Gravity Field And Dynamics Of The Earth

Since the Czech edition was published four years ago, the authors have revised the original text tobring it up to date. During these four years, thanks to satellite altimetry the accuracy of the global descrip tion of the gravity field (model GEM-T2), of the fundamental astro geodetic constants, of the principal moments of inertia of the Earth and, in particular, of their differences, of the precession constant, and of a number of other dynamical parameters of the Earth have been improved. The authors have included most of these improvements in the revised English edition. They have, of course, also made factual, formal and other corrections and have modified some of the figures. Additions to the index and references have also been made. Praha, Czech Republic M. BuRSA and K. PF:c August 1993 Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fundamentals of Determining the Parameters 1 Defining the Earth's Gravitational Field by Satellite Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 1 Satellite Equations of Motion . . . . . . . . . . . . . . . . . 6 1. 2 Perturbing Function and Perturbing Potential . . . . 23 1. 3 General Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 23 1. 3. 1 Perturbing Gravitational Potential of the Earth in 1. 3. 2 Outer Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Perturbations due to the Moon and the Sun . . . . . . 27 1. 3. 3 Solution of the Perturbed Motion . . . . . . . . . . . . . . 28 1. 4 1. 5 Transformation of the Perturbing Gravitational Potential into the Function of the Satellite's Orbital Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 1. 5. 1 Transformation of Potential Rs$ . . . . . . . . . . . . . . . 32 1. 5. 2 Transformation of Potentials L1 Vs»' L1 Vso . . . . . . . .

New and more accurate techniques for satellite gravimetry will be available soon, with promising applications in Earth sciences. With this special issue the authors want to stimulate discussion among Earth scientists on objectives and preferences for future satellite gravimetry missions. This is an urgently needed discussion. Visions for follow-on missions have to be developed today, if they are to be realized within 10 years, given the required preparation time of such satellite missions.

In their search for solutions to problems concerning the dynamics of the Earth as a self-gravitating body, the authors have applied the fundamentals found in their book “Jacobi Dynamics” (1987, Reidel). First, satellite observations have shown that the Earth does not remain in hydrostatic equilibrium, which forms the physical basis of modern geodynamics. Secondly, satellite data have established a relationship between the planet’s polar moment of inertia and the potential of the Earth’s outer force field, which proves the most basic point of Jacobi dynamics. This allowed the authors to revise their derivation of the classical virial theorem, introducing the concept of a volumetric force and volumetric moment, and so to obtain a generalized virial theorem in the form of Jacobi’s equation. The main dynamical effects are: the kinetic energy of oscillation of the interacting particles, which explains the physical meaning and nature of gravitational forces; separation of shells of a self-gravitating body with respect to its mass density; differences in angular velocities of the shell’s rotation; continuity in variance of the potential of the outer gravitational force field, together with reductions in the envelope of the interacting masses (volumetric center of gravity); the nature of Earth, Moon and satellite precession; the nature and generating mechanism of the planet’s electromagnetic field; the common nature of gravitational and electromagnetic energy, and other related issues. The work is a logical continuation of the book "Jacobi Dynamics" and is intended for researchers, teachers and students engaged in theoretical and experimental research in various branches of astronomy, geophysics, planetology and cosmogony, and for students of celestial, statistical, quantum and relativistic mechanics and hydrodynamics.

This volume opens up new perspectives on the physics of the Earth’s interior and planetary bodies for graduate students and researchers working in the fields of geophysics, planetary sciences and geodesy. It looks at our planet in an integrated fashion, linking the physics of its interior to geophysical and geodetic techniques that record, over a broad spectrum of spatial wavelengths and time scales, the ongoing modifications in the shape and gravity field of the planet. Basic issues related to the rheological properties of the Earth and to its slow deformation are considered, in both mathematical and physical terms, within the framework of an analytical relaxation theory. Fundamentals of this theory are developed in the first two Chapters. Chapters 3-9 deal with a wide range of applications, ranging from changes in the Earth’s rotation to post-seismic deformation and from sea-level variations induced by post-glacial rebound to tidal deformation of icy moons of the Solar System. This Second Edition improves substantially our formalism implementing compressibility in viscoelastic relaxation. Chapter 5 now contains new developments in the physics of the gravitational effects of large earthquakes at subduction zones, made possible by new gravity data from space missions. The new Chapter 9 of this Second Edition on deformation and stresses of icy moons enlarges the applications of the book to Planetology, dealing with the additional complications in the theory of viscoelastic relaxation introduced by the shallow low-viscosity zones and inviscid water layers of the moons of Jupiter and Saturn.

This volume opens up new perspectives on the physics of the Earth's interior for graduate students and researchers working in the fields of geophysics and geodesy. It looks at our planet in an integrated fashion, linking the physics of its interior to the geophysical and geodetic techniques that record, over a broad spectrum of spatial wavelengths, the ongoing modifications in the shape and gravity field of the planet. Basic issues related to the rheological properties of the Earth's mantle and to its slow deformation will be understood, in both mathematical and physical terms, within the framework of an analytical normal mode relaxation theory. Fundamentals of this theory are developed in the first, tutorial part. The second part deals with a wide range of applications, ranging from changes in the Earth's rotation to post-seismic deformation and sea-level variations induced by post-glacial rebound. In the study of the physics of the Earth's interior, the book bridges the gap between seismology and geodynamics.

International Geophysics Series, Volume 10: The Gravity Field of the Earth: From Classical and Modern Methods explores the theory of the gravity field of the earth based on both classical and modern methods. Classical method involves observations of gravity taken over the earth's surface, while the modern method uses observations of variation of orbital elements of artificial satellites caused by the gravity field of the earth. This book is organized into two parts encompassing 12 chapters. Part I describes the solution of physical problems that are treated as Dirichlet problems or solved by means of integral equations. This part also deals with the determination of the geoid form from ground gravity measurements using the Stokes formula. The method of obtaining the Stokes formula by means of an integral equation is also outlined. Part II contains modern mathematical techniques developed to utilize the observations of artificial satellites for geodetic purposes. This book could be used as a textbook for students in the fields of geodesy, geophysics, or astronomy.

For the past three decades, it has been possible to measure the earth's static gravity from satellites. Such measurements have been used to address many important scientific problems, including the earth's internal structure, and geologically slow processes like mantle convection. In principle, it is possible to resolve the time-varying component of the gravity field by improving the accuracy of satellite gravity measurements. These temporal variations are caused by dynamic processes that change the mass distribution in the earth, oceans, and atmosphere. Acquisition of improved time-varying gravity data would open a new class of important scientific problems to analysis, including crustal motions associated with earthquakes and changes in groundwater levels, ice dynamics, sea-level changes, and atmospheric and oceanic circulation patterns. This book evaluates the potential for using satellite technologies to measure the time-varying component of the gravity field and assess the utility of these data for addressing problems of interest to the earth sciences, natural hazards, and resource communities.