长江口海域新生代地层与断裂活动性初探   总被引：7，自引：1，他引：7  

火恩杰  章振铨  刘昌森  王锋 《中国地震》2003,19(3):206-216

长江口海域通过浅层人工地震勘察查明，新生代地层可分为5个地震层。分别为第四系、上新统、中新统上段、中新统下段及始新统。第三纪地层自东北向西南依次超覆、减薄尖灭，上部被第四纪地层不整合覆盖。沉积基底主要由晚侏罗世火山岩系及燕山晚期酸性小岩体构成，未发现早第三纪及晚白垩世断陷盆地。断裂构造很发育，按展布方向大体可归为北东、北西及近东西向3组，皆为正断层。前两者数量多、延伸长、断距大，与同区的航磁异常构架吻合。北东向断裂分段明显，西南段为第四纪断裂，中段为晚第三纪断裂，东北段为早第三纪断裂；而北西向断裂分段不很清晰。两者的垂直位移速率平均在0．015mm/a。本文对该海域有关的几个地质问题进行了讨论。  相似文献   

乌鲁木齐市华凌拟建地下停车场活断层探测与城市活断层探测手段适用性初步分析   总被引：1，自引：1，他引：1  

沈军  李军  赵纯青  葛敏 《内陆地震》2003,17(1):66-73

根据在乌鲁木齐市拟建华凌地下停车场活断层探测与地震危险性评价工作，对通过乌鲁木齐闹市区的雅玛里克断裂进行了实验性探测。采用了浅层地震探测、地质雷达探测、地形测量和坑探剖面方法，对这些手段的适用性进行了初步分析和讨论。  相似文献   

生物标志化合物与相关的全球变化   总被引：20，自引：9，他引：20  

谢树成  梁斌  郭建秋  易轶  R.P.Evershed  D.Maddy  F.M.Chambers 《第四纪研究》2003,23(5):521-528

在各种地质体中广泛分布的生物标志化合物在全球变化研究中有着广泛应用,特别是在海洋和湖泊沉积物中,研究工作已涉及到古植被、古温度、古降水量、古大气CO₂浓度和古季风等的恢复.文章介绍利用气相色谱仪、气相色谱-质谱联用仪、气相色谱-热转换-同位素比质谱仪分析了一个长40cm泥炭岩芯(约222年)的生物标志化合物的分布及其单体氢同位素.结果显示,不管是生物标志化合物的分布,还是其单体稳定同位素特征都记载了气候(温度)的变化.正构脂肪酸的碳优势指数(CPI值)、正构烷烃C23/C31比值、正构烷烃C23的δD值与温度有很好的对应关系.  相似文献   

燕山地区中元古代常州沟组潜穴化石   总被引：2，自引：4，他引：2  

刘鹏举 《地质论评》2003,49(5):522-524

在燕山地区中元古代常州沟组中发育有大量的潜穴化石，潜穴产于常州沟组中部的泥质粉砂岩中。潜穴呈个体较大的直管状，垂直层面保存。这是我国迄今为止发现的最古老的遗迹化石，表明在距今近1800Ma前就已出现古老的后生动物，这对于研究后生动物的起源及演化具有重要意义。  相似文献   

岩石断裂作用的复杂性和混沌动力学   总被引：1，自引：0，他引：1  

谭凯旋  谢焱石  陈广浩  黄晓乃 《大地构造与成矿学》2003,27(4):372-377

断裂是一个复杂的动力学体系,受到岩石结构、反应、流体迁移、应力、岩石变形和力学等多种地质因素和过程的耦合控制。本文建立了断裂体系的反应-输运-力学耦合动力学模型并编制了模拟程序。以湖南水口山矿区为例,通过动力学模拟表明不同地层岩性的断裂渗透率大小和演化特征存在显著差异,断裂作用促使岩石渗透率的空间非均匀性增强,从而有利于流体的局部汇聚和矿体的形成。断裂中压力随时间呈现出非周期振荡变化,反映了断裂演化的混沌特征。  相似文献   

Architecture of fault zones determined from outcrop, cores, 3-D seismic tomography and geostatistical modeling: example from the Albalá Granitic Pluton, SW Iberian Variscan Massif     

J. Escuder Viruete  R. Carbonell  D. Martí  M. J. Jurado  A. Prez-Estaún 《Tectonophysics》2003,361(1-2):97-120

The 3-D seismic tomographic data are used together with field, core and well log structural information to determine the detailed 3-D architecture of fault zones in a granitic massif of volume 500×575×168 m at Mina Ratones area in the Albalá Granitic Pluton. To facilitate the integration of the different data, geostatistical simulation algorithms are applied to interpolate the relatively sparse structural (hard) control data conditioned to abundant but indirect 3-D (soft) seismic tomographic data. To effectively integrate geologic and tomographic data, 3-D migration of the velocity model from the time domain into the depth domain was essential. The resulting 3-D model constitutes an image of the fault zone architecture within the granitic massif that honours hard and soft data and provides an evaluation of the spatial variability of structural heterogeneities based on the computation of 3-D experimental variograms of Fracture Index (fault intensity) data. This probabilistic quantitative 3-D model of spatially heterogeneous fault zones is suitable for subsequent fluid flow simulations. The modeled image of the 3-D fault distribution is consistent with the fault architecture in the Mina Ratones area, which basically consists of two families of subvertical structures with NNE–SSW and ENE–WSW trends that displaces the surfaces of low-angle faults (North Fault) and follows their seismically detected staircase geometry. These brittle structures cut two subvertical dykes (27 and 27′ Dykes) with a NNE–SSW to N–S trend. The faults present high FI (FI>12) adjacent bands of irregular geometry in detail that intersect in space delimiting rhombohedral blocks of relatively less fractured granite (FI<6). Both structural domains likely correspond with the protolith and the damaged zone/fault core in the widely accepted model for fault zone architecture. Therefore, the construction of 3-D grids of the FI in granitic areas affected by brittle tectonics permits the quantitative structural characterization of the rock massif.  相似文献   

