Normalized Full Gradient Methods Of Gravity Anomalies And Its Application

Gravitation is a historied, classical important branch of earth science. Gravitation concerns the gravity changes with time and space and the law of the changes.It is a basic and applied basic science that can be used in geodetic survey,internal constitution study,geodynamics,resource prospecting,engineering construction,disaster preparedness,etc.The densityvariation between object of study(mineral resource or geologic structure)and country rock is the precondition of gravitational prospecting.The gravity anomaly that caused only by density uneven mineral or geologic structure can get by rejecting the irrelevant factors in observeddata,further explaintion of the anomaly can make us more approaching to prospecting mine.To achieve the prospecting aim,theoretical study,principle of measurement,technique of measurement,develop better instrument,both are important contents of graviation.Establishing of geologic models of internal structure ,solid mineral resources,existing form of oil-gas are the foundation of important components of gravitation that include using gravity anomaly to study internal structure,solid mineral resources,existing form of oil-gas,stability of major works,and then the study of the forward and invert problem of different geologic models, integratedinterpretation and joint inversion between geologic data and geophysics data,now are the main trend of gravitation study.Meanwhile,development of new method and new technic that can improve the resolution of gravitational prospecting is the urgent task.The normalized full gradient(NFG) methods is first raised by the former soviet union in order to find oil resource directly.The NFG methods fit the gravity data in fourier series,and then the charcater of analytic functions that un-analytic in its field source can make us do downward-continuation to determine the space positions of the field source.To determine the horizontal projection position of the geologic body without prior constraint conditions is the NFG's advantage,further to know the depth of the body need a exact harmonic number.By use NFG we can determine the space position and space division of geologic body or geologicstructure,this is especially fit for quick gravitational prospecting to find prospective mine or oil-gas resources in unexplored areas.In the paper we first introduced the computational procedure of NFG,and then do theoretical calculation based on several geologic models.Results show that the NFG can well distinguish difference geologic models in a handy way.In the final we put the NFG into practical gravitational prospecting in a metal mineral area and get a satisfactory result.