八宝山断层的变形行为与降雨及地下水的关系

利用北京丰台大灰厂观测台站1970——2003年的长期综合观测资料,系统分析了降雨和地下水对北京八宝山断层变形行为的影响. 研究结果表明:当降雨量持续稳定周期性变化,则断层孔隙压也呈稳定周期性变化,断层变形行为也表现出明显的规则周期性变化;当降雨量明显偏低或偏离正常周期性变化,则断层孔隙压周期性消失,断层的变形行为方式也发生改变. 降雨通过改变断层带孔隙压力的变化而影响着八宝山断层的变形行为. 结合该断层已有研究结果,认为降雨和地下水有可能通过改变断层变形行为方式而影响着区域构造应力/应变场的调整. 这一结果将对研究地球浅部流体与固体相互作用提供直接的观测证据.      

Coupled Models of Brittle-plastic Deformation and Fluid Flow: Approaches,Methods, and Application to Mesoproterozoic Mineralisation at Mount Isa,Australia

Rock deformation has an important effect on the spatial distribution and temporal evolution of permeability in the Earth’s crust. Hydromechanical coupling is of fundamental significance to natural fluid–rock interaction in porous and fractured hydrothermal systems, and in the assessment and production of hydrocarbon resources and geothermal energy. Shearing and fracturing of rocks can lead to the creation or destruction of permeability when fractures or faults form, or when existing structures are reactivated. Changes in stress orientation or fluid pressure can drive rock failure and create dilating fault zones that have the potential to focus fluid flow, or to breach seals above overpressured fluid compartments. Here, numerical models of deformation and fluid flow related to Mesoproterozoic copper mineralisation at Mount Isa, Australia, are presented that show how changes in deformation geometry in multiply deformed geological architectures relate to changes in dilation patterns, fluid pathways and flow geometry. Coupled numerical simulations of deformation and fluid flow can be useful tools to better understand structural control on fluid flow in hydrothermal mineral systems.     

Relation of deformation behavior with precipitation and groundwater of the Babaoshan fault in Beijing

Introduction The surface of the Earth is the main location where the fluid strongly interacts with solid, and where the atmosphere, hydrosphere, biosphere, and lithosphere strongly interact. Obviously, fault zones as the channels of fluid (water) flow are the focus area of this strong interaction. Earth-quakes, as the products of tectonic activity, occurred near or on the fault zones, can be regarded as one of the results of this strong interaction. Bolt (1999) pointed out that if there were …     

Fault zone characteristics and scaling properties of the Val d’Agri Fault System (Southern Apennines, Italy)

Systematic in situ analysis of active fault zones in Val d’Agri (southern Italy) suggests that the acquisition of quantitative data on fault-related structural discontinuities is fundamental for (1) discriminating between the latter and older regional features, (2) defining the architecture and related permeability structure of faults, and (3) performing simple statistics in order to evaluate the validity range within which fault characteristics may be considered to be fractals. This type of information can be integrated with regional seismotectonic analysis in order to asses the present-day conditions of deformation characterising the area, and to constrain the possible kinematics of the seismogenic structures controlling earthquake activity in this sector of the southern Apennines. The results of our study are also of interest for modelling earthquake sources, since a knowledge of the permeability structure and scaling properties of a faulted rock volume is potentially relevant for simulating the time and space dependent behaviour of fault zones during a seismic cycle.     

Comparative microstructures of natural and experimentally produced clay-bearing fault gouges

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.     

Petrophysical study of faults in sandstone using petrographic image analysis and X-ray computerized tomography

Petrographic image analysis (PIA) and X-ray computerized tomography (CT) provide local determinations of porosity in sandstone. We have investigated small faults called deformation bands in porous sandstones using these techniques. Because the petrophysical properties of the fault rock vary at a small scale (mm scale), the ability of PIA and CT to determine porosity in small volumes of rock and to map porosity distribution in two and three dimensions is crucial. This information is used to recognize the processes involved in fault development and the different kinds of microstructures associated with dilatancy and compaction. The petrophysical study of fault rock in sandstone permits one to make predictions of the hydraulic properties of a fault and thereby evaluate the sealing or fluid transmitting characteristics of faulted reservoirs and aquifers. The results of this study indicate that faulting in sandstone alters the original porosity and permeability of the host rock: the porosity is reduced by an order of magnitude and the permeability is reduced by one to more than seven orders of magnitude for faults associated with compaction.     

