夹层厚度对瑞利面波频散曲线的影响     

李业君  张玉池  温佩琳  张兆京 《矿产与地质》2008,22(5):470-472

文章以弹性波横波速度为参数,利用瑞利面波频散曲线的快速标量传递算法进行正演模拟计算,系统研究软弱层厚度对瑞利面波基阶模频散曲线的影响,分析和总结了频率与相速度（f-c）、频率与波数（f-k）、深度与相速度（h-c）等瑞利面波基阶模曲线随软弱层厚度变化的规律。  相似文献   

地壳的拆离作用与华北克拉通破坏:晚中生代伸展构造约束   总被引：19，自引：0，他引：19  

刘俊来  Gregory A.Davis  纪沫  关会梅  白相东 《地学前缘》2008,15(3):72-81

伸展条件下的地壳拆离作用是岩石圈减薄的重要浅部构造响应。晚中生代时期的伸展构造(包括拆离断层、变质核杂岩构造和断陷盆地)在华北、华南、东北和东蒙古及贝加尔地区普遍发育,它们切过上部地壳(断陷盆地)、中、上地壳(拆离断层)或中部地壳(变质核杂岩)。地壳拆离作用具有运动学极性(NWW或SEE)、几何学宏观(区域)对称与微观(局部)不对称性、遍布全区但不均匀性,以及形成时间的跨越性(140~60Ma)等特点,并使得地壳和岩石圈发生显著的减薄。本文研究揭示出现今岩石圈厚度变化与晚中生代伸展构造的发育程度和分布之间并没有必然的联系。其变化的基本规律是,除新生代裂陷发育区岩石圈厚度明显较小且厚度有迅速变化外,从华北向贝加尔地区总体的变化趋势是逐渐加厚,也即东亚地区岩石圈具有楔形形态。晚中生代时期的地壳(或地幔)拆离作用伴随着广泛的岩石圈减薄作用,区域岩石圈同时遭受到一定程度的减薄和破坏,华北克拉通在这一时期的破坏仅仅是区域岩石圈减薄在华北的具体体现。  相似文献   

描述岩石粘弹性固体性质的开尔文模型   总被引：1，自引：0，他引：1  

刘瑞珣  张秉良  张臣 《地学前缘》2008,15(3):221-225

大多数固体材料都具有弹性,但真实的固体却极少严格遵从弹性的虎克定律。这些固体材料的变形往往有对时间的依赖性,这种性质是流变学研究的内容。岩石是自然界最普遍的固体,它的力学性质在通常条件下可用虎克定律作精确的描述,而在漫长的地质过程中,岩石的流变特征就逐渐显现出来。地质作用越缓慢,岩石对变形时间的依赖性越明显。为精确描述岩石在地质过程的力学性质,流变学方法被引入地质学。笔者已经介绍过描述"牛顿流体"的马克斯威尔流变模型,文中介绍描述粘弹性固体的开尔文流变模型。和马克斯威尔模型一样,开尔文模型也是流变学的基本模型,它是由一个弹性元件和一个阻尼元件并联而成。文中给出开尔文模型的本构关系和地质应用的简介。  相似文献   

Surface renewal analysis for sensible and latent heat flux density   总被引：1，自引：1，他引：0  

R. L. Snyder  D. Spano  K. T. Pawu 《Boundary-Layer Meteorology》1996,77(3-4):249-266

High frequency temperature measurements were recorded at five heights and surface renewal (SR) analysis was used to estimate sensible heat flux density (H) over 0.1 m tall grass. Traces of the temperature data showed ramp-like structures, and the mean amplitude and duration of these ramps were used to calculate H using structure functions. Data were compared with H values measured with a sonic anemometer. Latent heat flux density (E) was calculated using an energy balance and the results were compared with E computed from the sonic anemometer data. SR analysis provided good estimates of H for data recorded at all heights but the canopy top and at the highest measurement level, which was above the fully adjusted boundary layer.  相似文献   

饱和软土压缩曲线的“反常”现象     

冯铭璋  王兴涛 《上海国土资源》1990,(3):30-37

饱和软土压缩试验时,经常出现压缩曲线“反常”、压缩系数“倒大”的现象。它是土的原始结构发生破坏前后的不同压缩性的客观反映。饱和软土的结构力很微弱,唯质量好的原状土才能见到这种“反常”。应从成孔、取样、测试及资料整理等多个环节保证其工程意义。  相似文献   

Early Jurassic rift structures associated with the Soapaga and Boyacá faults of the Eastern Cordillera, Colombia: Sedimentological inferences and regional implications     

Andreas Kammer  Javier Snchez 《Journal of South American Earth Sciences》2006,21(4):412

The NW-trending Bucaramanga fault links, at its southern termination, with the Soapaga and Boyacá faults, which by their NW trend define an ample horsetail structure. As a result of their Neogene reactivation as reverse faults, they bound fault-related anticlines that expose the sedimentary fill of two Early Jurassic rift basins. These sediments exhibit the wedge-like geometry of rift fills related to west-facing normal faults. Their structural setting was controlled further by segmentation of the bounding faults at approximately 10 km intervals, in which each segment is separated by a transverse basement high. Isopach contours and different facies associations suggest these transverse anticlines may have separated depocenters of their adjacent subbasins, which were shaped by a slightly different subsidence history and thereby decoupled. The basin fill of the relatively narrow basin associated with the Soapaga fault is dominated by fanglomeratic successions organized in two coarsening-upward cycles. In the larger basin linked to the Boyacá fault, the sedimentary fill consists of two coarsening-upward sequences that, when fully developed, vary from floodplain to alluvial fan deposits. These Early Jurassic rift fills temporally constrain the evolution of the Bucaramanga fault, which accommodated right-lateral displacement during the early Mesozoic rift event.  相似文献   

