Permafrost environment monitoring on the Qinghai-Tibet Plateau using time series ASAR images

The permafrost in Qinghai-Tibet Plateau (QTP) has long been the focus of many researchers. In this study, we first use the method that integrates synthetic aperture radar (SAR) intensity and phase information to monitor permafrost environment in the Beiluhe Region, using time series advanced SAR images. The backscattering coefficients (σ⁰) and deformation were extracted for the main features, and the influences of meteorological conditions to them were also quantified. The results show that both the change in σ⁰ and surface deformation are closely related to the active layer, and the deformation is also affected by the permafrost table. First, over meadow and sparse vegetation regions, σ⁰ rose about 6.9 and 4 dB from the freezing to thawing period, respectively, which can be mainly attributed to the thaw of the active layer and increased precipitation. Second, seasonal deformation, derived from the freeze-thaw cycle of the active layer, was characteristic of frost heave and thaw settlement and exhibited a negative correlation with air temperature. Its magnitude was larger than 1 cm in a seasonal cycle. Last, significant secular settlement was observed, with rates ranging from –16 to 2 mm/a, and it was primarily due to the thaw of the permafrost table caused by climate warming.     

利用储层饱和度仪双探测器测井资料反演持油率

应用储层饱和度仪（RST）在水平或大斜度的生产井中进行测量,可以取得连续的油、气、水持率测量值。笔者探讨了RST测井求持油率的方法,在RST双探测器测井模型分析的基础上确定井筒持油率。在反演过程中,采用了随机数分析方法获取仪器的灵敏度系数,获得的灵敏度系数较为精确。结合其他测井资料,将所求的系数用于反演模型求取井筒持油率的计算中,通过计算值和实测值的对比及其相关系数分析,证明了该方法的可行性。     

Correlations between global features of terrestrial fields

Studies of correlation coefficients between different sets of global geophysical data may lead to useful inferences concerning their relationship or independence. If one data set is allowed to rotate with respect to another, the statistical theory is complicated and extra care is required before one can conclude that there is any statistical significance to a maximized correlation coefficient. If, for some relative rotation, two spherical harmonic fields are significantly correlated, then their individual degree component harmonics of dominant power must also be significantly correlated. Rotations can be found that result in high correlations between the dominant low-degree spherical harmonics of the geomagnetic and tertestrial gravity field potentials, but rotations can also be found that result in equally high, yet meaningless, correlations if the lunar gravity field is substituted for the geomagnetic field. To explain such high correlations, the theoretical correlation distribution function between normally distributed component harmonics is derived and then verified for lowdegree harmonics by using a Monte Carlo technique which takes into account the three-dimensional rotation group. Some curious properties surface: (1)the correlation distribution function for all possible relative orientations is almost the same between identical and uncorrelated fields; and (2)a system for determining the correlation distribution function from randomly selected fields or from randomly rotated fields is almost ergodic.     

重力异常源深度探讨

对不同深度内异常密度的分布与不同阶次谐波分量间的关系作了两种假设，利用ＧＥＭ１０Ｃ地球模型的２～３６阶球谐系数计算了在这两种假设下不同阶次的球谐系数所对应的异常场源深度。结合已知的地球物理信息讨论了本文计算结果的合理性。     

Reflection of P and SV waves from free surface of an elastic solid with generalized thermodiffusion

The governing equations for generalized thermodiffusion in an elastic solid are solved. There exists three kinds of dilatational waves and a Shear Vertical (SV) wave in a two-dimensional model of the solid. The reflection phenomena of P and SV waves from free surface of an elastic solid with thermodiffusion is considered. The boundary conditions are solved to obtain a system of four non-homogeneous equations for reflection coefficients. These reflection coefficients are found to depend upon the angle of incidence of P and SV waves, thermodiffusion parameters and other material constants. The numerical values of modulus of the reflection coefficients are presented graphically for different values of thermodiffusion parameters. The dimensional velocities of various plane waves are also computed for different material constants.     

Studying the migration behaviour of selenate in Boom Clay by electromigration

For the disposal of high-level waste (HLW) in a deep geological formation as Boom Clay, safety assessment studies have shown that long lived ⁷⁹Se is one of the more critical fission products. Therefore, the knowledge of its migration properties (diffusion, retention) through the geological barrier (Boom Clay) is of paramount importance. The migration behaviour of selenium strongly depends on its speciation. Under reducing conditions, selenide would be the dominant species and selenium migration would mainly be controlled by the low solubility of Se(−II)-bearing minerals. However Se species are often found in redox disequilibrium and more oxidized species might also coexist. Therefore, the study of selenate migration requires attention, as it might be the most mobile selenium species in the host rock. Electromigration experiments performed with a ⁷⁵Se-labeled selenate in Boom Clay indicate a high mobility for this species. The apparent diffusion coefficient (D_app) of selenate in Boom Clay is estimated from electromigration experiments performed under different electric fields. Using two independent approaches, the value of D_app for selenate is shown to fall in the range from 1.7×10⁻¹¹ to 6.2×10⁻¹¹ m² s⁻¹. Moreover, no reduction of selenate in Boom Clay was observed.     

青藏块体东北缘及其周围地区现今时空运动变形科特征

依据非连续变形分析(DDA)方法,考虑特定块体边界不同程度的适度侵入,利用3期GPS观测资料(1991、1999、2001年),建立了青藏块体东北缘及其周围地区的一级块体运动模型和划分较细的、反映较小区域运动变形的较理想块体运动模型.模拟得到了研究区内北西西向大断裂间一级块体的运动变化特征、研究区主应变率场的分布特征及青藏块体北边界断裂的分段非均匀时空运动特征.     

国际参考地磁场模型中高阶球谐项对地磁场长期变化的影响

在国际参考地磁场（IGRF）模型中，高阶球谐系数比低阶系数小得多，所以高阶项对主磁场的贡献常被忽略不计. 但是，高阶项对主磁场的长期变化却有重大影响. 本文根据第八代IGRF模型，分析了IGRF 1945～1955中高阶球谐系数的异常特征对长期变化的影响，然后用修正IGRF模型估计并改正了这些影响. IGRF高阶项随深度增加而迅速增大，所以高阶系数的误差对深部磁场位形和磁场能量的计算有不可忽视的影响，对核幔界面流动状态的推断和地核半径的地磁估计有更为重大的影响.     

基于边界元的非连续(块体系统)形变反分析法

以边界元法按位移解平面应力问题方法为基础，取边界单元的位移和表面力为未知参量，区域上的位移方程为观测方程，区域上测得的位移为观测值，按最小二乘原理，先解出未知参量，然后按位移方程计算区域内的位移，按应力方程计算区域内的应力场。在此基础上，应用非连续形变分析的基本原理，讨论了保证非连续块体系统运动的合理性应附加的应力和运动学约束条件及其表达形式。以及判定块体间相互接触关系状况的方法，以确定是否附加应力和运动学约束。