对各向异性介质中横波分裂现象的研究

在本文中，我们系统研究了各向异性介质中的横波分裂现象，探讨了各向异性介质中横波分裂现象产生的机理，并给出了引起各种异性的薄层组合以及裂隙定向分布的数学模型。     

倾斜电各向异性介质大地电磁正演研究

研究地层电各向异性性质能够圈定沉积地层中的油气储层和与地球动力学过程、地震预报有关的深部线性构造。通过得到的N层倾斜电各向异性介质大地电磁响应公式,在不同的电各向异性系数、地层倾角、倾斜层厚度参数下,对电各向异性倾斜地层模型进行了正演计算。结果表明:当电各向异性系数、地层倾角、地层厚度三者中任一变量改变时,视电阻率曲线的形态基本保持不变,但视电阻率曲线振幅值变化较大;视电阻率曲线对地层倾角参数的变化反应最为敏感;电各向异性系数的增加,能突显薄层电阻率异常。这有助于以后的电各向异性介质大地电磁反演和应用研究。     

含倾斜定向排列裂隙介质纵波特征

根据Schoenberg的含裂隙介质的线性滑移模型在弱各向异性近似条件下根据Bond变换获得了含倾斜定向排列裂隙介质的弹性系数矩阵。在将含倾斜定向排列裂隙介质视为倾斜横向各项同性（TTI）介质的基础上根据弱各向异性近似条件下TTI介质纵波相速度、弹性波阻抗以及反射系数的近似解析解,研究了裂隙倾斜角对含倾斜定向排列裂隙介质中纵波相速度、反射系数以及波阻抗的影响。研究发现含倾斜裂隙介质的纵波相速度、各向异性弹性波阻抗、反射系数三个参数具有类似方位各向异性特征：入射角大的时候,显示较强方位各向异性,但是这三个参数对入射角的依赖程度却不完全相同,反射系数对入射角的依赖程度最大。     

裂缝诱导双相HTI介质模型及其弹性波传播方程

将Biot双相介质理论与Gurevich裂缝各向异性理论相结合,建立了能够同时考虑实际裂缝性储层孔隙性和各向异性的裂缝诱导双相HTI介质模型。从本构方程、动力学方程和动力学达西定律出发,推导出了裂缝诱导双相HTI介质中弹性波传播的一阶速度-应力方程,并针对方程的刚性问题,给出了利用显式二阶时间积分法数值求解该方程时所需要满足的稳定性条件。该方程能够定量地给出双相HTI介质的波场特征与裂缝参数、背景孔隙介质参数之间的关系,描述弹性波在这种介质中的传播机理。     

黏弹性和速度各向异性对薄层反射的影响

煤层具有强波阻抗差、低阻抗的特性,对地震勘探来说是一种典型的薄层。因为其黏弹性和速度各向异性导致薄层反射波场异常,为了定量分析黏弹性和速度各向异性对薄层地震反射的影响,针对强波阻抗差薄层模型,基于波动方程数值模拟方法,正演得到弹性速度各向同性、黏弹性速度各向同性及黏弹性速度各向异性的地震波场,并对比分析了3种模型的弹性波地震反射特征。研究结果表明:黏弹性对薄层的反射产生不可忽略的影响,会明显降低薄层弹性波的反射振幅,但黏弹性速度各向同性与各向异性对薄层的弹性波反射影响差异不大。相比于弹性各向同性情况,黏弹性会引起反射纵波（PP波）瞬时频率最大可达8%的改变量,而对转换横波（PS波）仅有3%的改变量,可以忽略不计。上述研究为利用构造煤品质因子极低的特征来预测构造煤提供了可能。      

各向异性介质储层数值模拟及波场特征研究

各向异性介质储层中波场特征的研究,有利于对多波资料的准确解释。在弹性波方程基础上,结合数值模拟技术与AVO技术,对多种介质模型和第二类含气砂岩储层模型进行数值模拟与波场特征描述。以表征介质各向异性程度的Thomsen参数为出发点,研究各参数对地震波场动力学和运动学特征的影响,并对第二类含气砂岩介质中模拟得到的正演记录,以及各向异性参数对波场的影响程度进行分析,进一步加深了对该类储层各向异性特征的认识,这为各向异性介质中的参数反演与地震资料解释提供了有力的参考依据。     

