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 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.

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.

Probing the Earth’s gravity field by means of satellite-to-satellite tracking

1977 ◽  
Vol 284 (1326) ◽  
pp. 475-483 ◽  
Keyword(s):  
Gravity Field ◽  
Signal To Noise Ratio ◽  
Gravity Anomalies ◽  
Small Variation ◽  
Satellite Tracking ◽  
Practical Advantage ◽  
Earth’S Gravity Field ◽  
Ground Station ◽  
Local Gravity ◽  
Range Rate

The idea of tracking one spacecraft from another grew out of some tracking studies performed early in the Apollo programme (1962-3). The main practical advantage of such a technique is that ( a ) contact time with a low orbiting spacecraft can be increased considerably (approximately 50 min v . 5 min for a single ground station); ( b ) the number of ground stations can be reduced; ( c ) the dependency on stations on foreign soil can almost be eliminated; and ( d ) detailed studies of spacecraft motions due to small variations in the Earth’s gravity field (anomalies) may be detectable. This paper describes specifically two satellite-to-satellite tracking (s. s. t.) tests, namely ( a ) the ATS-6/Geos-3 and ( b ) the ATS-6/Apollo-Soyuz experiment and some of the results obtained. The main purpose of these two experiments was first to track via ATS-6 the Geos-3 as well as the Apollo-Soyuz and to use these tracking data to determine ( a ) both orbits, that is, ATS-6, Geos-3 and/or the Apollo-Soyuz orbits at the same time; ( b ) each of these orbits alone, and ( c ) test the ATS-6/Geos-3 and /or Apollo-Soyuz s. s. t. link to study local gravity anomalies; and, second, to test communications, command and data transmission from the ground via ATS-6 to these spacecraft and back again to the ground (Rosman, N. G.). Most of the interesting data obtained to date originate from the Apollo-Soyuz geodynamics experiment. Thus, it will be discussed in some detail. Gravity anomalies of say 3-5 mGal (3-5 × 10 -5 m s -2 ) or larger having wavelength of 500-1000 km on the Earth’s surface are important for studies of the upper layers of the earth. Such anomalies were actually ‘seen’ for the first time from space as signatures in the form of very small variation (order of ~ 1 to 2 cm/s) in the range rate between ATS-6, Geos-3 and Apollo-Soyuz. Since the measured range noise turned out to be only 0.03- 0.05 cm/s on the average, these signatures were detected with an excellent signal-to-noise ratio. Orbit determination examples using s. s. t. data from ATS-6 and Geos-3 are also discussed in detail together with errors associated with the orbits of Geos-3. Further, signature studies and gravity anomaly detections with s. s. t. data will be shown and discussed in detail.

scholarly journals Application of Radial Basis Functions for Height Datum Unification

Geosciences ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 369 ◽  
Author(s):  
Ismael Foroughi ◽  
Abdolreza Safari ◽  
Pavel Novák ◽  
Marcelo Santos
Keyword(s):  
Gravity Field ◽  
Satellite Altimetry ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Basis Functions ◽  
Gravity Potential ◽  
Field Modelling ◽  
Marine Gravity ◽  
Local Gravity ◽  
Local Gravity Field Modelling

Local gravity field modelling demands high-quality gravity data as well as an appropriate mathematical model. Particularly in coastal areas, there may be different types of gravity observations available, for instance, terrestrial, aerial, marine gravity, and satellite altimetry data. Thus, it is important to develop a proper tool to merge the different data types for local gravity field modelling and determination of the geoid. In this study, radial basis functions, as a commonly useful tool for gravity data integration, are employed to model the gravity potential field of the southern part of Iran using terrestrial gravity anomalies, gravity anomalies derived from re-tracked satellite altimetry, marine gravity anomalies, and gravity anomalies synthesized from an Earth gravity model. Reference GNSS/levelling (geometric) geoidal heights are used to evaluate the accuracy of the estimated local gravity field model. The gravimetric geoidal heights are in acceptable agreement with the geometric ones in terms of the standard deviation and the mean value which are 4.1 and 12 cm, respectively. Besides, the reference benchmark of the national first-order levelling network of Iran is located in the study area. The derived gravity model was used to compute the gravity potential difference at this point and then transformed into a height difference which results in the value of the shift of this benchmark with respect to the geoid. The estimated shift shows a good agreement with previously published studies.

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