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通过对天山北麓 190 6年玛纳斯 7 7级地震区的浅层地震探测资料、石油地震反射剖面、二维电性结构剖面、深地震反射剖面的研究 ,发现玛纳斯地震区多层次活动构造系统的根带 ,它通过脆 -韧转换带与天山活动构造块体内上地壳中的低速、高导层连为一体。低速、高导层可能是天山地壳内正在活动的韧性剪切带 ,而齐古逆断裂 -褶皱带下的脆 -韧转换带是连接深部活动韧性剪切带与地壳浅部脆性破裂的枢纽 ,也是现今孕育和发生大地震的重要构造部位。 190 6年玛纳斯地震发生在脆韧转换带的底部 ,地震区的活动逆断裂和褶皱只是部分记录了深部韧性剪切带活动的信息 相似文献
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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
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A two-dimensional model for stress accumulation and earthquake instability associated with strike-slip faults is considered. The model consists of an elastic lithosphere overlying a viscous asthenosphere, and a fault of finite width with an upper brittle zone having an elastoplastic response and a lower ductile zone having an elastoviscoplastic response. For the brittle, or seismic, zone the behavior of the fault material is assumed to be governed by a relation which involves strain hardening followed by a softening regime, with strength increasing with depth. For the fault material in the ductile, or aseismic, section, the viscous effect is included through use of a nonlinear creep law, and the strength is assumed to decrease with depth. Hence, because of the lesser strength and the viscous effect, continuous flow occurs at great depths, causing stress accumulation at the upper portion of the fault and leading to failure at the bottom of the brittle zone. The failure is initially due to localized strain softening but, with further flow, the material above the softened zone reaches its maximum strength and begins to soften. This process accelerates and may result in an unstable upward rupture propagation.Relations are developed for the history of deformation within the lithosphere, specifically for the velocity of particles within the fault and at the ground surface. The boundary-element method is used for a quantitative study, and numerical results are obtained and compared with the recorded surface deformation of the San Andreas fault. The effects of geometry and material properties on instability, on the history of the surface deformation, and on the earthquake recurrence time are studied. The results are presented in terms of variations of ground-surface shear strain and shear strain rate, and velocity of points within the fault at various times during the earthquake cycle.It is found that the location of rupture initiation, the possibility of a sudden rupture as opposed to stable creep, and also the ground deformation pattern and its history, all critically depend on the mechanical response of the material within the fault zone, especially that of the brittle section. Shorter earthquake recurrence times are obtained for shallower brittle zones and for a stiffer lithosphere. Lower viscosities of the aseismic zone and the absence of asthenospheric coupling tend to suppress instability and promote stable creep. The model results thus suggest that the overall viscosity of the ductile creeping zone must exceed a minimum value for a sudden upward propagating rupture to take place within the seismic section. 相似文献
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Field studies and seismic data show that semi-brittle flow of fault rocks probably is the dominant deformation mechanism at the base of the seismogenic zone at the so-called frictional-plastic transition. As the bottom of seismogenic fault, the dynamic characteristics of the frictional-plastic transition zone and plastic zone are very important for the seismogenic fault during seismic cycles. Granite is the major composition of the crust in the brittle-plastic transition zone. Compared to calcite, quartz, plagioclase, pyroxene and olivine, the rheologic data of K-feldspar is scarce. Previous deformation studies of granite performed on a quartz-plagioclase aggregate revealed that the deformation strength of granite was similar with quartz. In the brittle-plastic transition zone, the deformation characteristics of granite are very complex, temperature of brittle-plastic transition of quartz is much lower than that of feldspar under both natural deformation condition and lab deformation condition. In the mylonite deformed under the middle crust deformation condition, quartz grains are elongated or fine-grained via dislocation creep, dynamic recrystallization and superplastic flow, plagioclase grains are fine-grained by bugling recrystallization, K-feldspar are fine-grained by micro-fractures. Recently, both field and experimental studies presented that the strength of K-feldspar is much higher than that of quartz and plagioclase. The same deformation mechanism of K-feldspar and plagioclase occurred under different temperature and pressure conditions, these conditions of K-feldspar are higher than plagioclase. The strength of granite is similar to feldspar while it contains a high content of K-feldspar. High shear strain experiment studies reveal that granite is deformed by local ductile shear zones in the brittle-plastic