scholarly journals Application of BEMD in Extraction of Regional and Local Gravity Anomalies Reflecting Geological Structures Associated with Mineral Resources

2018 ◽  
Author(s):  
Yongqing Chen ◽  
Binbin Zhao ◽  
Jingnning Huang ◽  
Lina Zhang
Keyword(s):  
Mineral Resources ◽  
Gravity Anomalies ◽  
Geological Structures ◽  
Local Gravity

Robust inversion analysis of local gravity anomalies caused by geological dislocation model of faults

1998 ◽  
Vol 11 (1) ◽  
pp. 103-113 ◽  
Author(s):  
Jian-Liang Huang ◽  
Chong-Yang Shen ◽  
Hui Li
Keyword(s):  
Gravity Anomalies ◽  
Dislocation Model ◽  
Local Gravity ◽  
Inversion Analysis

BOUGUER GRAVITY CORRECTIONS USING A VARIABLE DENSITY

Geophysics ◽  
1962 ◽  
Vol 27 (5) ◽  
pp. 616-626 ◽  
Author(s):  
F. S. Grant ◽  
A. F. Elsaharty
Keyword(s):  
Least Squares ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Variable Density ◽  
Bouguer Gravity ◽  
Method Of Least Squares ◽  
Surface Conditions ◽  
Worked Example ◽  
Local Gravity

The principle of density profiling as a means of determining Bouguer densities is studied with a view to extending it to include all of the data in a survey. It is regarded as an endeavor to minimize the correlation between local gravity anomalies and topography, and as such it can be handled mathematically by the method of least squares. In the general case this leads to a variable Bouguer density which can be mapped and contoured. In a worked example, the correspondence between this function and the known geology appears to be good, and indicates that Bouguer density variations due to changing surface conditions can be used routinely in the reduction of gravity data.

A least‐squares minimization approach to invert gravity data

Geophysics ◽  
1991 ◽  
Vol 56 (1) ◽  
pp. 115-118 ◽  
Author(s):  
E. M. Abdelrahman ◽  
A. I. Bayoumi ◽  
H. M. El‐Araby
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Gravity Data ◽  
Spline Approximation ◽  
Gravity Anomalies ◽  
Approximation Techniques ◽  
Local Gravity ◽  
Fourier Transform Methods ◽  
Minimization Approach ◽  
Least Squares Minimization

The interpretation of gravity data often involves initial steps to eliminate or attenuate unwanted field components in order to isolate the desired anomaly (e.g., residual‐regional separations). These initial filtering operations include, for example, the radial weights methods (Griffin, 1949; Elkins, 1951; Abdelrahman et al., 1990), the fast Fourier transform methods (Bhattacharyya, 1965; Clarke, 1969; Meskó, 1969, 1984, Botezatu, 1970), the rational approximation techniques (Agarwal and Lal, 1971) and recursion filters (Bhattacharyya, 1976), and the bicubic spline approximation techniques (Bhattacharyya, 1969; Inoue, 1986). The derived local gravity anomalies are then geologically interpreted to derive depth estimates, often without properly accounting for the uncertainties introduced by the filtering process. When filters are applied to observed data, the filters often cause serious distortions in the shape of the gravity anomalies (Hammer, 1977). Thus the filtered gravity anomalies generally yield unreliable geologic interpretations (Rao and Radhakrishnamurthy, 1965; Hammer, 1977; Abdelrahman et al., 1985, 1989.

GRATICULE SPACING VERSUS DEPTH DISCRIMINATION IN GRAVITY INTERPRETATION

Geophysics ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 60-65 ◽  
Author(s):  
Sigmund Hammer
Keyword(s):  
Gravity Anomalies ◽  
Second Derivative ◽  
Practical Procedure ◽  
Depth Discrimination ◽  
Local Gravity ◽  
Gravity Interpretation ◽  
Local Anomalies ◽  
Residual Maps

Very serious distortions in both magnitude and extension of local gravity anomalies result from the still widely used 9-point “residual” and 17-point “second derivative” graticules. Although these types of residual maps are very useful for recognizing and pinpointing the existence of interesting local anomalies, the distorted results cannot be used to derive geologic interpretations of significant reliability. A practical procedure based on changes in anomaly magnitudes from two (or more) different grid spacings, effectively overcomes shortcomings of previous interpretation methods.

scholarly journals MANAGING GEOLOGICAL PROFILES IN DATABASES FOR 3D VISUALISATION

2016 ◽  
Vol XLII-2/W2 ◽  
pp. 115-121
Author(s):  
A. Jarna ◽  
B. O. Grøtan ◽  
I. H. C. Henderson ◽  
S. Iversen ◽  
E. Khloussy ◽  
...  
Keyword(s):  
3D Model ◽  
Three Dimensional ◽  
Mineral Resources ◽  
Marine Geology ◽  
Geological Data ◽  
Geological Structures ◽  
Use Of Data ◽  
Rock Structure ◽  
Surficial Deposits ◽  
The Web

Geology and all geological structures are three-dimensional in space. GIS and databases are common tools used by geologists to interpret and communicate geological data. The NGU (Geological Survey of Norway) is the national institution for the study of bedrock, mineral resources, surficial deposits and groundwater and marine geology. 3D geology is usually described by geological profiles, or vertical sections through a map, where you can look at the rock structure below the surface. The goal is to gradually expand the usability of existing and new geological profiles to make them more available in the retail applications as well as build easier entry and registration of profiles. The project target is to develop the methodology for acquisition of data, modification and use of data and its further presentation on the web by creating a user-interface directly linked to NGU’s webpage. This will allow users to visualise profiles in a 3D model.