汶川地震科学钻探2号孔(WFSD-2)随钻泥浆氢和汞浓度与断裂构造关系

以WFSD-2钻孔为研究对象,分析了随钻泥浆氢（H₂）和汞（Hg）浓度特征,在垂向上存在显著不均匀性,出现多段浓度异常高值.研究表明：（1） H₂和Hg浓度异常与次级断裂和岩石构造性质有较大关系,以断裂带或破碎带为通道运移而产生高值异常;（2）随钻泥浆H₂和Hg浓度特征暗示了汶川地震WFSD-2孔中主滑移带位置,表明随钻流体特征是识别地下裂隙带、破碎带或断裂带的途径之一;（3） H₂和Hg浓度异常还可能与构造块体边界强震活动和断裂带近场中等地震活动有关.本文研究结果为分析大震过程中深部流体活动行为提供了H₂和Hg地球化学特征依据,对地震前兆机理研究也具有重要的参考价值.     

Metamorphic,deformation, fluids and geological significance of low-temperature retrograde mylonites of Diancangshan metamorphic massif along Ailaoshan-Red River strike-slip fault zone,Yunnan, China

Diancangshan metamorphic massif is one of the four metamorphic massifs developed along the Ailaoshan-Red River strike-slip fault zone, Yunnan, China. It has experienced multi-stage metamorphism and deformation, especially since the late Oligocene it widely suffered high-temperature ductile shear deformation and exhumation of the metamorphic rocks from the deep crust to the shallow surface. Based on the previous research and geological field work, this paper presents a detailed study on deformation and metamorphism, and exhumation of deep metamorphic rocks within the Diancangshan metamorphic massif, especially focusing on the low-temperature overprinted retrogression metamorphism and deformation of mylonitic rocks. With the combinated experimental techniques of optical microscope, electron backscatter diffraction attachmented on field-emission scanning electron microscopy and cathodoluminescence, our contribution reports the microstructure, lattice preferred orientations of the deformed minerals, and the changes of mineral composition phases of the superposition low-temperature retrograde mylonites. All these results indicate that: (1) Diancangshan deep metamorphic rock has experienced early high-temperature left-lateral shear deformation and late extension with rapid exhumation, the low-temperature retrogression metamorphism and deformation overprinted the high-temperature metamorphism, and the high-temperature microstructure and texture are in part or entirely altered by subsequent low-temperature shearing; (2) the superposition of low-temperature deformation-metamorphism occurs at the ductile-brittle transition; and (3) the fluid is quite active during the syn-tectonic shearing overprinted low-temperature deformation and metamorphism. The dynamic recrystallization and/or fractures to micro-fractures result in the strongly fine-grained of the main minerals, and present strain localization in micro-domians, such as micro-shear zones in the mylonites. It is often accompanied by the decrease of rock strength and finally influences the rheology of the whole rock during further deformation and exhumation of the Diancangshan massif.     

郯庐断裂带南段韧性剪切带糜棱岩化过程中长石成分和结构状态变化特征的研究

在对郯庐断裂带南段３条韧性剪切带中糜棱岩及围岩进行矿物组合、结构构造观察研究的基础上,对长石矿物进行了多项分析测试,发现长石成分及其结构状态参数的变化与构造应力场的构造作用存在明显的对应关系：随剪切变形作用的加强,长石矿物的结构状态参数呈增大趋势,矿物单位晶胞的体积和斜长石中Ｓｉ／Ａｌ比值随之减小;长石的变形指数（Ｉｓｓ）和斜长石中的钙长石分子（Ａｎ）与岩石的变形强度呈明显的正相关关系。这些研究结果为探讨构造变形场中矿物岩石的变形 变质作用提供了一种简捷有效的手段     

基于孕震物理模式的断层气流动监测网络布设技术

为了解决我国地震地下流体流动监测网络布设中目前存在的一些问题,以“坚固体孕震模式”为理论基础,以西秦岭北缘断裂带为研究对象,通过高密度地下流体背景值探测,结合地壳垂直形变特征以及地震活动性特征,寻找区域活动断裂带流体与形变以及地震活动的耦合段及断层气响应的灵敏点,综合判断断裂带活动分段性。断层形变、地震活动与地下流体活动有着良好的对应性与耦合关系,震源区均表现为“断层闭锁区”特性,发震地点都显示出一种相对平静的状态。基于以上研究,形成从活动断裂带—“坚固体”闭锁段—近震区前兆场地的追踪思路,规划具有一定物理预报思想的标准化断层气流动观测方案,并建立研究区域观测网络的雏形。这对今后全国地震重点危险区流体流动监测台网布设提供技术思路,并为我国地震预报、震情跟踪及防震减灾工作提供重要依据。     