transition zone. In the ductile shear zone, K-feldspar is brittle fractured, plagioclase are bugling and sub-grain rotation re-crystallized, and quartz grains are plastic elongated. These local shear zones are altered to local slip-zones with strain increasing. Abundances of K-feldspar, plagioclase and mica are higher in the slip-zones than that in other portions of the samples (K-feldspar is the highest), and abundance of quartz is decreased. Amorphous material is easily formed by shear strain acting on brittle fine-grained K-feldspar and re-crystallized mica and plagioclase. Ductile shear zone is the major deformation mechanism of fault zones in the brittle-plastic transition zone. There is a model of a fault failed by bearing constant shear strain in the transition zone:local shear zones are formed along the fractured K-feldspar grains; plagioclase and quartz are fine-grained by recrystallization, K-feldspar is crushed into fine grains, these small grains and mica grains partially change to amorphous material, local slip-zones are generated by these small grains and the amorphous materials; then, the fault should be failed via two ways, 1)the local slip-zones contact to a throughout slip-zone in the center of the fault zone, the fault is failed along this slip-zone, and 2)the local slip-zones lead to bigger mineral grains that are in contact with each other, stress is concentrated between these big grains, the fault is failed by these big grains that are fractured. Thus, the real deformation character of the granite can't be revealed by studies performing on a quartz-plagioclase aggregate. This paper reports the different deformation characters between K-feldspar, plagioclase and quartz under the same pressure and temperature condition based on previous studies. Then, we discuss a mode of instability of a fault zone in the brittle-plastic transition zone. It is still unclear that how many contents of weak mineral phase(or strong mineral phase)will control the strength of a three-mineral-phase granite. Rheological character of K-feldspar is very important for study of the deformation characteristic of the granitic rocks. 相似文献
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Fabric development in brittle-to-ductile shear zones 总被引：3，自引：0，他引：3
Carol Simpson 《Pure and Applied Geophysics》1986,124(1-2):269-288
Brittle-to-ductile shear zones from two separate geological settings are shown to have nucleated on zones of predominantly brittle deformation. The shear zones are not simply foliated cataclasites, since they contain abundant evidence of dynamic recrystallization of constituent minerals. A small quartz diorite lens in the Borrego Springs shear zone, southern California, contains centimeter-scale cataclasite zones that exhibit a gradual transition into foliated rock. Alteration of magnesiohornblende to actinolite, feldspar to white mica plus quartz, and biotite to chlorite, produced elongate minerals that define the foliation. During the later stages of deformation, intracrystalline slip and dynamic recrystallization of quartz and feldspar were important deformation mechanisms.The widespread occurrence of mineralized dilatant cracks predated the development of meter-to-decimeter-scale ductile shear zones in the Striped Rock granite, southern Virginia. Again, important deformation mechanisms in the final stages of deformation were intracrystalline slip and dynamic recrystallization of quartz.In both field areas the role of fluids has been important from the onset of brittle deformation. Fluids may have enhanced early fracturing in addition to causing the alteration and hydrolytic weakening of host rock minerals and the introduction of new mineral species. Each of these processes is thought to have contributed to the later localization of crystal plastic deformation in the rocks. 相似文献
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内蒙古大青山地区的临河-集宁断裂带是华北板块北缘的一条重要断裂带。它主要由韧性剪切带、韧脆性剪切带和推覆构造等构成。推覆构造自南向北可分为叠瓦逆冲推覆构造带、紧闭褶皱-逆冲断层变形带、宽缓褶皱一断层转折褶皱带、滑脱褶皱一断层传播褶皱带等4个变形带。断裂带从韧性到脆性表示了其出露深度不同。并有由南到北活动强度逐渐减弱的趋势。该区主要分布有以金为主的多金属矿床和以煤、大理岩为主的非金属矿床。区内金多金属矿床多与韧性剪切带有关,断裂构造为金属矿床的形成提供了空间,也是成矿物质的通道。研究指出了该地区的找矿前景与方向。 相似文献
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Abstract The fractality of fault zones of thickness T for the 248-m-long core from a borehole penetrating the northern segment of the seismic Chelungpu Fault, Taiwan, was analyzed. The frequency curve of T shows that the fractal dimension is normal when T is smaller than a characteristic thickness T c , and it becomes abnormally large when T exceeds T c . The fractal dimensions of size and spatial distributions of T increase as the mean distribution density of T increases, which is inconsistent with the evolution laws for ordinary brittle faults. This discrepancy implies that the thickening rate of T when T is more than T c is not constant, but a decreasing function of fault displacement. The slow thickening rate is related to the elastohydrodynamic lubrication which was effective on the fault when T exceeds T c . This slip instability mechanism can explain the large, fast and smooth slip on the northern segment of the Chelungpu Fault during the 1999 Chi-Chi earthquake. 相似文献