The origin of the Pedra Furada sandstone tubular structures (South of Lisbon, Portugal)     

T.M. Azevêdo  M.M. Abreu  M. Azevedo Coutinho  J. Figueiras 《Geomorphology》2006,82(3-4):245-254

The Pedra Furada is a 12 m wide, 18 m high outcrop feature showing hundreds of ferruginised sandy tubes and looking in part like a giant organ. In this paper the origin of the tubes is explained on the basis of geochemical, petrographic and microscopic (optical and electronic) analytical data. The tubes are considered to represent vertical escape channels for overpressured water, exhibiting inward decreasing grain size due to water velocity gradients inside the escape channels. The ferruginisation is due to iron oxides associated with colloidal/clayey fine sediments and to goethite formed from solution. The overpressure of water may be due to seismically fluidised beds below the Pedra Furada outcrop or to artesian water ascent. In both cases, fault rupturing may have played a major role in the focussing of the ascending flow.  相似文献   

Crustal structure across the Grand Banks–Newfoundland Basin Continental Margin – II. Results from a seismic reflection profile     

K. W. Helen Lau  Keith E. Louden  Sharon Deemer  Jeremy Hall  John R. Hopper  Brian E. Tucholke  W. Steven Holbrook  Hans Christian Larsen † 《Geophysical Journal International》2006,167(1):157-170

New multichannel seismic reflection data were collected over a 565 km transect covering the non-volcanic rifted margin of the central eastern Grand Banks and the Newfoundland Basin in the northwestern Atlantic. Three major crustal zones are interpreted from west to east over the seaward 350 km of the profile: (1) continental crust; (2) transitional basement and (3) oceanic crust. Continental crust thins over a wide zone (∼160 km) by forming a large rift basin (Carson Basin) and seaward fault block, together with a series of smaller fault blocks eastwards beneath the Salar and Newfoundland basins. Analysis of selected previous reflection profiles (Lithoprobe 85-4, 85-2 and Conrad NB-1) indicates that prominent landward-dipping reflections observed under the continental slope are a regional phenomenon. They define the landward edge of a deep serpentinized mantle layer, which underlies both extended continental crust and transitional basement. The 80-km-wide transitional basement is defined landwards by a basement high that may consist of serpentinized peridotite and seawards by a pair of basement highs of unknown crustal origin. Flat and unreflective transitional basement most likely is exhumed, serpentinized mantle, although our results do not exclude the possibility of anomalously thinned oceanic crust. A Moho reflection below interpreted oceanic crust is first observed landwards of magnetic anomaly M4, 230 km from the shelf break. Extrapolation of ages from chron M0 to the edge of interpreted oceanic crust suggests that the onset of seafloor spreading was ∼138 Ma (Valanginian) in the south (southern Newfoundland Basin) to ∼125 Ma (Barremian–Aptian boundary) in the north (Flemish Cap), comparable to those proposed for the conjugate margins.  相似文献   

生物去除地下水中硫酸盐的实验研究   总被引：1，自引：0，他引：1  

张宏涛  翟辉 《地下水》2005,27(1):19-22

使用平皿夹层厌氧法分离得到纯化的硫酸盐还原菌,通过对比封口、敞口两种情况下细菌培养过程中产生的现象和细菌的生长曲线,表明SRB并非严格的厌氧菌,能耐受一定浓度的环境溶解氧.将该菌用于去除溶液中的SO42-,发现SRB在还原SO42-的过程中,随着SO42-去除率的增加,溶液的pH值会减小,而当SO42-去除率降低时,溶液的pH有增加的趋势;COD/SO42-比值对SO42-的去除率有很重要的影响,在封口情况下,COD/SO42-=0.75时SO42-的最大去除率约为48.60%,COD/SO42比值增加至2.5时,SO42-最大去除率可以达到89.72%,要达到SO42-高去除率,必须增加COD/SO42-比值.  相似文献   

Townsend's Hypothesis, Coherent Structures And Monin–Obukhov Similarity     

K. G. McNaughton  Yves Brunet 《Boundary-Layer Meteorology》2002,102(2):161-175

Townsend's hypothesis states that turbulence near a wall can be divided into an activepart that transports momentum, and an inactive part that does not, and that these twokinds of turbulence do not interact. Active turbulence is generated by wind shear and has properties that scale on local parameters of the flow, while inactive turbulence isthe product of energetic processes remote from the surface and scales on outer-layerparameters. Both kinds of motion can be observed in the atmospheric surface layer, soMonin–Obukhov similarity theory, which is framed in terms of local parameters only,can apply only to active motions. If Townsend's hypothesis were wrong, so that activeand inactive motions do interact in some significant way, then transport processes nearthe ground would be sensitive to outer-layer parameters such as boundary-layer depth,and Monin–Obukhov theory would fail.Experimental results have shown that heat transport near the ground does depend onprocesses in the outer layer. We propose a mechanism for this whereby inactive motionsinitiate active, coherent ejection/sweep structures that carry much of the momentum andheat. We give evidence that the inactive motions take the form of streak patterns of fasterand slower air, and argue that these are induced by the pressure effects of large eddiespassing overhead. The streak pattern includes regions where faster streams of air overtakeand engulf slower-moving streaks. Transverse vortices form across the spines of the streaksat these places and some of them develop into horseshoe vortices. These horseshoe vorticesgrow rapidly and are rotated forward in the sheared flow so they soon contact the ground,squirting the air confined between the legs of the horseshoe vortex outwards as a forcefulejection. This model is consistent with a wide range of results from the field and laboratoryexperiments. Heat transport is significantly affected, so undermining the dimensionalassumptions of Monin–Obukhov similarity theory.  相似文献