Gravity interpretation using correlation factors between successive least‐squares residual anomalies

Abdelrahman, E. M.; Bayoumi, A. I.; Abdelhady, Y. E.; Gobashy, Mohamed; El-Araby, Hesham M.

doi:10.1190/1.1442629

Cited by 75 publications

(40 citation statements)

References 21 publications

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“…Singular values and their variabilities in percentage of the sensitivity matrix, which was calculated from the initial guess shown at the top panel of Fig. 15 regular body. Nevertheless, these regular models often yield a first approximation solution, which is sometimes quite adequate (e.g., Abdelrahman et al 1989;Mehanee 2014a).…”

Section: Discussionmentioning

confidence: 99%

“…Gravity and magnetic methods have many successful applications in mineral prospecting, environmental applications, and crustal imaging (e.g., Abdelrahman et al 1989;Ateya and Takemoto 2002;Batista-Rodríguez et al 2013;Beiki and Pedersen 2011;Fedi 2007;Hinze 1990;Hinze et al 2013;LaFehr and Nabighian 2012;Long and Kaufmann 2013;Mehanee 2014a;Nettleton 1976;Okubo et al 2013;Paoletti et al 2013;Pei et al 2014).…”

Section: Introductionmentioning

confidence: 99%

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2.5D regularized inversion for the interpretation of residual gravity data by a dipping thin sheet: numerical examples and case studies with an insight on sensitivity and non-uniqueness

Mehanee

Essa

2015

Earth Planet Sp

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A new two-and-a-half dimensional (2.5D) regularized inversion scheme has been developed for the interpretation of residual gravity data by a dipping thin-sheet model. This scheme solves for the characteristic inverse parameters (depth to top z, dip angle θ , extension in depth L, strike length 2 Y, and amplitude coefficient A) of a model in the space of logarithms of these parameters (log(z), log(θ ), log(L), log(Y), and log(|A|)). The developed method has been successfully verified on synthetic examples without noise. The method is found stable and can estimate the inverse parameters of the buried target with acceptable accuracy when applied to data contaminated with various noise levels. However, some of the inverse parameters encountered some inaccuracy when the method was applied to synthetic data distorted by significant neighboring gravity effects/interferences. The validity of this method for practical applications has been successfully illustrated on two field examples with diverse geologic settings from mineral exploration. The estimated inverse parameters of the real data investigated are found to generally conform well with those yielded from drilling. The method is shown to be highly applicable for mineral prospecting and reconnaissance studies. It is capable of extracting the various characteristic inverse parameters that are of geologic and economic significance, and is of particular value in cases where the residual gravity data set is due to an isolated thinsheet type buried target. The sensitivity analysis carried out on the Jacobian matrices of the field examples investigated here has shown that the parameter that can be determined with the superior accuracy is θ (as confirmed from drilling information). The parameters z, L, Y, and A can be estimated with acceptable accuracy, especially the parameters z and A. This inverse problem is non-unique. The non-uniqueness analysis and the tabulated inverse results presented here have shown that the parameters most affected by the non-uniqueness are L and Y. It has also been shown that the new scheme developed here is advantageous in terms of computational efficiency, stability and convergence than the existing gravity data inversion schemes that solve for the characteristic inverse parameters of a sheet/dike.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

2.5D regularized inversion for the interpretation of residual gravity data by a dipping thin sheet: numerical examples and case studies with an insight on sensitivity and non-uniqueness

Mehanee

Essa

2015

Earth Planet Sp

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“…It consists of determining the altitude of the upward continuation of the Bouguer where the curve of correlation between the extended fields of the successive altitudes shows a maximum deflection. The process of data treatment in order to determine this altitude in our study area consists of: Carrying out several upward extensions to altitudes ranging from 5 to 125 km of the Bouguer anomaly map in 5 km intervals, then, using the relation (1) proposed by [24], calculate the correlation factors between the extended fields at two successive altitudes (g1 and g2). …”

Section: Methodsmentioning

confidence: 99%

“…It is worthwhile to note that [21,22,24] successfully used this method in their respective study areas.…”

Section: Methodsmentioning

confidence: 99%

Geophysical Signature Location in the South-West of Chad: Structural Implications