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断层泥的再生显微结构特征及其地震地质意义 总被引：3，自引：1，他引：3
三轴剪切摩擦实验后的断层泥与天然断层泥的再生显微结构特征研究表明，断层泥的显微结构特征与断层滑动方式之间有一定的关系，稳滑使断层泥变形均匀，产生低角度剪切（＜１４°）、布丁构造和颗粒碎裂流动。粘滑使断层泥局部发生强烈变形、高角度剪切（＞１４°）和碎粒出现随机裂纹等。断层泥的再生显微结构特征可用作鉴别古地震的存在 相似文献
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Norman H. Sleep 《Pure and Applied Geophysics》1994,143(1-3):41-60
A conceptually simple process which establishes a steady grain size distribution is envisioned to control the ductile creep properties of fault zones that mainly slip by frictional processes. Fracture during earthquakes and aseismic frictional creep tend to reduce grain size. However, sufficiently small grains tend to dissolve so that larger grains grow at their expense, a process called Ostwald ripening. A dynamic stedy state is reached where grain size reduction by fracture is balanced by grain growth from Ostwald ripening. The ductile creep mechanism within fault zones in hard rock is probably pressure solution where the rate is limited by diffusion along load-bearing grain-grain contacts. The diffusion paths that limit Ostwald repening are to a considerable extent the same as those for pressure solution. Active Ostwald ripening thus implies conditions suitable for ductile creep. An analytic theory allows estimation of the steady-state mean grain size and the viscosity for creep implied by this dynamic steady state from material properties and from the width, shear traction, and long-term slip velocity of the fault zone. Numerical models were formulated to compute the steady state grain size distribution. The results indicate that ductile creep, as suggested in the companion paper, is a plausible mechanism for transiently increasing fluid pressure within mostly sealed fault zones so that frictional failure occurs at relatively low shear tractions, 10 MPa. The relevant material properties are too poorly known, however, for the steady state theory (or its extension to a fault that slips in infrequent large earthquakes) to have much predictive value without additional laboratory experiments and studies of exhumed faults. 相似文献
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We present a thermodynamically-based formulation for mechanical modeling of faulting processes in the seismogenic brittle crust using a continuum damage–breakage rheology. The model combines previous results of a continuum damage framework for brittle solids with continuum breakage mechanics for granular flow. The formulation accounts for the density of distributed cracking and other internal flaws in damaged rocks with a scalar damage parameter, and addresses the grain size distribution of a granular phase in a failure slip zone with a breakage parameter. The stress–strain relation and kinetics of the damage and breakage processes are governed by the total energy function of the system, which combines the energy of the damaged solid with the energy of the granular material. A dynamic brittle instability is associated with a critical level of damage in the solid, leading to loss of convexity of the solid energy function and transition to a granular phase associated with lower energy level. A non-local formulation provides an intrinsic length scale associated with the internal damage structure, which leads to a finite length scale for damage localization that eliminates the unrealistic singular localization of local models. Shear heating during deformation can lead to a secondary finite-width internal localization. The formulation provides a framework for studying multiple aspects of brittle deformation, including potential feedback between evolving elastic moduli and properties of the slip localization zone and subsequent rupture behavior. The model has a more general transition from slow deformation to dynamic rupture than that associated with frictional sliding on a single pre-existing failure zone, and gives time and length scales for the onset of the dynamic fracturing process. Several features including the existence of finite localization width and transition from slow to rapid dynamic slip are illustrated using numerical simulations. A configuration having an existing narrow slip zone with localized damage produces for appropriate loading conditions an overall cyclic stick–slip motion. The simulated frictional response includes transitions from friction coefficient of ~0.7 at low slip velocity to dynamic friction below 0.4 at slip rates above ~0.1 m/s, followed by rapidly increasing friction for slip rates above ~1 m/s, consistent with laboratory observations. 相似文献
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Koichiro Fujimoto Hidemi Tanaka Takayuki Higuchi Naoto Tomida Tomoyuki Ohtani Hisao Ito 《Island Arc》2001,10(3-4):401-410
