Asymptotic theory for calculating deformations caused by dislocations buried in a spherical earth: geoid change   总被引：2，自引：0，他引：2  

W. Sun 《Journal of Geodesy》2003,77(7-8):381-387

An asymptotic theory is presented for calculating co-seismic potential and geoid changes, as an approximation of the dislocation theory for a spherical Earth. This theory is given by a closed-form mathematical expression, so that it is mathematically simple and can be applied easily. Moreover, since the asymptotic theory includes sphericity and vertical structure effects, it is physically more reasonable than the flat-Earth theory. A comparison between results calculated by three dislocation theories (the flat-Earth theory, the theory for a spherical Earth and its asymptotic solution) shows that the true co-seismic geoid changes are approximated better by the asymptotic results than by those of a flat Earth. Numerical results indicate that the sphericity effect is obvious large, especially for a tensile source on a vertical fault plane. AcknowledgementsThe author is grateful to Dr S. Okubo for his helpful suggestions and discussions. Comments by anonymous reviewers are also greatly acknowledged. This research was financially supported by JSPS research grants (C13640420) and Basic design and feasibility studies for the future missions for monitoring Earths environment.  相似文献   

Far-Zone Contributions to Topographical Effects in the Stokes-Helmert Method of the Geoid Determination     

Tenzer  R.  Vaníček  P.  Novák  P. 《Studia Geophysica et Geodaetica》2003,47(3):467-480

In the evaluation of the geoid done according to the Stokes-Helmert method, the following topographical effects have to be computed: the direct topographical effect, the primary indirect topographical effect and the secondary indirect topographical effect. These effects have to be computed through integration over the surface of the earth. The integration is usually split into integration over an area immediately adjacent to the point of interest, called the near zone, and the integration over the rest of the world, called the far zone. It has been shown in the papers by Martinec and Vaníek (1994), and by Novák et al. (1999) that the far-zone contributions to the topographical effects are, even for quite extensive near zones, not negligible.Various numerical approaches can be applied to compute the far-zone contributions to topographical effects. A spectral form of solution was employed in the paper by Novák et al. (2001). In the paper by Smith (2002), the one-dimensional Fast Fourier Transform was introduced to solve the problem in the spatial domain. In this paper we use two-dimensional numerical integration. The expressions for the far-zone contributions to topographical effects on potential and on gravitational attraction are described, and numerical values encountered over the territory of Canada are shown in this paper.  相似文献   

Gravity-enhanced representation of measured geoid undulations using equivalent sources     

Fernando Guspí  Antonio Introcaso  Beatriz Introcaso 《Geophysical Journal International》2004,159(1):1-8

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A local geoid determination based on ellipsoid approximation in Western China     

Essam Ghanem 《地球空间信息科学学报》2002,5(3):6-10

A new methodology for precise geoid determination with finest local details based on ellipsoidal approximation is presented.This methodology is formulated through the “fixed-free two-boundary value problem“ based on the observable of the type modulus of gravity intensity,gravity acceleration and gravity potential at the GPS positioned stations,with support of the known geoid‘s potential value,W0.  相似文献   

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

J. Kakkuri  & Z. T. Wang 《Geophysical Journal International》1998,135(2):495-504

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.  相似文献   

Gravity potential at the Major Vertical Datum as primary geodetic constant     

Mariya I. Yurkina 《Studia Geophysica et Geodaetica》1996,40(1):9-13

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).  相似文献   

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   总被引：1，自引：0，他引：1  

杨沾吉  於宗俦  于正林  陈永奇 《武汉大学学报(信息科学版)》1996,(4)

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  相似文献   

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

D. Zhong 《Journal of Geodesy》1997,71(9):552-561

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  相似文献   

Topography and geoid due to lithospheric mass anomalies   总被引：3，自引：0，他引：3  

Yves Le Stunff  Yanick Ricard 《Geophysical Journal International》1995,122(3):982-990

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FFT实现物理大地测量边值问题类型转换     

黄永强 《武汉大学学报(信息科学版)》1989,(4)

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。  相似文献