Group Time Delay in the Reflection of P-Polarized Electromagnetic Plane Waves at a Stratigraphic Interface

The group time delay (GTD) formulae of quasi-total reflection of inhomogeneous P-polarized electromagnetic waves (P-PEW, whose electric field parallels to the plane of incidence), caused by the Goos–Hänchen effect, is derived by the phase shift of the wave. A numerical example where the frequency equals to 1 GHz is given. The curves of calculating results show that there are three discontinuous points at the critical angle of phase shift vector, the critical angle of attenuation vector and 90^○. When the angle of incidence is equal to one of these three angles, the GTD will become infinite, and the electromagnetic wave will propagate along the interface. The GTD will be very large, when the angle of incidence is close to one of these three angles. The results indicate that there is an important relationship between the two critical angles and the conductivity and permittivity of the two strata, and that the GTD has an important relationship with the angle of incidence. These results can be used to determine the lithology of the strata and to delimit the interfaces of strata more effectively. It is suggested that this research may prove useful in electromagnetic logging analysis and, perhaps, in the design of logging instruments.     

实际井眼条件下过套管电阻率测井响应的传输线方程正演算法

过套管电阻率测井通过测量套管壁电势实现测量地层视电阻率,不同的地层模型对过套管电阻率测井会有不同的测井响应. 在传输线方程系数中本文考虑了径向含多个界面地层的影响,对轴向（井轴方向）呈层状、径向阶跃变化地层模型,给出了电势分布递推公式,计算了过套管电阻率测井响应,绘出了测井响应曲线. 算例表明,该方法有较强的轴向地层界面分辨能力;对径向均匀地层计算结果非常接近地层模型电导率,能较好地反映实际地层特征;对高电导地层,低电导水泥环有明显的测井响应;当径向存在多个地层界面时计算结果则为径向各层电导率的综合反映,不是某一径向层的电导率;算例显示该方法有较快（算例运行时间在1s内）的计算速度.     

An Accurate Method of Computing the Gradient of Seismic Wave Reflection Coefficients (SWRCs) for the Inversion of Stratum Parameters

The optimization inversion method based on derivatives is an important inversion technique in seismic data processing, where the key problem is how to compute the Jacobian matrix. The computational precision of the Jacobian matrix directly influences the success of the optimization inversion method. Currently, most of the AVO (amplitude versus offset) inversions are based on approximate expressions for the Zoeppritz equations to obtain the derivatives of the seismic wave reflection coefficients (SWRCs) with respect to the stratum parameters. As a result, the computational precision and range of applications of these AVO inversions are restricted undesirably. In order to improve the computational precision and to extend the range of applications of AVO inversions, the partial derivative equations of the Zoeppritz equations are established, with respect to the ratios of wave velocities and medium densities. By solving the partial derivative equations of the Zoeppritz equations accurately, we obtained the partial derivative of SWRCs with respect to the ratios of seismic wave velocities and medium densities. With the help of the chain rule for derivatives, the gradient of the SWRCs can be accurately computed. To better understand the behavior of the gradient of the SWRCs, we plotted the partial derivative curves of the SWRCs, analyzed the characteristics of these curves, and gained some new insight into the derivatives. Because only a linear system of equations is solved in our method without adding any new restrictions, the new computational method has both high precision and a quick running speed; it is not only suitable for small incident angles and weak reflection seismic waves but also for large incident angles and strong reflection seismic waves. With the theoretical foundations established in the article, we can further study inversion problems for layered stratum structures and we can further improve the computational speed and precision of the inversions.     

介质密度反演偏导矩阵的精确计算方法

实现反演偏导矩阵的计算是基于导数最优化反演方法的关键,然而目前的地震反演几乎都是基于Zoeppritz方程近似实现的,使计算精度和适应范围受到限制.本文利用Zoeppritz方程建立了反射系数对地层介质密度比偏导方程,导出了Zoeppritz方程矩阵元对介质密度比的导数.通过求解偏导方程获得了反射系数对介质密度比偏导数的精确计算(考虑了速度中含介质密度的问题).利用数值算例分析了反射系数对介质密度比偏导数的变化特点.本文采用直接解法求解偏导矩阵方程组,获得了快的计算速度和高的计算精度,为实现地层介质密度反演(包括大角度反演)提供了偏导矩阵的计算方法.     

非均匀套管井中的过套管电阻率测井响应

套管井壁的电势分布包含了金属套管和地层模型的信息,套管电阻率的变化对过套管电阻率测井有重要影响,本文考虑了套管电阻率的变化对传输线方程系数的影响,给出了非均匀套管壁电势分布的计算方法．利用套管井壁电势分布实现了非均匀套管测井响应的计算,考察了套管电阻率变化对过套管电阻率测井响应的影响,模拟结果表明,套管的变薄或变厚对测井响应均有一定影响,当套管电阻突然变小（套管变厚）或突然变大（套管变薄）时过套管电阻率测井异常发生在套管电阻突变界面附近．模拟结果还显示电极距对测井结果有明显影响．     

Chronology and geochemistry of Mesozoic granitoids in the Bengbu area,central China: Constraints on the tectonic evolution of the eastern North China Craton