scholarly journals Modelling Local Gravity Anomalies from Processed Observed Gravity Measurements for Geodetic Applications

2019 ◽  
pp. 144-162
Author(s):  
Eteje S. O. ◽  
Oduyebo O. F. ◽  
Oluyori P. D.
Keyword(s):  
Applied Sciences ◽  
Gravity Anomalies ◽  
Absolute Gravity ◽  
Bouguer Gravity ◽  
Benin City ◽  
Bouguer Gravity Anomalies ◽  
Free Air ◽  
Local Gravity ◽  
Gravity Measurements ◽  
Mean Square Errors

As the application of gravity data in applied sciences such as geodesy, geodynamics, astronomy, physics and geophysics for earth shape determination, geoid model determination, computation of terrestrial mass displacement, orbit computation of natural and artificial celestial bodies, realization of force standards and derived quantities and density distribution in the different layers in the upper crust and having considered the cost of direct gravity survey, the study presents modelling local gravity anomalies from processed observed gravity measurements for geodetic application in Benin City. A total of 22 points were used. The points were respectively observed with CHC900 dual frequency GNSS receivers and SCINTREX CG-5 Autograv to obtain their coordinates and absolute gravity values. The theoretical gravity values of the points were computed on the Clarke 1880 ellipsoid to obtain their local gravity anomalies. The free air and the Bouguer corrections were applied to the computed gravity anomalies to obtain the free air and the Bouguer gravity anomalies of the points. Least squares adjustment technique was applied to obtain the model variables coefficient/parameters, as well as to fit the fifth-degree polynomial interpolation surface to the computed free air and the Bouguer gravity anomalies. Kriging method was applied using Surfer 12 software to plot the computed and the models' free air and Bouguer gravity anomalies. Microsoft Excel programs were developed for the application of the models in the study area. The Root Mean Square Errors (RMSEs) and the standard errors of the two models were computed to obtain the dependability, as well as reliability of the models. It is recommended that whenever either free air or Bouguer gravity anomalies of points within Benin City are to be obtained for application in applied sciences, the determined models should be applied.

scholarly journals Evaluating Accuracy of HY-2A/GM-Derived Gravity Data With the Gravity-Geologic Method to Predict Bathymetry

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhijie Wei ◽  
Jinyun Guo ◽  
Chengcheng Zhu ◽  
Jiajia Yuan ◽  
Xiaotao Chang ◽  
...  
Keyword(s):  
Gravity Data ◽  
Bottom Topography ◽  
Gravity Anomalies ◽  
Processing Method ◽  
Ocean Bottom ◽  
Least Squares Collocation ◽  
Geological Structures ◽  
Data Processing Method ◽  
First Time ◽  
Assessment Result

For the first time, HY-2A/GM-derived gravity anomalies determined with the least-squares collocation method and ship-borne bathymetry released from the National Centers for Environmental Information (NCEI) are used to predict bathymetry with the gravity-geologic method (GGM) over three test areas located in the South China Sea (105–122°E, 2–26°N). The iterative method is used to determine density contrasts (1.4, 1.5, and 1.6 g/cm3) between seawater and ocean bottom topography, improving the accuracy of GGM bathymetry. The results show that GGM bathymetry is the closest to ship-borne bathymetry at check points, followed by SRTM15+V2.0 model and GEBCO 2020 model. It is found that in a certain range, the relative accuracy of GGM bathymetry tends to improve with the increase of depth. Different geological structures affect the accuracy of GGM bathymetry. In addition, the influences of gravity anomalies and data processing method on GGM bathymetry are analyzed. Our assessment result suggests that GGM can be widely applied to bathymetry prediction and that HY-2A/GM-derived gravity data are feasible with good results in calculating ocean depth.

QUANTITATIVE ANALYSIS OF THE RELATIONSHIP BETWEEN THE SIZE AND LOCATION OF OIL AND GAS FIELDS WITH GRAVITATIONAL ANOMALIES OF THE FERGANA DEPRESSION

2020 ◽  
Vol 2020 (3) ◽  
pp. 95-112
Author(s):  
R Umurzakov ◽  
◽  
S Rabbimkulov
Keyword(s):  
Oil And Gas ◽  
Gravity Anomalies ◽  
Geological Structure ◽  
Gas Content ◽  
Effective Volume ◽  
Oil And Gas Fields ◽  
Local Gravity ◽  
Gas Fields ◽  
The Impact ◽  
Gravitational Anomalies

Based on the analysis of published materials, it is noted that the degree of connection between the indicators of the anomalies of the gravitational field and oil and gas content remains unclear. The aim of the research was to study the nature of the dependence and assess the degree of connection between the size and location of oil and gas fields with gravitational anomalies using the example of the Fergana oil and gas region. To solve this problem, the published material on the geological structure and data on the sizes (effective volume) of deposits, as well as data on deep anomalies of the gravity field in the Fai reduction, were used. The study involved about 70 deposits. Analysis of variance showed that the “influence” of the deep anomaly factor on the effective volume of the fields in the Fergana depression is significant and reliable with a probability of 0.99. At the same time, the share of the influence of this factor on the effective volume of oil deposits in relation to the total impact of all factors is 42%, and for oil and gas - 62%. This testifies to the significant influence of deep subcrustal processes that create corresponding gravitational effects on the formation of the size and location of oil and gas fields in the Fergana depression. According to local gravity anomalies, the impact on the location and effective volumes of deposits is significant, but the reliability is low. The degree of influence on them remains unclear. The results obtained can be used to develop methods for forecasting promising areas for performing high-priority geological exploration works.

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