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1.
本文通过地壳应力测量结果和地震资料的综合分析,对深部应力状态与断层运动的关系作了讨论:进而应用库仑准则,推导了三维应力作用下完整岩体和已有的任意空间方向断层面的失稳条件及其滑动方式的解析表达式.通过建立描述岩体和已有断层稳定性的两个函数————破裂函数 Fm 和摩擦函数 Ff,给出了应用破裂机制和摩擦滑动机制综合分析地壳稳定性和失稳性态的方法:根据这种分析方法并结合华北平原区的水压致裂应力测量资料,以及孔隙压力、大地热流等观测结果,定量研究了本区地壳的稳定问题,计算并图示了地壳内破裂函数沿深度的分布,以及各种走向和倾向断层面上的摩擦函数和剪应力分布;计算中以 Byerlee 定律作为断层运动的约束条件,并考虑了地壳密度纵向非均匀性导致的垂直应力沿深度的非线性增长以及深部超静水压力的异常孔隙压力作用.结果表明,华北平原区地壳失稳性态主要表现为已有断层的滑动;伴有高剪应力降的断层运动的深度范围在8至2.0多公里之间:陡断层稳定性低于缓断层,其运动方式以走滑为主;本区 NNE-NE 走向的陡断层是一组易震断层,其震时错动为右旋走滑;孔隙压力的增长对地壳稳定性有显著的影响;华北平原区深部高异常孔隙压力是地震活动的一种重要背景. 相似文献
2.
Summary The distance of stable sliding before sudden slip on fault surfaces in granite decreases rapidly as the confining pressure is increased. At a pressure of 6 kb the amount of stable creep is very small or absent. Two orders of magnitude change in strain rate has no effect on the distance of stable sliding. Our results suggest that in the earth, fault creep should predominate in the shallow crust but in the deep crustal layer most of the stresses are probably relieved by sudden earthquake type of motion. Below the crust high temperature would promote stable-slip so in this region creep would once more predominate. 相似文献
3.
We present the geophysical evidences on the role of fluids for generation of the lower crustal Jabalpur earthquake (21 May 1997, mb 6.0, Mw 5.8), in the mid-continental fracture zone of the Indian Peninsular Shield. With a focal depth of 35 km, it indicates a high angled (< 62∘ enclosed with maximum principal stress direction) reverse fault with small component of left-lateral strike slip in the lower crust. The Son-Narmada-Tapti (SONATA) magalineament, during the past two centuries, has experienced about 25 moderate to strong earthquakes; two of which namely the Son Valley (1927, M 6.5) and Jabalpur (21 May 1997) were disastrous. Historical earthquakes and recent earthquake swarms indicate a moderate to high seismicity in SONATA belt that is due to high strain accumulation, flexuring of the crust and neotectonic movements of the faults in the rift zones. By analyzing geophysical parameters such as Zero-Free air-based (ZFb) gravity anomalies (∼ −10 to –30 mGals), heat flow values (45–47 mWm−2), magneto-telluric values (1- Ohm m), strain rate (1.5 × 10−8) and failure stress conditions, we identify plausible causative factors for the occurrence of lower crustal earthquake in this region Fluids, due to dehydration of serpentinite in the lower crust, are suggested to be present in the earthquake source zone. The estimated pore-fluid factor for the Jabalpur earthquake (λ
v
) is 0.95. The diffusion of pore-pressure relaxation, represented as pressure perturbation generated by coseismic stress change was seen in the form of swarm activity two years prior to the Jabalpur earthquake. We suggest the existence of a deep pre-fractured zone with low shear stress (τ = 15–18 MPa) that indicates the presence of fluid filled fractured mafic material in the felsic crust, in critical state of unstable failure condition, and also fluid driven migration of swarm activity before the Jabalpur earthquake. 相似文献
4.