We performed zircon U–Pb dating and analyses of major and trace elements, and Sr–Nd–Pb isotopes for granitoids in the Bengbu area, central China, with the aim of constraining the magma sources and tectonic evolution of the eastern North China Craton (NCC). The analyzed zircons show typical fine-scale oscillatory zoning, indicating a magmatic origin. Zircon U–Pb dating reveals granitoids of two ages: Late Jurassic and Early Cretaceous (²⁰⁶Pb/²³⁸U ages of 160 Ma and 130–110 Ma, respectively). The Late Jurassic rocks (Jingshan intrusion) consist of biotite-syenogranite, whereas the Early Cretaceous rocks (Huaiguang, Xilushan, Nushan, and Caoshan intrusions) are granodiorite, syenogranite, and monzogranite. The Late Jurassic biotite-syenogranites and Early Cretaceous granitoids have the following common geochemical characteristics: SiO₂ = 70.35–74.56 wt.%, K₂O/Na₂O = 0.66–1.27 (mainly < 1.0), and A/CNK = 0.96–1.06, similar to I-type granite. The examined rocks are characterized by enrichment in light rare earth elements, large ion lithophile elements, and U; depletion in heavy rare earth elements, Nb, and Ta; and high initial ⁸⁷Sr/⁸⁶Sr ratios (0.7081–0.7110) and low ε_Nd (t) values (? 14.40 to ? 22.77), indicating a crustal origin.The occurrence of Neoproterozoic magmatic zircons (850 Ma) and inherited early Mesozoic (208–228 Ma) metamorphic zircons within the Late Jurassic biotite-syenogranites, together with the occurrence of Neoproterozoic magmatic zircons (657 and 759 Ma) and inherited early Mesozoic (206–231 Ma) metamorphic zircons within the Early Cretaceous Nushan and Xilushan granitoids, suggests that the primary magmas were derived from partial melting of the Yangtze Craton (YC) basement. In contrast, the occurrence of Paleoproterozoic and Paleoarchean inherited zircons within the Huaiguang granitoids indicates that their primary magmas mainly originated from partial melting of the NCC basement. The occurrence of YC basement within the lower continental crust of the eastern NCC indicates that the YC was subducted to the northwest beneath the NCC, along the Tan-Lu fault zone, during the early Mesozoic.     

非均匀电磁波在导电媒质界面反射的横向偏移

由电磁场边值关系给出了非均匀电磁波在导电媒质界面反射时反射系数所产生的附加相角. 利用这一附加相角导出了非均匀电磁波在导电介质界面的横向偏移,并进行了横向偏移的相关计算,绘出了横向偏移随入射角的变化曲线. 结果表明：在导电媒质界面反射电磁波的横向偏移随入射角的增大而增大,当入射角接近90°时,电磁波在界面要传播较长时间后才返回第一种媒质. 在同一入射角电场偏振化方向在入射面的电磁波要比电场偏振化方向垂直于入射面的电磁波的横向偏移大,随着电磁波频率的增加横向偏移变小.     

Steady flow-induced instability of a partially embedded pipeline: Pipe-soil interaction mechanism

The steady flow-induced instability of a partially embedded pipeline involves a complex process of pipe-soil interaction. In accordance with the hydrodynamic loading and the dimensionless analyses, a series of pipe-soil interaction tests have been conducted with an updated pipe-soil interaction facility including a load-displacement synchronous measurement system, to reveal the underlying pipe-soil interaction mechanism. The effects of pipe surface roughness, end-constraint and initial embedment are investigated, respectively. The values of lateral-soil-resistance coefficient for the rough pipes are bigger than those for the smooth pipes. For a fixed value of non-dimensional submerged weight, the values of lateral-soil-resistance coefficient for the anti-rolling pipes are much larger than those for the freely laid pipes. The effects of initial embedment on the ultimate soil resistance get less with the decrease of the submerged weight of the pipe. A comparison is made between the results of the present mechanical-actuator tests and those of the previous water-flume tests, indicating that those results are quite comparable. For the equivalent level of dimensionless submerged weight, the directly laid pipe in currents has higher lateral stability than in waves.     

平均热点参考基准的建立和岩石圈西向漂移的研究

对于大地测量应用来说,目前IERS机构在定义地球参考系时推荐采用岩石圈无整体旋转(No-Net-Rotation-NNR)约束条件,然而对于地球物理应用来说,相对于NNR参考基准的绝对板块运动数据可能会对地幔对流等研究结果产生误导.考虑到热点的运动,提出建立平均热点(MHS-Medial HotSpot)参考基准的方法,给出建立该基准的约束准则,分别以地学模型NNR-NUVEL1A和实测模型ITRF2005VEL为基础,建立了平均热点参考基准MHS-NUVEL1A和MHS-ITRF2005,并与其它基于热点的绝对板块运动模型进行了比较和分析;讨论了岩石圈的西向漂移,给出了岩石圈相对于下地幔整体旋转的更精确的定量估计,即基于实测的热点参考架MHS-ITRF2005和地学模型NNR-NUVEL1A之间的整体旋转为0.26°/Ma,旋转极在(50°S, 62°E),这与由板块的受力模型给出的岩石圈的整体旋转的旋转极很接近,旋转速率大致快了10%.     

辽源建安—个新的晚白垩世火山群的确定

在辽源建安火山群内运用全岩K-Ar测年方法首次获得老道山、双山、毛山及四甲山火山锥体玄武岩的年龄分别为(99.28±1.59)Ma、(91.70±1.67)Ma、(82.55±1.94)Ma、(82.18±2.37)Ma,可确认建安火山群是当前中国东北乃至中国东部规模最大的晚白垩世火山群。这一结果为探讨中国东部晚白垩世时期的构造演化提供了精确的年代学资料,同时,该火山群的形成与寻找无机成因的油气藏具有重要联系,也为该地区蓝宝石矿及伴生宝石矿的初查工作提供了依据。