Structural effects of the crust on the geoid modelled using deep seismic sounding interpretations

According to the theory of isostasy, the Earth has a tendency to deform its surface in order to reach an equilibrium state. The land-uplift phenomenon in the area of the Fennoscandian Shield is thought to be a process of this kind. The geoid, as an equipotential surface of the Earth's gravity field, contains information on how much the Earth's surface departs from the equilibrium state. In order to study the isostatic process through geoidal undulations, the structural effects of the crust on the geoid have to be investigated.
  The structure of the crust of the Fennoscandian Shield has been extensively explored by means of deep seismic sounding (DSS). The data obtained from DSS are used to construct a 3-D seismic-velocity structure model of the area's crust. The velocity model is converted to a 3-D density model using the empirical relationship that holds between seismic velocities and crustal mass densities. Structural effects are then estimated from the 3-D density model.
  The structural effects computed from the crustal model show that the mass deficiency of the crust in Fennoscandia has caused a geoidal depression twice as deep as that observed from the gravimetric geoid. It proves again that the crust has been isostatically compensated by the upper mantle. In other words, an anomalously high-density upper mantle must exist beneath Fennoscandia.     

Gravity potential at the Major Vertical Datum as primary geodetic constant

Summary On the basis of the fundamental relations of the Molodensky's Earth's figure theory (1945), admitting the inequality of the gravity potentials at the Major Vertical Datum W₀ and on the surface of the reference level ellipsoid U₀, and taken into account that potential W₀ enters into equations directly, it is recomended, W₀ should be adopted as a primary geodetic constant. Parameters of the best fitting ellipsoid are not needed for the solution of geodetic problems and for the investigation of the Earth's gravity field. The reason for requiring the reference and actual fields be close is only that the boundary-value problem can be solved in the linear approximation. Dedicated to the Memory of M.S. Molodensky Contribution to the I.A.G. Special Commission SC3 Fundamental Constants (SCFC).     

中国岩土工程文献数据库的建立与应用

介绍了岩土工程文献数据库的特点，ＭｉｃｒｏＩＳＴＩＣ／ＩＳＩＳ软件的应用与开发，数据库的检索及其应用情况。     

GPS水准、天文重力水准与重力大地水准面多种数据联合处理的研究

针对我国大地水准面的研究状况，提出了在国家ＧＰＳＢ级网完成之后，利用ＧＰＳ水准、天文重力水准与重力大地水准面３类数据确定我国高精度大地水准面的理论和方法。分析了３类数据的误差传播规律，给出了联合平差模型，并用一模拟网进行了试算     

Robust estimation and optimal selection of polynomial parameters for the interpolation of GPS geoid heights

The polynomial interpolation of least squares and interpolation moving least squares based on control stations with known GPS (global positioning system) ellipsoidal heights and levelling orthometric heights are the most often used methods for the interpolation of the geoid heights. But in their applications there occur two problems: one lies in selecting the suitable polynomial parameters; the other in reducing the influences of some possibly abnormal data points. To solve both of the problems, without emphasizing a sound theoretical basis, a heuristic solution with the help of robust estimation technique and optimization criteria for the regression equation is presented. Through two actual numerical examples it is shown that the new solution concept is efficient and can be realized easily on computers. Received: 23 May 1996 / Accepted: 27 March 1997     

FFT实现物理大地测量边值问题类型转换

本文讨论了用快速付里叶变换(FFT)由大地水准面高度数据反算重力异常数据,由此提出了用FFT实现物理大地测量过值问题类型转换这一思想,并与正交基函数法进行了比较,从而得出运用FFT这一方法能达到简化边值问题本身和运算步骤以及节省计算时间的目的。     

关于重力大地水准面精度的探讨

从移去恢复法原理以及局部大地水准面精化残差拟合两个角度,分别得到了重力大地水准面精度估计的直接法与间接法,并通过实例分析了两种方法的误差评定结果。     

模拟大地水准面应用于GPS水准内插的研究

采用移去-恢复技术和多面函数法对已知GPS水准数据进行了内插处理。试验结果表明．利用实际地球物理资料得到的模拟大地水准面精度最高。     

中国海域大地水准面和重力异常的确定

从莫洛金斯基(Molodensky)等1960年给出的由垂线偏差计算大地水准面空域积分公式出发,导出了其相应谱域1维严密卷积和2维球面及平面卷积公式。由Topex/Poseidon,ERS 1/2及Geosat/GM,ERM测高资料求解的垂线偏差计算了我国海域及其邻区大地水准面,其中计算格网为2.5′×2.5′。为了检核,将测高垂线偏差由逆维宁 迈尼兹(Vening Meinesz)公式反演重力异常,与海上船测重力值进行了外部检核;同时还利用司托克斯(Stokes)公式,由上述反演的重力异常计算大地水准面高,与莫洛金斯基公式直接解得的相应结果进行比较作为内部检核。前者的中误差为±9mGal(1Gal=1cm/s2),后者为±0.025m。本文在积分计算中充分应用了2维平面坐标形式和1维卷积严格公式,并做了比较和自校核。