Crust and uppermost mantle structure of the Ailaoshan-Red River fault from receiver function analysis 总被引：5，自引：1，他引：5
XU Mingjie WANG Liangshu LIU Jianhua ZHONG Kai LI Hua HU Dezhao XU Zhen 《中国科学D辑(英文版)》2006,49(10):1043-1052
S-wave velocity structure beneath the Ailaoshan-Red River fault was obtained from receiver functions by using teleseismic body wave records of broadband digital seismic stations. The average crustal thickness, Vp/Vs ratio and Poisson’s ratio were also estimated. The results indicate that the interface of crust and mantle beneath the Ailaoshan-Red River fault is not a sharp velocity discontinuity but a characteristic transition zone. The velocity increases relatively fast at the depth of Moho and then increases slowly in the uppermost mantle. The average crustal thickness across the fault is 36―37 km on the southwest side and 40―42 km on the northeast side, indicating that the fault cuts the crust. The relatively high Poisson’s ratio (0.26―0.28) of the crust implies a high content of mafic materials in the lower crust. Moreover, the lower crust with low velocity could be an ideal position for decoupling between the crust and upper mantle. 相似文献
5.
2008年汶川地震后,为查明北京地区现今地应力状态、评价断裂稳定性,相继在北京地区开展了5个深孔（600~1000 m）的水压致裂法地应力测量,并在适宜深度安装了地应力相对变化监测探头,建立了地应力变化监测台站.本文首先利用实测地应力数据分析了北京地区地壳浅表层应力状态,结果表明：（1）北京地区千米深度内,最大、最小水平主应力随深度增加梯度系数分别为0.0328和0.0221,侧压系数Kav和KHv值,最大、最小水平主应力之比KHh值与国内外已有认识基本一致,而水平向剪应力相对强度参数μm值较低;（2）北京地区最大水平主应力优势方向为近EW向,与华北地区构造应力场方向基本一致,同时受区内断裂活动等影响,存在与区域主应力方向偏差的局部应力场;（3）实测数据揭示的应力结构显示,北京地区地壳浅表层最大主应力（σ1）总体为最大水平主应力（σH）,受区域构造演化以及测点附近断裂的影响,中间主应力（σ2）与最小主应力（σ3）所对应的实测地应力存在变化,但总体来讲,实测地应力数据揭示的应力结构与北京地区主要断裂性质基本相吻合.其次,基于实测应力数据,采用库仑摩擦滑动准则,结合拜尔定律,并取摩擦系数为0.2~1.0,初步评价了北京地区主要断裂稳定性,结果显示：（1）在摩擦系数取0.6~1.0条件下,北京地区现今应力状态尚未达到导致断裂失稳滑动水平,断裂不会出现失稳滑动现象;（2）摩擦系数弱化到0.4时,西峰寺钻孔应力状态满足断裂失稳滑动条件,揭示出八宝山断裂存在失稳滑动可能性,而夏垫-马坊断裂和黄庄-高丽营断裂附近测点应力状态将趋近满足断裂失稳滑动条件,表明这两条断裂有趋向失稳滑动可能性;（3）只有当摩擦系数弱化到0.2时,北京地区主要断裂才可能在现今应力状态出现断裂失稳滑动.本文的认识对北京地区乃至华北地区构造应力场、地震地质研究有重要参考意义. 相似文献
6.
Receiver function structures beneath the Haiyuan fault on the northeastern margin of the Tibetan plateau 
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下载免费PDF全文 We performed a receiver function analysis on teleseismic data recorded along two dense seismic profiles and from 4 broadband regional seismic stations across the northeastern Tibetan plateau. The crustal thickness and vP/vS ratio were measured by the H-κ domain search algorithm. The Moho discontinuity across the Haiyuan arc fault zone was also revealed by common conversion point (CCP) imaging. Our study results show that the crustal thickness and the vP/vS ratio were 42–56 km and 1.60–1.88, respectively. The crustal thickening on the northeastern margin indicates that the crust is shortening or that there was a superimposition of crusts during the collision of the Tibetan plateau with Eurasian block. Our results suggest that Haiyuan fault likely resulted from the interactions of high temperature and pressure conditions during the collision of the Indian and Asian continents. The Moho beneath the Haiyuan tectonic region exhibits an obvious offset and a vague discontinuity according to CCP imaging. This study suggests that the Haiyuan arc fault zone is a trans-crustal fault that cuts through the Moho in the northeastern Tibetan Plateau. Moreover, there are indications of strong deformation in the intensive crustal extrusion from the interior of the Tibetan Plateau to its northeastern margin. 相似文献
7.
