对一个地震突变模型的讨论   总被引：4，自引：0，他引：4  

殷有泉  杜静 《中国地震》1994,10(4):363-370

本文用非线性力学方法讨论了地震过程的非稳定现象并建立了相应的突变理论模型。文章详细讨论了断层带的本构性质和突变模型中状态变量的选取对地震非稳性的影响，揭示了用突变模型研究地震现象的可行性。  相似文献   

Jadeitites, albitites and related rocks from the Motagua Fault Zone, Guatemala   总被引：12，自引：0，他引：12  

G. E. HARLOW 《Journal of Metamorphic Geology》1994,12(1):49-68

Jadeitites from Guatemala are found as weathered blocks in tectonized serpentinite in a 15-km zone north of the Motagua Fault Zone. Rock types found with jadeitite include albitites, albite-mica rocks, omphacite/taramitic amphibole-bearing metabasites, chlorite-actinolite schists, talc-carbonate rocks and antigorite schists. In addition to the predominant jadeitic (Jd₉₃_₁₀₀) pyroxene, common phases in jadeitite include micas (paragonite and/or phengite ± rarer phlogopite), omphacite, albite, titanite /Pm zircon, apatite and graphite. Conditions of jadeitite formation are 100-400d? C, 5-11 kbar with 0.0 > log₁₀a_sio2≥= 0.7. Fluid inclusions, coarse textures, vein structures, and rhythmic zoning of pyroxene indicate an aqueuos fluid was involved. Jadeitites are either (1) metasomatic modifications of former felsic-to-pelitic inclusions that have undergone silica depletion plus efficient soda exchange and enrichment, or (2) solution precipitations derived from such a source. The close spatial relationship of faults and shear zones, serpentinites, and jadeitites suggests jadeitites form in a relatively high-P/T setting with substantial flow of sodic fluid in a tectonized zone. Most Guatemalan jadeitites are extensively altered to analcime, albite, taramitic amphibole, (clino)zoisite ± nepheline and preiswerkite. This alteration reflects depressurization /Pm heating to below the jadeite + fluid = analcime reaction at high a_Na. With progressive alteration, analcime and nepheline are replaced by albite; the increase in silica content may result from fluid flowing up a tectonized zone reaching saturation with an albite assemblage. Albitite phases, albite, actinolite, zoisite, /Pm chlorite, phengite, K-feldspar and quartz, record conditions of c. 3-8 kbar at T < 400d? C, indicating a clockwise P-T trajectory of the blocks. Barium aluminosilicates—banalsite, celsian, cymrite and hyalophane—are common minor late-stage phases in jadeitites and albite-rich rocks. Barian phengite is common in albite-mica rocks.  相似文献   

随县-马鞍山地带地壳与上地幔结构及郯庐构造带南段的某些特征   总被引：8，自引：0，他引：8       下载免费PDF全文

郑晔  腾吉文 《地球物理学报》1989,32(6):648-659

本义利用1979-1981年中国科学院地球物理研究所在随县-马鞍山所做的人工源地震探测的资料,采用二维射线追踪来拟合地震波的走时和振幅,取得了该地带的地壳与上地慢速度结构.结果表明,该地带地壳厚度为32-37km,莫霍面起伏变化显著.地壳速度的横向变化甚为强烈,地壳中部存在低速层.在巢湖以西宽数10km的范围内,地壳结构与其它地方明显不同,上地壳速度明显偏高,莫霍面上隆并有间断;在其两侧,明显可见有两条深断裂.结合其它地球物理场特征及大地构造概况,对结果进行分析,认为郯庐构造带南段被两条深断裂所夹,构造带宽度可达数10km,并在地质历史时期曾有过地幔物质上涌.  相似文献   

Can injection tests reveal the potential for fault movements?     

J. Noorishad  P. A. Witherspoon 《Pure and Applied Geophysics》1984,122(2-4):608-618

The role of fluids in faulting mechanism and triggering earthquakes is widely accepted. The effective-stress law is the basis for the postulated theories. Using a generalized version of this law, applicable to both continuum and discontinuities, hydromechanical behaviour of a horizontal fracture in a hypothetical fluid-injection problem is investigated. In this problem the increasing intake flow rates, unpredictable by the traditional fluid-flow solutions, brings out another significant aspect of the role of the fluid pressure in rocks. By reducing the magnitude of the compressive effective stresses the fluid pressure causes elastic recovery in fractures. Simple rheologic models are used to demonstrate this fact. Such effects may lead to permeability increases in the rock mass, depending on the magnitude of the fluid pressure. Such variations in permeability, however, are governed by the path dependency of the fracture-deformation response. Therefore, a significant increase in permeability is an indication of comparability of the state of stress and the applied fluid pressure.This index may reveal the potential of hydroactivation of faults, as may arise in the regions of dam reservoirs, underground waste injections, and known faults, for certain ranges of working pressures relevant to each of the above-cited situations. Fluid-injection tests under constant working pressures are suggested as a means revealing the likelihood of movement on the faults.  相似文献   

Fault interaction and seismicity: Laboratory investigation and its seismotectonic interpretation   总被引：2，自引：0，他引：2  

