique to the direction of shear and (b) small-scale shear zones either parallel to the shear direction (Y shears) or oblique to the direction of shear but with the opposite sense of obliquity relative to the P foliation (Riedel shears, R1). The minor shear zones have the same sense of displacement as the host shear zone.The occurrence of these and other structures in clay-rich fault gouges from exceptionally well-exposed fault zones in southeastern Spain is described. The pervasive development of these flow structures throughout large volumes of fault gouge permits fault-displacement vectors to be inferred. For the region studied the movement pictures is relatively simple and is superposed on a complex network of variably oriented fault zones.The naturally produced fault-gouge structures are compared with fault gouges produced experimentally by shearing kaolinite-quartz mixtures between intact blocks over a wide range of experimental conditions. Good correspondence between their respective microstructural features was observed.Finally, attention is drawn to the fact that natural clay-bearing fault gouges are the products of deformation accompanied by very low-grade retrogressive metamorphism, and that part of the micro-structure of these rocks may be ascribed to crystallization under stress. Microstructures are described that are from long-duration experimental runs, (5 months at high temperature and in the presence of water) which go some way towards simulating these effects. 相似文献
20.
B. A. Verberne C. J. Spiers A. R. Niemeijer J. H. P. De Bresser D. A. M. De Winter O. Plümper 《Pure and Applied Geophysics》2014,171(10):2617-2640
We report an experimental and microstructural study of the frictional properties of simulated fault gouges prepared from natural limestone (96 % CaCO3) and pure calcite. Our experiments consisted of direct shear tests performed, under dry and wet conditions, at an effective normal stress of 50 MPa, at 18–150 °C and sliding velocities of 0.1–10 μm/s. Wet experiments used a pore water pressure of 10 MPa. Wet gouges typically showed a lower steady-state frictional strength (μ = 0.6) than dry gouges (μ = 0.7–0.8), particularly in the case of the pure calcite samples. All runs showed a transition from stable velocity strengthening to (potentially) unstable velocity weakening slip above 80–100 °C. All recovered samples showed patchy, mirror-like surfaces marking boundary shear planes. Optical study of sections cut normal to the shear plane and parallel to the shear direction showed both boundary and inclined shear bands, characterized by extreme grain comminution and a crystallographic preferred orientation. Cross-sections of boundary shears, cut normal to the shear direction using focused ion beam—SEM, from pure calcite gouges sheared at 18 and 150 °C, revealed dense arrays of rounded, ~0.3 μm-sized particles in the shear band core. Transmission electron microscopy showed that these particles consist of 5–20 nm sized calcite nanocrystals. All samples showed evidence for cataclasis and crystal plasticity. Comparing our results with previous models for gouge friction, we suggest that frictional behaviour was controlled by competition between crystal plastic and granular flow processes active in the shear bands, with water facilitating pressure solution, subcritical cracking and intergranular lubrication. Our data have important implications for the depth of the seismogenic zone in tectonically active limestone terrains. Contrary to recent claims, our data also demonstrate that nanocrystalline mirror-like slip surfaces in calcite(-rich) faults are not necessarily indicative of seismic slip rates. 相似文献