A model, in which various seismic environmental factors are involved, has been developed in the paper on the bases of relevant
data. The environmental factors include the crust structure, lithological conditions, fault plan attitude, the crust stress
state, pore-fluid pressure and geothermal conditions, etc. The effect of each of the factors on the tectonic movement energy index has been analyzed. The model calculation results
indicate that shear fracture energy of a fault generally increases with depth; it reached a peak value at a certain depth,
then turns gradually attenuated. Of all the factors, the effects of pore-fluid pressure and geothermal conditions on the energy
index are of prominence. High pore-fluid pressure and high temperature circumstance may result in decline of the peak value
of the shear fracture energy curve, making the depths of the peak value and of the bell-waist value deepened. Such effects
restrict strong seismic events, but suitable for micro-seismic activity and/or fault creep. The lower limit of focal depth
under such an environment is relatively deep. Contrarily, low pore-fluid pressure and low geothermal temperature circumstance
result in increase of the peak value of the shear fracture energy curve, and the curve becoming steep. The later circumstance
is favorable to the formation of locked segment where possesses high strength and high-energy accumulation. If these two kind
of segments are arranged interactively along a fault zone, such arrangement would boost the energy transition among the segments,
forming mechanical circumstance of energy highly accumulated in one segment with adjacent segment(s) less-locked. Such contrast
of the strength and energy would provide conditions for strong earthquakes with high stress drop. An analysis of the northwest
segment of the Honghe fault has provided some evidence for the modeling results.
Foundation item: Chinese Joint Seismological Science Foundation (No. 9507424). 相似文献
8.
利用云南和中国地震台网30个台站记录的远震资料,采用接收函数扫描法和线性反演方法对云南及其邻区的壳幔速度结构进行了研究,获得了研究区内地壳厚度、Vp/Vs以及壳幔速度的分布特征.利用接收函数扫描（H-k）法和线性反演方法获取的台站下方地壳厚度结果表明,研究区地壳厚度变化剧烈.速度结构研究结果表明,红河断裂以西的腾冲-保山地块和思茅地块,以及南华板块北部地区的台站（如攀枝花、丽江、东川、永胜等）下方地壳均存在下地壳低速层,且具有高的地壳平均Vp/Vs值.这些不仅暗示研究区的下地壳低速异常可能为高温甚至高温导致的部分熔融所致,同时,也意味着该区下地壳的物质易于发生塑性流动,为地壳的变形和增厚创造了条件.红河断裂带作为云南地区的一个主要边界断裂,其西侧地区地壳厚度变化较东侧剧烈,另一方面,红河断裂西侧的平均地壳Vp/Vs值较其东侧要高.综合前人关于研究区岩石圈速度结构、地热流值、重力场和上地幔各向异性等地球物理场的研究结果.我们推断,现今的思茅块体和保山-腾冲块体在大地构造上应归属于冈瓦纳板块. 相似文献
9.
By means of the hypocenter distribution and focal mechanism of Wuding MS=6.5 earthquake sequence occurred in 1995, the space orientation and activity characteristics of focal fault of Wuding earthquake have been studied from the three-dimensional space-time process. The results indicate that the focal fault of Wuding earthquake is a subsurface, NWW-trending, upright and right-lateral strike slip fault which is consistent with the intensity distribution in the meizoseismal region. Although the large-scale NS-trending Tanglang-Yimen active fault passes through the earthquake region, it is irrelevant to the MS=6.5 Wuding main earthquake. Since the relationship between the strong earthquake and the shallow geological active fault can not be determined, the crustal deep structure should be studied. The method proposed in the paper can be used to distinguish the focal fault in the deep crust. 相似文献
10.
