Gravity Field Theory

The gravity method is a nondestructive geophysical technique that measures differences in the earth's gravitational field at specific locations. It has found numerous applications in engineering and environmental studies including locating voids and karst features, buried stream valleys, water table levels and the determination of soil layer thickness. The success of the gravity method depends on the different earth materials having different bulk densities (mass) that produce variations in the measured gravitational field. These variations can then be interpreted by a variety of analytical and computers methods to determine the depth, geometry and density the causes the gravity field variations.

2007

Gravity is a potential field, i.e., it is a force that acts at a distance. The gravity method is a non-destructive geophysical technique that measures differences in the earth‟s gravitational field at specific locations. It has found numerous applications in engineering, environmental and geothermal studies including locating voids, faults, buried stream valleys, water table levels and geothermal heat sources. The success of the gravity method depends on the different earth materials having different bulk densities (mass) that produce variations in the measured gravitational field. These variations can then be interpreted by a variety of analytical and computers methods to determine the depth, geometry and density that causes the gravity field variations. For better definition of the bodies causing the perturbations in the gravity field, the gravity data should be collected with small stations spacing, such as 1 km. For engineering investigations this may be as low as 5 meters or le...

Book, 2014

This book is written mainly for university students taking a course on gravity as one of the methods used in geophysical exploration. It is designed to be an introductory text book that deals with the basic concepts underlying the application of the Earth gravitational field in the exploration of the subsurface geological changes and in prospecting of petroleum and other mineral deposits. As it is familiar with the exploration geophysicists, this subject is fully dealt with in many original authentic internationally-known text books. In this publication, no new subjects were added to those found in the other standard books which are well known in the geophysical library. In fact these and other related scientific papers and research reports formed the solid references for the present work. There is, however, a difference in the design and presentation approach. The essential publications, used as references, are listed at the end of the book. The main feature of this work is being concise and logically sequenced. The objective was to present the subject in a simple and clear way avoiding excessive descriptions and unnecessary lengthy comments. For this reason the text was provided with numerous illustration figures for extra clarification. The book consists of twelve chapters. The first five chapters cover the theoretical aspect of the subject including the gravitational attraction, shape of the planet Earth and nature of the gravity variations, which forms the basis for the exploration capability of the method. The following five chapters deal with measuring instruments, field surveying techniques, data processing, concept of the gravity anomaly and interpretation. A closely associated with gravity anomaly is the phenomenon of isostasy. This was presented in chapter 10. Some modern aspects of the method were covered in chapter 11 and in the last chapter 12 actual gravity field-surveys were reviewed. The first case history is an actual field survey conducted by one of the authors (Hamid Alsadi) in the south-west England in 1965-1966 and the others (by Zuhair Al-Sheikh and Ezzadin N. Baban) were carried out in Iraqi territories. These are included here to serve the purpose of showing how a real gravity surveying is carried out in practice under actual field and processing environments. As always in any publication material, there is always a room for improvement if extra time and effort has been allocated. From personal experience this is an endless process. However, this book is no exception to this rule. With feed-backs from future users of the book it is hoped to make the improvement changes needed that will be incorporated in future editions.

An improved model for the Earth's gravity field, TEG-1, has been determined using data sets from fourteen satellites, spanning the inclination ranges from 15°to 115°, and global surface gravity anomaly data. The satellite measurements include laser ranging data, doppler range-rate data, and satellite-to-ocean radar altimeter data measurements, which include the direct height measurement and the differenced measurements at ground track crossings (crossover measurements). Also determined was another gravity field model, TEG-1S, which included all the data sets in TEG-1 with the exception of direct altimeter data. The effort has included an intense scrutiny of the gravity field solution methodology. The estimated parameters included geopotential coefficients complete to degree and order 50 with selected higher order coefficients, ocean and solid Earth tide parameters, doppler tracking station coordinates and the quasi-stationary sea surface topography. Extensive error analysis and calibration of the formal covariance matrix indicate that the gravity field model is a significant improvement over previous models and can be used for general applications in geodesy.

American Journal of Geographical Research and Reviews, 2017

The main physical principle of gravity method application is the density difference between the various geological, environmental, archaeological, and other targets and host media. Gravity is one of the oldest geophysical methods, and it is widely applied for knowledge of subsurface and deep Earth's domains. The present review displays multiscale examples of gravity field examination, from very detailed (delineation of karst terranes and archaeological targets) to regional investigations (development of 3D physical-geological models and satellite data examination of giant regions). Geographically, the examined areas include the South Caucasus, Dead Sea, Eastern Mediterranean, and Arabian-African regions. Diverse methodologies of gravity data processing, qualitative and quantitative interpretation, and 3D gravity field modeling results are shown. It is demonstrated that integrating gravity field analysis with other geophysical methods (magnetic, paleomagnetic, thermal, seismic, etc.) significantly increases the accuracy and reliability of developed physical-geological models. Further ways of evaluation of gravity data analysis are considered.

Geodetic Sciences - Observations, Modeling and Applications, 2013

Geodesy and cartography, 2016

Site specific geoid model is prerequisite for accurate determination of orthometric heights. No geoid model has been developed so far for India or any of its part. So, development of a geoid model for India or its part is of utmost need to make use of GNSS data towards determination of orthometric heights. In this research work, an attempt has been made to develop geoid undulation models by gravimetric method using Molodensky’s concept. Component parameters in line with the Remove – Compute – Restore (RCR) technique have been used recursively. Models have been developed for two study areas: one of these lies in and around Dehradun (30° 19′ N, 75° 04′E) in Uttarakhand state, India in lower Himalayan region having highly undulating topography and the other near Hyderabad (17° 30′N, 78°30′E) in Telengana state of India having gentle topography. The model has been tested for 7 stations in the first study area and accuracy has been found to be 17.5 cm; whereas, for the second area accura...

2018

The Earth system generates different phenomena that are observable at the surface of the Earth such as mass deformations and displacements leading to plate tectonics, earthquakes, and volcanism. The dynamic processes associated with the interior, surface, and atmosphere of the Earth affect the three pillars of geodesy: shape of the Earth, its gravity field, and its rotation. Geodesy establishes a characteristic structure in order to define, monitor, and predict of the whole Earth system. The traditional and new instruments, observables, and techniques in geodesy are related to the gravity field. Therefore, the geodesy monitors the gravity field and its temporal variability in order to transform the geodetic observations made on the physical surface of the Earth into the geometrical surface in which positions are mathematically defined. In this paper, the main components of the gravity field modeling, (Free-air and Bouguer) gravity anomalies are calculated via recent global models (E...

The Gravity Model takes its name from Newton’s law of Universal Gravitation. According to Newton’s Law of Universal Gravitation, the force of gravitational attraction is directly dependent upon the masses of both objects and inversely proportional to the square of the distance between these objects. Similarly, according to the Gravity model in international trade, the trade volume between two countries are proportional to their GDP and inversely proportional to distance between them. The size and development level of the close-range economies has an important role on determining the economic progress of a country. While evaluating the enlargement capacity of trading volume and development processes of countries and regions, the distance to the other developed economies becomes an important factor. In this study, it is going to be examined that what the gravity model is, why it is so important, whether it is still valid or not, and how it is related with the international trade.