基于各向异性AVO的裂缝弹性参数叠前反演方法

基于各向异性理论,将具有水平对称轴的高角度裂缝介质等效为HTI介质。首先,通过分析HTI介质反射界面的纵波反射系数公式,研究裂缝介质振幅随偏移距和方位角的变化特征,探索了方位各向异性介质弹性参数和各向异性参数的叠前反演方法。其次,为更好地估测介质的弹性参数:纵波阻抗IP、横波阻抗IS以及各向异性梯度Γ,对反射系数近似式进行了简化,同时对简化公式的精度进行了对比分析。最后,选取2D逆掩断层模型,利用褶积公式制作不同方位的合成地震道集,并对合成地震道集添加随机噪声(信噪比为2∶1),将其应用于方位AVO叠前反演算法试算中。结果表明,当信噪比为2时,方位AVO叠前反演所得纵波阻抗、横波阻抗及各向异性梯度的估测值与模型真实值基本吻合,而且估测值能够较准确地反映原始模型的地层特征,验证了方位AVO叠前反演算法的准确适用性。     

裂隙介质弹性性质研究

波在介质中传播，主要是受介质的弹性性质的影响，在各向同性的岩石背景上，含有裂隙；岩石表现为各向异性，裂隙的形状不同，各向异性的性质也不同。本文在Hudson模型基础上，应用散射理论，研究了垂直定向分布的裂隙介质（EDA），水平分布的裂隙介质（PTL）、正交裂隙介质（ORA）、两组垂直斜交的裂隙介质（EDA＋EDA）等4种类型裂隙介质的弹性性质，给出弹性参数计算公式，并分析了裂隙介质与各向异性之间的内在联系。     

井地联合提取VTI介质各向异性参数

在新疆塔里木盆地某地区的宽方位三维地震数据中,VTI介质火成岩的各向异性和垂向速度变化引起非双曲线时差。通过对实际资料的系统分析,我们不能利用DMO反演法,移动震源VSP反演法和多偏移距VSP初至旅行时反演法提取Thomsen参数用于各向异性地震资料的处理。因此本文提出一个新的方法:运用地震资料和零偏移距VSP井求取火成岩的各向异性参数δ;在比较精确确定火成岩地层深度和厚度的情况下,利用偏移距VSP井,求取了各向异性参数ε,从而获得火成岩的瞬时各向异性参数η;充分考虑VTI介质垂向速度变化对时差曲线的影响,获得了各向异性参数ηeff。最后,利用所提取的各向异性参数,进行VTI介质各向异性速度分析和成像,成像质量得到明显改善。     

VTI介质瑞雷波频散曲线特征与对比分析

在近地表瑞雷波勘探中,介质的各向异性对瑞雷波传播有着明显的影响。为了研究横向各向同性(vertical transverse isotropy,简称VTI)介质各向异性参数对瑞雷波的影响,以各向异性弹性波理论为基础,利用应力镜像法为边界条件,实现了VTI介质中瑞雷波的正演数值模拟,并利用相移法提取瑞雷波频散曲线。将层状各向同性介质和VTI介质瑞雷波频散曲线作对比,研究结果表明:(1)瑞雷波各阶模式相速度随纵波变异系数δ的增大而减小,随纵波各向异性强度参数ε的增大而增大;(2)随着纵波各向异性强度参数ε的减小和纵波变异系数δ的增大,会引起瑞雷波各阶模式相速度减小和瑞雷波频散曲线各阶模式主要能量所在频带范围减小;(3)当纵波各向异性强度参数ε减小和纵波变异系数δ增大到一定程度后,在速度递增的层状介质中会引起瑞雷波出现"之"字形频散曲线,在含软弱夹层的层状介质中会出现各阶模式频散曲线混淆的现象。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861