The Baikal is a deep long and narrow basin in East Siberia which follows a huge fault zone adjoining the Siberian Platform. The basin was formed by rapid subsidence of continental crust during the pas 3–4 Ma. It is bounded by normal faults which indicate extension of the crust during the subsidence. According to seismic reflection profiling data, the intensity of extension is not large (3–7%). It is much smaller than the thinning of the crystalline crust under the basin (up to 38%). The thinning and crustal subsidence can be explained by the transformation of gabbro in the lower crust into dense garnet granulites. The latter rocks (with Vp 7.7−7.8 km/sec) are still located under the remnant part of the crust. Rapid transformation took place due to an inflow of catalyzing fluid along the fault zone from the asthenospheric upwelling. This upwelling, which is at a depth of 80–90 km, caused a general uplift of a broad area in the south of East Siberia. 相似文献
11.
THE GEOLOGICAL AND ROCK MECHANICAL DISTINCTION EVIDENCE BETWEEN STICK-SLIP AND CREEP IN HOST ROCK SEGMENTS OF FAULT 下载免费PDF全文
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
12.
The Bob-Tangol earthquake of magnitude 5.8 (MS), occurred in southeastern Iran on 19 December 1977, not far from the region where the 1896 and 1933 earthquakes caused considerable damage and destruction. The shock was associated with a 19.5-km fault break at the surface with a maximum 20 cm right-lateral strike-slip movement along an Early Quaternary geological fault. Results of the field investigation together with the fault plane solution and epicentre location of the main shock are presented here in order to give a seismotectonic view of the event.Surface rupture and fault plane solution of this medium-magnitude earthquake demonstrate a considerable amount of right-lateral movement along a major Early Quaternary high-angle reverse fault. This change in fault behaviour and slip vector may indicate that evidence of Early Quaternary movement cannot always provide a good clue to present-day crustal deformation. 相似文献
13.
14.
地下水诱发的浅层前兆异常及其机理与有关的地震预报问题(1) 总被引：17，自引：1，他引：16
依照“源、场、外”相结合的地震科学研究思路,提出地下水诱发浅层前兆异常机理。认为降水等因素造成的地下水动态变化,可产生一种作用于地壳岩石的附加流体力;地震前,通过多种流体力作用,引起已经积累较高应力的地壳应力－－应变场调整变化,并使岩石强度改变,从而促进与诱发浅层地壳的构造变动;其结果是派生或伴生出地形变、地应力、水化学及地电阻率等多种浅层前兆异常。在降水、地下水的多种周期变化成分中,只有那些能与地壳应力－应变过程产生力学耦合的周期变化,才能调制与诱发出异常,这一部分变化可做为广义的地震前兆。孔隙压力、动水压力以及化学腐蚀等原理,是该异常机理的理论基础。列举出六方面的事实做为该机理直接的或间接的证据。 相似文献
15.
Constraining the crustal structure under the central and western Tian Shan based on teleseismic receiver functions and gravity anomalies 下载免费PDF全文
下载免费PDF全文 The Tian Shan is a vast range that spans several countries in Asia. Understanding its evolutionary history may provide valuable insights into intracontinental orogenic dynamics. In this study, we explored the crustal characteristics of the Tian Shan and their relationships to the tectonic evolution of the region. A new H-stacking method that combines the P receiver function and gravity anomalies was used to estimate the thickness and ratio of P- to S-wave velocities (vP/vS) for 91 broadband seismic stations in the central and western Tian Shan. Our results revealed significant lateral variations in crustal thickness and vP/vS. A ~45-km-thick crust and an intermediate-high vP/vS (~1.74–1.84) were found in the Kazakh Shield and Tarim Basin, which we interpreted to indicate a mafic crystalline basement and lower crust. The central Tian Shan varied greatly in crustal thickness (40–64 km) and vP/vS ratio (1.65–2.00), which may be due to crustal shortening, mafic underplating, and crustal melting. In contrast, we observed a relatively thin crust (42–50 km) with an intermediate vP/vS ratio (~1.78) in the western Tian Shan. The differences in the crustal structures between the western and central Tian Shan imply that the Talas-Fergana Fault may be trans-lithospheric. 相似文献
16.