Abstract Mineralogical and geochemical studies on the fault rocks from the Nojima–Hirabayashi borehole, south-west Japan, are performed to clarify the alteration and mass transfer in the Nojima Fault Zone at shallow depths. A complete sequence from the hornblende–biotite granodiorite protolith to the fault core can be observed without serious disorganization by surface weathering. The parts deeper than 426.2 m are in the fault zone where rocks have suffered fault-related deformation and alteration. Characteristic alteration minerals in the fault zone are smectite, zeolites (laumontite, stilbite), and carbonate minerals (calcite and siderite). It is inferred that laumontite veins formed at temperatures higher than approximately 100°C during the fault activity. A reverse component in the movement of the Nojima Fault influences the distribution of zeolites. Zeolite is the main sealing mineral in relatively deep parts, whereas carbonate is the main sealing mineral at shallower depths. Several shear zones are recognized in the fault zone. Intense alteration is localized in the gouge zones. Rock chemistry changes in a different manner between different shear zones in the fault zone. The main shear zone (MSZ), which corresponds to the core of the Nojima Fault, shows increased concentration of most elements except Si, Al, Na, and K. However, a lower shear zone (LSZ-2), which is characterized by intense alteration rather than cataclastic deformation, shows a decreased concentration of most elements including Ti and Zr. A simple volume change analysis based on Ti and Zr immobility, commonly used to examine the changes in fault rock chemistry, cannot account fully for the different behaviors of Ti and Zr among the two gouge zones. 相似文献
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Steven A. F. Smith Andrea Billi Giulio Di Toro Richard Spiess 《Pure and Applied Geophysics》2011,168(12):2365-2393
Earthquakes in central Italy, and in other areas worldwide, often nucleate within and rupture through carbonates in the upper crust. During individual earthquake ruptures, most fault displacement is thought to be accommodated by thin principal slip zones. This study presents detailed microstructural observations of the slip zones of the seismically active Tre Monti normal fault zone. All of the slip zones cut limestone, and geological constraints indicate exhumation from <2?km depth, where ambient temperatures are ?100°C. Scanning electron microscope observations suggest that the slip zones are composed of 100% calcite. The slip zones of secondary faults in the damage zone contain protocataclastic and cataclastic fabrics that are cross-cut by systematic fracture networks and stylolite dissolution surfaces. The slip zone of the principal fault has much more microstructural complexity, and contains a 2?C10?mm thick ultracataclasite that lies immediately beneath the principal slip surface. The ultracataclasite itself is internally zoned; 200?C300???m-thick ultracataclastic sub-layers record extreme localization of slip. Syn-tectonic calcite vein networks spatially associated with the sub-layers suggest fluid involvement in faulting. The ultracataclastic sub-layers preserve compelling microstructural evidence of fluidization, and also contain peculiar rounded grains consisting of a central (often angular) clast wrapped by a laminated outer cortex of ultra-fine-grained calcite. These ??clast-cortex grains?? closely resemble those produced during layer fluidization in other settings, including the basal detachments of catastrophic landslides and saturated high-velocity friction experiments on clay-bearing gouges. An overprinting foliation is present in the slip zone of the principal fault, and electron backscatter diffraction analyses indicate the presence of a weak calcite crystallographic preferred orientation (CPO) in the fine-grained matrix. The calcite c-axes are systematically inclined in the direction of shear. We suggest that fluidization of ultracataclastic sub-layers and formation of clast-cortex grains within the principal slip zone occurred at high strain rates during propagation of seismic ruptures whereas development of an overprinting CPO occurred by intergranular pressure solution during post-seismic creep. Further work is required to document the range of microstructures in localized slip zones that cross-cut different lithologies, and to compare natural slip zone microstructures with those produced in controlled deformation experiments. 相似文献
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GPS monitoring of temporal deformation of the Xianshuihe fault 总被引：3，自引：0，他引：3
Min Wang ZhengKang Shen WeiJun Gan Hua Liao TieMing Li JinWei Ren XueJun Qiao QingLiang Wang YongLin Yang Kato Teruyuki Peng Li 《中国科学D辑(英文版)》2008,51(9):1259-1266