Fluid involvement in normal faulting

Evidence of fluid interaction with normal faults comes from their varied role as flow barriers or conduits in hydrocarbon basins and as hosting structures for hydrothermal mineralisation, and from fault-rock assemblages in exhumed footwalls of steep active normal faults and metamorphic core complexes. These last suggest involvement of predominantly aqueous fluids over a broad depth range, with implications for fault shear resistance and the mechanics of normal fault reactivation. A general downwards progression in fault rock assemblages (high-level breccia-gouge (often clay-rich) → cataclasites → phyllonites → mylonite → mylonitic gneiss with the onset of greenschist phyllonites occurring near the base of the seismogenic crust) is inferred for normal fault zones developed in quartzo-feldspathic continental crust. Fluid inclusion studies in hydrothermal veining from some footwall assemblages suggest a transition from hydrostatic to suprahydrostatic fluid pressures over the depth range 3–5 km, with some evidence for near-lithostatic to hydrostatic pressure cycling towards the base of the seismogenic zone in the phyllonitic assemblages. Development of fault-fracture meshes through mixed-mode brittle failure in rock-masses with strong competence layering is promoted by low effective stress in the absence of thoroughgoing cohesionless faults that are favourably oriented for reactivation. Meshes may develop around normal faults in the near-surface under hydrostatic fluid pressures to depths determined by rock tensile strength, and at greater depths in overpressured portions of normal fault zones and at stress heterogeneities, especially dilational jogs. Overpressures localised within developing normal fault zones also determine the extent to which they may reutilise existing discontinuities (for example, low-angle thrust faults). Brittle failure mode plots demonstrate that reactivation of existing low-angle faults under vertical σ₁ trajectories is only likely if fluid overpressures are localised within the fault zone and the surrounding rock retains significant tensile strength. Migrating pore fluids interact both statically and dynamically with normal faults. Static effects include consideration of the relative permeability of the faults with respect to the country rock, and juxtaposition effects which determine whether a fault is transmissive to flow or acts as an impermeable barrier. Strong directional permeability is expected in the subhorizontal σ₂ direction parallel to intersections between minor faults, extension fractures, and stylolites. Three dynamic mechanisms tied to the seismic stress cycle may contribute to fluid redistribution: (i) cycling of mean stress coupled to shear stress, sometimes leading to postfailure expulsion of fluid from vertical fractures; (ii) suction pump action at dilational fault jogs; and, (iii) fault-valve action when a normal fault transects a seal capping either uniformly overpressured crust or overpressures localised to the immediate vicinity of the fault zone at depth. The combination of σ₂ directional permeability with fluid redistribution from mean stress cycling may lead to hydraulic communication along strike, contributing to the protracted earthquake sequences that characterise normal fault systems.     

Structure and deformational character of strike-slip fault zones

Strike-slip fault zones observed either in the field or in model experiments generally consist of several subparallel faults which make these zones complicated in geometry and kinematics. The geometry of a strike-slip fault or shear zone is dependent on arrangement (pinnate or en echelon), on step (left step or right step), and on the rank )smaller faults within larger faults) of the subparallel fault. The relations and interactions of these three factors create a variety of dynamic circumstances and tectonic settings within the strike-slip fault zones. These include pull-aparts in the release area between subparallel faults, push-ups in the jogs where the subparallel faults overlap, and pivotal movements, or rotation, of single faults along the whole fault zone. Each kind of tectonic setting is in itself characteristic, each setting consists of many subtypes, which are controlled chiefly by the geometric parameters of the subparallel faults. One of the most important phenomena revealed in the field work is two different kinds of evolution of strike-slip fault zones: one is the evolution of a zone with a tensile component, which is related to the growth of rock bridges, and the other, of one with a compressional component, which develops by the destruction of rock bridges. In this paper we discuss, on the basis of recent research on four strike-slip fault zones in China, the essential characteristics of strike-slip faults and the possible causes of the observed structural phenomena. Attention is focussed on the deformation, development, and distribution of horizontal displacements within strike-slip fault zones.     

超低渗透率测量仪的测试标定及初步测量结果

低渗-超低渗透率测量是流体渗流力学和岩石物理学研究领域的热点问题.断层带流体输运的定量化研究对于了解断层的力学性质和预测地下流体的流动具有重要意义.文中介绍了新研制的超低渗透率测量系统和工作原理.这套设备使用稳态法和目前逐渐流行的孔隙压力振荡法进行测量,其孔隙流体为蒸馏水和氮气,最高围压可达200M Pa,孔隙压上限为...     