为了建立断层蠕动与其周围地壳形变的关系, 本文给出了线性粘弹性半空间中任意倾角的断层滑动引起的准静态位移场的完整的解析表达式.其中, 滑动时间函数的形式是根据经验拟定的, 而介质被视为广义开尔文体或麦克思韦体.通过数值计算讨论了介质的流变性对位移场的影响.根据1976年唐山地震前后在地震区取得的短期观测资料的分析, 论证了唐山主震前夕在极震区地壳上部曾发生过前兆蠕动, 而且主震后断层仍继续滑动, 但其速率呈指数型衰减.估算了符合观测数据的断层滑动参数, 并对这些结果的意义作了简要的讨论. 相似文献
17.
为深入研究1997年新疆伽师地区连续发生的强震群的震源破裂特征,利用全球数字地震台网(GDSN)宽频带数字资料及区域台网资料,较详细地研究了伽师强震群的震源机制及震源破裂特征.结果表明:伽师强震群的震源机制解主要有走滑和正倾两种破裂类型,其共同特点是主压应力轴方向沿北北东向,主张应力轴沿北西向,与区域构造应力场方向存在差异,具有明显局部特征;从震源破裂特征来看,伽师强震的滑动尺度、上升时间和持续时间均较小,震源破裂面积不大,是由一点向四周快速扩散的脆性破裂,无明显伸展方向;伽师强震群的破裂断层面为北东向,与震源深度梯度变化带、地壳接触变形梯度变化带、等烈度线以及地震扩展方向吻合;伽师强震群是在近南北向挤压环境下,在震源区附近剪切和张扭应力作用下发生的多次沿北东向的脆性快速破裂,从而造成了伽师强震群以张性破裂和左旋走滑为主的震源特征. 相似文献
18.
V. V. Adushkin G. G. Kocharyan V. A. Novikov 《Izvestiya Physics of the Solid Earth》2016,52(5):637-647
We present the data of the laboratory experiments on studying the regularities of gradual transition from the stick-slip behavior to aseismic creeping on the interblock boundary. The experiments show that small variations in the material composition in the principal slip zones of the faults may cause a significant change in the fraction of seismic energy radiated during the dynamic unloading of the adjacent segment of the rock mass. The experiments simulate interblock sliding regimes with the values of the scaled kinetic energy differing by a few orders of magnitude and relatively small distinctions in the strength of the contacts and in the amplitude of the released shear stresses. The results of the experiments show that the slip mode and the fraction of the deformation energy that goes into the seismic radiation are determined by the ratio of two parameters—the stiffness of the fault and the stiffness of the enclosing rock mass. An important implication of the study for solving the engineering tasks is that for bringing a stressed segment of a fault or a crack into a slip mode with low-intensity radiation of seismic energy, the anthropogenic impact should be aimed at diminishing the stiffness of the fault zone rather than at releasing the excessive stresses. 相似文献
19.
以龙门山附近区域水平运动特性以及深部岩体力学特性为基本条件,采用FLAC模拟软件计算分析了龙门山断裂带及附近区域的地貌形成过程和地应力演化机制。研究结果认为:区域板块运动是龙门山地貌形成的重要原因,龙门山3条断层在62万年内的相对滑移速率分别为1.53,0.245和0.458 mm/a,与实际监测结果基本吻合;龙门山断裂带左侧呈抬升趋势,右侧四川盆地的垂向运动保持稳定;随着区域板块的运动,3条断裂带附近主应力的变化均经历了3个阶段,即应力低态稳定阶段,应力增高阶段和应力高态稳定阶段,最终形成应力积聚—应力释放的平衡局面;断裂带附近的最大、最小主应力比值介于2.94—3.71之间,平均为3.3,与实际监测结果基本吻合。由此可以推断,龙门山及附近区域将长期处于高偏应力环境,即长期处于“应力累积—进入临界状态—发震—新的应力累积”的地震周期。 相似文献
20.
Zhengxiang Fu 《地震学报(英文版)》1992,5(2):225-235
The Kaoiki, Hawaii, earthquake with magnitude 6. 6 of November 16, 1983 was a strike-slip faulting event on a fault with large
dip angle. The results for mechanisms of smaller events before and after the Kaoiki mainshock show that there were two kinds
of mechanisms: (1) strike-slip on the fault with large dip angle; (2) slip on the crustal discontinuity plane with smaller
dip angle, and systematic and alternative changes in the mechanisms were observed.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 139–149, 1991. 相似文献