Microearthquakes and faulting in the southern Okinawa Trough     

Mamoru Nakamura  Hiroshi Katao 《Tectonophysics》2003,372(3-4):167-177

Southern Okinawa Trough represents an early stage of back-arc rifting and is characterized by normal faulting and microearthquakes. Earthquake distribution and deep structure of fault was investigated to clarify active rifting in the southern Okinawa Trough, where two parallel grabens are located. A network of ocean bottom seismometers (OBSs) that displayed the hypocenters of 105 earthquakes were observed for a period of 4 days in southern-graben (SG). Most of the microearthquakes occurred in a cluster about 7 km wide, which on a cross-section striking N45°E dips 48° to the southwest. Relocated hypocenters, which are recorded by a local seismic network, show scattered distribution around the southern-graben. There are no remarkable surface faults in the southern-graben. On the other hand, the recalculation of hypocenter locations of 1996 earthquakes swarm recorded by a local seismic network suggests that the swarm is associated with normal faulting on the southern side of northern-graben (NG). Thus, the undeveloped southern-graben is located to the south of the developed northern-graben. Southward migration of rifting, which may be caused by migration of volcanism, could thus be occurring in the southern Okinawa Trough. The extension rate computed for the southern Okinawa Trough from the fault model of the northern-graben is 4.6 cm/year, which is 59–102% of the extension rate (GPS measurements). This result indicates that the majority of extensional deformation is concentrated within the center of the northern-graben in the Okinawa Trough.  相似文献   

Coal mining along the Warfield Fault, Mingo County, West Virginia: a tale of ups and downs     

J. Marc Coolen   《International Journal of Coal Geology》2003,54(3-4):193

Mine development along a 15-mile (24 km) section of the Warfield Fault in Mingo County, West Virginia has broadened the geological understanding of the fault and its related structures. The fault has been exposed in two new road cuts, one in the northeast-trending segment at Neely Branch and one in the eastern east-trending segment at the head of Marrowbone Creek. Both exposures show a well-defined normal fault with a 45° to 55° N dip, juxtaposing sandstone/shale packages from the roof and the floor of the Coalburg seam. The fault is associated with a thin gouge zone, some drag folding, and parallel jointing. Its trace tends to run parallel to the crest of the adjacent Warfield Anticline. Based on underground mine development and detailed core drilling, the vertical offset along the fault plane ranges from a maximum of 240 ft (73 m) in the central part of the area near the structural bend to less than 100 ft (30 m) in western and eastern directions. The fault is located along the relatively steeply dipping (locally in excess of 25%) southern limb of the Warfield Anticline, and appears related to a late phase of extension involving folded Pennsylvanian strata. On a regional scale, the lithological variations across the fault do not suggest any appreciable strike-slip component.Underground room and pillar mines in the Coalburg seam north and south of the fault have been greatly impacted by the Warfield structures. Due to the combined (and opposite) effects of the folding and faulting, the northern mines are located up to 400 ft (125 m) higher in elevation than the southern ones. Overland conveyor belts connect mining blocks separated by the fault. The practical mining limit along the steep slopes toward the fault is around 15%. Subsidiary normal faults with offsets in the 5- to 15-ft (1.5–4.5 m) range are fairly common and form major roof control and production hurdles. Overall, the Warfield structures pose an extra challenge to mine development in this part of the Appalachian Coalfields.  相似文献   

Can flat-ramp-flat fault geometry be inferred from fold shape?: A comparison of kinematic and mechanical folds     

Heather M. Savage  Michele L. Cooke 《Journal of Structural Geology》2003,25(12):2023-2034

The inference of fault geometry from suprajacent fold shape relies on consistent and verified forward models of fault-cored folds, e.g. suites of models with differing fault boundary conditions demonstrate the range of possible folding. Results of kinematic (fault-parallel flow) and mechanical (boundary element method) models are compared to ascertain differences in the way the two methods simulate flexure associated with slip along flat-ramp-flat geometry. These differences are assessed by systematically altering fault parameters in each model and observing subsequent changes in the suprajacent fold shapes. Differences between the kinematic and mechanical fault-fold relationships highlight the differences between the methods. Additionally, a laboratory fold is simulated to determine which method might best predict fault parameters from fold shape. Although kinematic folds do not fully capture the three-dimensional nature of geologic folds, mechanical models have non-unique fold-fault relationships. Predicting fault geometry from fold shape is best accomplished by a combination of the two methods.  相似文献   

昆仑山口西8.1级地震前青藏块体边界断层异常活动   总被引：5，自引：0，他引：5  

范燕  车兆宏 《地震》2003,23(2):121-126

系统分析了青藏块体边界断层的形变资料，研究了断层活动的动态过程及空间分布。结果表明，昆仑山口西8．1级地震前孕震影响范围达到青藏块体的周边地区；发震断层所在的构造带震前断层活动最为剧烈；加强对构造块体断层整体活动的宏观动态比较和分析，有助于判定未来强震发生的危险地段；震后应力将转移并集中到西秦岭构造带及其邻近地区。  相似文献