Benoit¹,

Nouayou²,

Victor³

et al. 2017

J Geol Geophys

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IntroductionChad corresponds to the mobile zone formed during the PanAfrican orogenesis that occurred at Proterozoic between 830 and 665Ma [1]. This mobile zone is bounded to the south by the Congo Craton, to the West by the West African Craton and to the NorthEast by the metacraton of the Sahara. It appears that the whole of the Precambrian formations were marked by a strong imprint during the Pan-African events.These Precambrian formations identified in Chad are distributed between the Tibesti massifs in the north, Ouaddaï in the east, Yadé (Mbaibokoum) in the south and the Mayo-kebbi in the South-west. They cover 15 to 20% of the surface of the national territory [2].The secondary formations appear in the Erdis basin (Cretaceous Nubian sandstone) and the Mayo-Kebbi (Lower Cretaceous and Middle Cretaceous) basin. They also constitute the filling of several pits in Southern Chad (Lake Chad, Bousso, Doba, Salamat). They are sandstones of the intercalary continental and those of the Cretaceous with lagoon and marine features. The Pala-Lame basin located in Mayo-Kebbi, in the Southwest of Chad near the border with Cameroon, is part of the Yadé massif, a large outcrop of the Precambrian basement which extends to Cameroon, the Republic of Central Africa, Congo and Gabon, and includes the Congo Craton [3].The region consists essentially of a large granite batholith (MayoKebbi batholith), containing septa of metamorphites and two strips of volcano-sedimentary metamorphic epikeal formations similar to the greenstone belts [3,4]. The whole is intersected by a series of intrusive and vein rocks, ranging from alkaline granite to ultrabasic rocks.Although the results of the various works cited above provided useful information over the study area, none of them proposed the cartography of the lineaments therein in a precise way. The latter is the objective of the present study. The Bouguer anomaly map of the study area has strong contrasts (gradients) that indicate discontinuities such as faults and flexures. In order to study these discontinuities, we conducted an analysis based on the horizontal gradient of the vertical derivative coupled with upward continuation and Euler's deconvolution. These approaches that have been successfully used in AbstractA Study is conducted in South-West of Chad with the goal of underlining the different lineaments of the region, which are entirely or partially hidden by the sedimentary cover. Different gravity data processing techniques including horizontal gradient of vertical derivative coupled with upward continuation and Euler's de-convolution are used. These methods revealed a number of lineaments describing gravity density discontinuities whose directions are N-S, NE-SW, ENE-WSW, and WNW-ESE at NNW-SSE. However, the predominant direction for major lineaments is WNW-ESE. The major lineaments associated to the faults are: F1, F2, F3, F6, F7, F8, F9, F10, F14, F21, F22, F23, F24 and F28. Euler's solutions indicate depths up to 9.2 km for the anomaly sources. Such lineaments are very usefu...

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“…Initially tuned PSO is demonstrated on synthetic data created by Eq. (1) in the text (Abdelrahman et al, 1989) and details about synthetic data were given in Sect. 4.1.…”

Section: Data Availabilitymentioning

confidence: 99%

Inversion of residual gravity anomalies using tuned PSO

Roshan

Singh

2017

Geosci. Instrum. Method. Data Syst.

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Abstract. Many kinds of particle swarm optimization (PSO) techniques are now available and various efforts have been made to solve linear and non-linear problems as well as onedimensional and multi-dimensional problems of geophysical data. Particle swarm optimization is a metaheuristic optimization method that requires intelligent guesswork and a suitable selection of controlling parameters (i.e. inertia weight and acceleration coefficient) for better convergence at global minima. The proposed technique, tuned PSO, is an improved technique of PSO, in which efforts have been made to choose the controlling parameters, and these parameters have been selected after analysing the responses of various possible exercises using synthetic gravity anomalies over various geological sources. The applicability and efficacy of the proposed method is tested and validated using synthetic gravity anomalies over various source geometries. Finally, tuned PSO is applied over field residual gravity anomalies of two different geological terrains to find the model parameters, namely amplitude coefficient factor (A), shape factor (q) and depth (z). The analysed results have been compared with published results obtained by different methods that show a significantly excellent agreement with real model parameters. The results also show that the proposed approach is not only superior to the other methods but also that the strategy has enhanced the exploration capability of the proposed method. Thus tuned PSO is an efficient and more robust technique to achieve an optimal solution with minimal error.

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Gravity interpretation using correlation factors between successive least‐squares residual anomalies

Cited by 75 publications

References 21 publications

2.5D regularized inversion for the interpretation of residual gravity data by a dipping thin sheet: numerical examples and case studies with an insight on sensitivity and non-uniqueness

2.5D regularized inversion for the interpretation of residual gravity data by a dipping thin sheet: numerical examples and case studies with an insight on sensitivity and non-uniqueness

Geophysical Signature Location in the South-West of Chad: Structural Implications

Inversion of residual gravity anomalies using tuned PSO

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