龙门山断裂带多参数深部结构成像与地震成因研究

通过反演大量的纵、横波地震数据,获得了沿龙门山断裂带及周边区域的深部三维精细结构,结合前人二维大地电磁探测研究成果,提出龙门山断裂带地壳形变与深部速度结构和导电率不均匀性有关,探讨了2008年汶川和2013年芦山地震的诱发和产生与流体侵入及地壳形变的密切关系.本研究发现,2008年汶川地震发生在高速度、高泊松比和低电导率的区域,2013年芦山地震则位于高速度、低泊松比和低电导率的发震层.在上地壳中,四川前陆盆地的低速、低泊松比和低阻异常与松潘一甘孜地块的高速、高泊松比和高阻异常形成了鲜明的对比.在龙门山断裂带下方的两个低速和低阻块体,将龙门山断裂带分成南、中和北三段.我们的研究认为,这两个异常体与来自松潘甘孜地块的下地壳和(或)上地幔的局部熔融或流体侵入到龙门山断裂带的脆弱区有关.基于对汶川和芦山地震的余震分布特征及震源区的地震波速度、泊松比及电阻率参数分析,揭示了龙门山断裂带深部剧烈的地壳形变与流体应力积累对2008年汶川和2013年芦山地震的触发及其地震破裂过程具有重要的控制作用.     

广西龙滩水库地壳QS二维成像

本文收集了广西龙滩水库地震监测台网2006年9月至2016年12月精定位后的3 382次M_L≥0地震的数字波形资料,采用二维衰减成像技术获得了龙滩水库库区的Q_S二维分布图像。结果显示:龙滩水库库区Q_S的横向不均匀变化明显,Q_S低值区围绕着库区近似呈环形分布;在Q_S低值分布区附近,大多为河流与断裂带的交汇处;Q_S低值分布主要对应于透水性较强的岩性地区。以上现象表明Q_S低值分布受水、断裂、岩性等3种因素的影响,由此初步推断库水可能沿着断裂上的岩石破碎带及节理、裂隙发育地区和具有较强透水性岩层区域向下渗透,使得岩石孔隙中充满流体,内摩擦增大,地震波剧烈衰减,从而使Q_S值大幅下降。结果还表明:大多数地震发生在Q_S高、低值过渡区域,这种“软”、“硬”介质的交界处,容易积累应变能,孕育地震。这是由于当Q_S高、低值过渡区域受到水的加载作用及其对裂隙边界的润滑作用,发震断层的抗剪强度降低,使滑动容易产生,从而诱发地震。      

THE GEOLOGICAL AND ROCK MECHANICAL DISTINCTION EVIDENCE BETWEEN STICK-SLIP AND CREEP IN HOST ROCK SEGMENTS OF FAULT

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.     

The use of local seismic networks for identifying the seismogenic structure of faults

We consider a method for identifying the segments of localization of deformation processes within fault zones. The method is based on the results of seismic monitoring at a dense seismic network in California. For the first time, by analyzing the seismogenic structure of several fault zones, we highly accurately located the domains involved in active deformation processes. Three-dimensional reconstructions show that these domains are a set of local segments each having a characteristic size of about 100 m, which is commensurable with the scale of the probable anthropogenic impacts on the geological medium.     

基于中速-高速摩擦实验研究含碳断层带的电导率特征

野外地质调查结果显示,断层带常富集碳质.断层带中碳的分布结构是影响断层带电导率特征的一种重要参数.本文在室温、室内湿度和2MPa正应力条件下,对不同石墨含量(3,5,6和7wt%)的石英-石墨混合断层泥模拟样品开展了滑动速率介于500μm·s-1～1m·s-1的摩擦实验及相应的电导率测量,以期研究断层运动对碳分布结构的影响以及断层带电性特征对碳含量及分布的响应情况.结果显示,摩擦滑动能够显著地改变样品的电性特征(电导率大小及其各向异性).在平行滑动面方向(径向),样品电导率随着滑动位移的增加快速增加,在滑动约数十厘米之后,其电导率基本达到稳定状态;在垂直滑动面方向(轴向),样品电导率基本不随摩擦滑动速率和滑动距离而变化.SEM显微结构观测显示,摩擦滑动所引起的电导率各向异性直接反映了石墨分布结构的变化.该研究结果深化了对地震断裂带浅部电性特征的认识,为野外断层带大地电磁测深资料的解释提供了约束,同时对于了解含碳断层的力学性质和弱矿物相在剪切变形中的分布特征及其演化过程等方面也具有重要意义.     

Distribution of fault rocks in the fracture zone of the Nojima Fault at a depth of 1140 m: Observations from the Hirabayashi NIED drill core

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.     

北京地区的水平形变及其构造含义

本文重新处理了1976—1980年用激光测距对北京地区的一等三角网进行复测所得到的资料。在此基础上分析研究了北京地区水平形变场的特征,结合地震地质资料讨论了它在构造上的含义。文章主要用伸展构造的观点解释了北京地区几个压应变带形成的原因和可能的活动机制