A. piák  T. Lokajíek 《Pure and Applied Geophysics》1986,124(4-5):857-874

Systems of two parallel linear faults of the same length with the angle of inclination =45° were investigated under uniaxial linearly increasing load. Perspex plates were used as models. For each treated fault configuration the morphology of tensile cracks and the sequence of seismoacoustic events of shear and tensile origin were studied.It is shown that the seismic regime of a fault system is strongly influenced by the contact conditions on a fault plane; it is different in the faults with the aseismic contact, represented by open slits, and in the faults with the seismoactive contact, represented by filled slits, respectively.The experiments proved the dominating role of a fast shear displacement of the stick-slip type in the regime of seismic energy release of a fault system. The tensile crack generation seems to be only of little—if not negligible—importance. On the other hand, the existence of tensile cracks in a fault system can play an important role in the course of subsequent loading cycles because the stick-slip displacements can take place not only along the primary faults but also along the planes of tensile cracks.A comparison of some results of model experiments and the already published results of geological and seismological investigations indicated that the way of seismic energy relase on faults in nature and in the laboratory could be of the same character. Several analogies between the seismic regime of a fault model and of real seismic regions were found concerning the morphology of faults, off-fault fore- and aftershocks, and earthquake doublets, respectively.  相似文献   

Fault dimensions,displacements and growth   总被引：15，自引：0，他引：15  

Juan Watterson 《Pure and Applied Geophysics》1986,124(1-2):365-373

Maximum total displacement (D) is plotted against fault or thrust width(W) for 65 faults, thrusts, and groups of faults from a variety of geological environments. Displacements range from 0.4 m to 40 km and widths from 150 m to 630 km, and there is a near linear relationship betweenD andW ². The required compatibility strains (e _s) in rocks adjacent to these faults increases linearly withW and with and ranges frome _s=2×10^–4 toe _s=3×10^–1. These are permanent ductile strains, which compare with values ofe _s=2×10^–5 for the elastic strains imposed during single slip earthquake events, which are characterised by a linear relationship between slip (u) andW.The data are consisten with a simple growth model for faults and thrusts, in which the slip in successive events increases by increments of constant size, and which predicts a relationship between displacement and width of the formD=cW ². Incorporation of constant ductile strain rate into the model shows that the repreat time for slip events remains constant throughout the life of a fault, while the displacement rate increases with time. An internally consistent model withe _s=2×10^–5, giving repeat times of 160 years and instantaneous displacement rates of 0.02 cm/yr, 0.2 cm/yr, and 2.0 cm/yr when total displacement is 1 m, 100 m, and 10 km, and slip increasing by 0.5 mm with each event, gives a good approximation of the data. The model is also applicable to stable sliding, the slip rate varying with ductile strain rate and withW ².  相似文献   

甘肃古浪、景泰活断层上的树木地震学研究   总被引：2，自引：0，他引：2       下载免费PDF全文

杨斌  刘百篪 《地震地质》1995,17(2):139-147

在树木地震学测年技术研究的基础上，沿古浪活断层西段鉴定和评价了数百棵树。对树木生长速率及年轮比率低值偏离的３种类型进行了有效的识别。结果表明：断崖上被破坏的青海云杉中，记录的结构和生长速率异常，可以归因于１９２７年５月２３日古浪８级大地震的影响。从而为古浪地震断层的判定提供了准确的年代证据。并将前人认为的古浪地震断层位置向冷龙岭北麓南移了３０余公里。用该方法在老虎山活断层上对１８８８年１１月２日景秦６１／４级地震破裂带定年，再次获得成效  相似文献   

郯庐断裂带平移时代的同位素年龄证据   总被引：82，自引：6，他引：82       下载免费PDF全文

朱光  徐嘉炜  孙世群 《地质论评》1995,41(5):452-456

对郯庐断裂带南段左旋走滑韧性剪切带中糜棱岩的K-Ar全岩分析结果研究表明,该剪切带形成后,在99±2Ma前(早白垩世末期)冷却至封闭温度。结合其它地质现象,笔者认为郯庐断裂带大规模左行平移发生在早白垩世末期,推测为110—130Ma前。这一平移时代与太平洋的伊泽奈崎(Izanagi)板块向欧亚大陆斜向俯冲的时间基本一致。  相似文献   

构造活动地区工程构造稳定性研究     

刘行松  钟嘉猷 《工程地质学报》1995,3(1):1-9

拟建的新疆喀拉喀什河乌鲁瓦提水电站位于现代地壳运动十分活跃的区域。野外证据显示出，坝区的Ｆ＿（１２）断层新活动延续到晚更新世，电站附近的石门北断层在第四纪有活动。对采自坝区及附近几条断层的断层物质样品进行了变形显微构造、石英颗粒表面形貌和微结构类型、ＴＬ年龄的分析测定，结果表明，Ｆ＿（１２）最新活动的上限时间不晚于３万年，Ｆ＿（３０）和石门断层的活动持续到晚更新世，石门北断层最新的活动的上限时间约２万年。根据区域断裂的分布和应力场的情况，进行了构造模拟实验，预测出工程区在区域应力场的继续作用下，应力集中在远离坝址的部位，坝址附近不会出现新的应力集中点。总体看，所选坝址是地壳活动区中相对较稳定的地段。  相似文献   

郯庐断裂系研究的新进展─—兼论东亚北东向走滑断裂系统     

刘先文  单巨仁 《地球科学进展》1995,(2)

对郯庐断裂系研究的最新进展作了介绍。郯庐断裂是多期活动、性质多次转换的巨型断裂。最初的启动时间在晚三叠世末，与南北大陆的碰撞有着直接的关系。早期以走滑（左行）运动为主，伴随挤压和拉伸，范围限于华北地块内部。断裂纵向伸展的高峰期为白垩纪到早始新世，这一时期也是裂陷作用最强的时期。始新世以来以挤压作用为主。东亚走滑断裂系各组成断裂性质复杂，不能以中生代左行平移运动简单概括。走滑断裂系的发展和演化与同时期大陆边缘所处的地球动力学环境，也就是与南北大陆的碰撞和古大洋板块的持续俯冲关系密切。新生代以来的构造事件使中生代的构造发生强烈变形变位改造。  相似文献