Highly precise (σ ~1 mm) temporal deformation measurements are taken across the Xianshuihe fault from two pairs of continuous GPS stations straddling the fault. Baseline vector changes of the two pairs of stations show clearly the difference in deformation behavior between the Qianning and Daofu segments of the fault: the former deforms steadily, and the latter deforms with a strong transient component. The transient deformation across the Daofu segment is possibly related to its irregular geometry, where the fault splits into two branches, that is, the east and west branches. An attempt is made to interpret the baseline vector changes using a kinematic fault model composed of a brittle layer in the upper crust, a ductile layer in the lower crust, and a transition zone in between. The slip in the transition zone of the south segment of the Xianshuihe fault is steady. The slips in the transition zones of the north and Daofu segments of the Xianshuihe fault, however, are not steady, and the average slip rates there are higher than that of the south segment. The difference in deformation behavior is probably associated with the rheological properties of the fault interface, suggesting that the overall fault strength of the south segment is greater than those of the north and Daofu segments, corresponding to longer earthquake recurrence time. 相似文献
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NI JinLong LIU JunLai TANG XiaoLing ZHAO ChunQiang & ZENG QingDong 《中国科学:地球科学(英文版)》2014,57(4):600-613
The combination of field surveys with analysis of microstructure of tectonite and Electron Backscatter Diffraction (EBSD) on quartz fabric indicated that three periods of ductile shear events developed in the Paishanlou gold deposits and the E-W and NE-striking ductile shear zones were formed during each event. The E-W-striking ductile shear zone, accompanied by compressional and dextral shear slip, was shear-cut by the NE-striking shear zones, accompanied by compressional-sinistral shear slip and sinistral-normal shear slip, successively. An E-W-striking ductile shear zone developed at a deeper tectonic level and at middle- to high-temperatures, accompanied by abundant microstructures, including microlayering between a polycrystal quartz belt and mica, and quartz deformation was depended on cylinder (10-10) 〈a〉 or 〈c〉 glide. The development of an E-W-striking shear zone can be seen as a tectonic pattern in the region of the Paishanlou gold deposits of the collision between the Mongolian tectonic belt and the North Archean Craton from Suolun to the Linxi suture zone during the Indosinian. The NE-striking ductile shear zone developed approximately 160 Ma during the early Yianshanian at middle to shallow tectonic levels and at middle- to low-temperatures, accompanied by typical microstructures, including polycrystal quartz aggregation and quartz subgrain rotation recrystallization, etc., and quartz deformation was depended on prismatic (1011) 〈a〉 glide. The last ductile shear event around the NE-striking shear zone developed at low temperatures and shallow tectonic levels, yielding to a pre-existing NE-striking shear zone, accompanied by abundant microstructures, including low-temperature quartz grain boundary migration and bulging recrystallization. The last ductile shear movement may be related to lithosphere thinning and the destruction of the North China Craton from approximately 130-120 Ma, and this shear event resulted directly in the mineralization in the Paishanlou region. 相似文献
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C. Doglioni S. Barba E. Carminati F. Riguzzi 《Physics of the Earth and Planetary Interiors》2011,184(3-4):160-171
We model a fault cross-cutting the brittle upper crust and the ductile lower crust. In the brittle layer the fault is assumed to have stick–slip behaviour, whereas the lower ductile crust is inferred to deform in a steady-state shear. Therefore, the brittle–ductile transition (BDT) separates two layers with different strain rates and structural styles. This contrasting behaviour determines a stress gradient at the BDT that is eventually dissipated during the earthquake. During the interseismic period, along a normal fault it should form a dilated hinge at and above the BDT. Conversely, an over-compressed volume should rather develop above a thrust plane at the BDT. On a normal fault the earthquake is associated with the coseismic closure of the dilated fractures generated in the stretched hangingwall during the interseismic period. In addition to the shear stress overcoming the friction of the fault, the brittle fault moves when the weight of the hangingwall exceeds the strength of the dilated band above the BDT. On a thrust fault, the seismic event is instead associated with the sudden dilation of the previously over-compressed volume in the hangingwall above the BDT, a mechanism requiring much more energy because it acts against gravity. In both cases, the deeper the BDT, the larger the involved volume, and the bigger the related magnitude.We tested two scenarios with two examples from L’Aquila 2009 (Italy) and Chi-Chi 1999 (Taiwan) events. GPS data, energy dissipation and strain rate analysis support these contrasting evolutions. Our model also predicts, consistently with data, that the interseismic strain rate is lower along the fault segment more prone to seismic activation. 相似文献