scholarly journals A Methodology for Filtering and Inversion of Gravity Data: An Example of Application to the Determination of the Moho Undulation in Morocco

Engineering ◽  
2010 ◽  
Vol 02 (03) ◽  
pp. 149-159 ◽  
Author(s):  
Victor Corchete ◽  
Mimoun Chourak ◽  
Driss Khattach
Keyword(s):  
Gravity Data ◽  
And Inversion

Evaluation of the latest GOCE GGMs in support of regional geoid modeling over Greece

2021 ◽  
Author(s):  
Georgios S. Vergos ◽  
Ilias N. Tziavos ◽  
Dimitrios A. Natsiopoulos ◽  
Elisavet G. Mamagiannou ◽  
Eleftherios A. Pitenis
Keyword(s):  
Maximum Degree ◽  
Gravity Data ◽  
Ground Truth ◽  
Satellite Gravity ◽  
Disturbing Potential ◽  
Geopotential Models ◽  
Potential Functionals ◽  
Geoid Computation ◽  
Goce Satellite

<p>In the frame of the GeoGravGOCE project, funded by the Hellenic Foundation for Research Innovation, GOCE Satellite Gravity Gradiometry (SGG) data are to be used for regional geoid and gravity field refinement as well as for potential determination in the frame of the International Height Reference Frame (IHRF). An inherent step in the geoid computation with either stochastic or spectral methods is the reduction of the related disturbing potential functionals within the well-known Remove-Compute-Restore (RCR) procedure. In this work we evaluate the latest, Release 6 (R6), satellite only and combined Global Geopotential Models (GGMs) which rely solely on GOCE and on land gravity data. The evaluation is performed over the established network of 1542 GPS/Levelling benchmarks over Greece mainland (BMs), which have been used in the past for the evaluation of GOCE GGMs. We employ the spectral enhancement approach, during which the GOCE-based GGMs are evaluated every one degree to the maximum degree of expansion coupled by EGM2008 and high-frequency RTM effects. This synthesis resolves wavelengths corresponding to maximum degree 216,000, hence the omission error is at the few mm-level. TIM-R6, DIR-R6, GOCO06s and XGM2019e are evaluated using EGM2008 residuals to the GPS/Levelling as the ground truth. From the results achieved, the optimal combination degree of a GOCE-only GGM augmented with EGM2008 is selected to be used in the sequel as reference field for the practical determination of the gravimetric geoid over Greece.</p>

scholarly journals Gravity reference at the Argentinean–German Geodetic Observatory (AGGO) by co-location of superconducting and absolute gravity measurements

2020 ◽  
Vol 94 (9) ◽  
Author(s):  
Ezequiel D. Antokoletz ◽  
Hartmut Wziontek ◽  
Claudia N. Tocho ◽  
Reinhard Falk
Keyword(s):  
Gravity Data ◽  
Total Error ◽  
International Comparisons ◽  
Superconducting Gravimeter ◽  
Calibration Factor ◽  
Absolute Gravity ◽  
Absolute Level ◽  
Gravity Measurements ◽  
Instrumental Drift

AbstractThe Argentinean–German Geodetic Observatory (AGGO) is a fundamental geodetic observatory located close to the city of La Plata, Argentina. Two high-precision gravity meters are installed at AGGO: the superconducting gravimeter SG038, which is in operation since December 2015, and the absolute gravimeter FG5-227, which has provided absolute gravity measurements since January 2018. By co-location of gravity observations from both meters between January 2018 and March 2019, calibration factor and instrumental drift of the SG038 were determined. The calibration factor of the SG038 was estimated by different strategies: from tidal models, dedicated absolute gravity measurements over several days and a joint approach (including the determination of the instrumental drift) using all available absolute gravity data. The final calibration factor differs from the determination at the previous station, the transportable integrated geodetic observatory, in Concepcion, Chile, by only 0.7‰, which does not imply a significant change. From the combined approach also the mean absolute level of the SG was determined, allowing to predict absolute gravity values from the SG at any time based on a repeatability of $$12\,\hbox {nm}/\hbox {s}^{2}$$ 12 nm / s 2 for the FG5-227 at AGGO. Such a continuous gravity reference function provides the basis for a comparison site for absolute gravimeters in the frame of the international gravity reference frame for South America and the Caribbean. However, it requires the assessment of the total error budget of the FG5-227, including the link to the international comparisons, which will be subject of future efforts.

Spectral analysis and inversion of experimental codas

Geophysics ◽  
1993 ◽  
Vol 58 (3) ◽  
pp. 408-418 ◽  
Author(s):  
L. R. Jannaud ◽  
P. M. Adler ◽  
C. G. Jacquin
Keyword(s):  
Spectral Analysis ◽  
Characteristic Length ◽  
Gaussian Model ◽  
Seismic Survey ◽  
Data Sets ◽  
Data Set ◽  
Anisotropic Elastic ◽  
And Inversion ◽  
Good Agreement

A method developed for the determination of the characteristic lengths of an heterogeneous medium from the spectral analysis of codas is based on an extension of Aki’s theory to anisotropic elastic media. An equivalent Gaussian model is obtained and seems to be in good agreement with the two experimental data sets that illustrate the method. The first set was obtained in a laboratory experiment with an isotropic marble sample. This sample is characterized by a submillimetric length scale that can be directly observed on a thin section. The spectral analysis of codas and their inversion yields an equivalent correlation length that is in good agreement with the observed one. The second data set is obtained in a crosshole experiment at the usual scale of a seismic survey. The codas are recorded, analysed, and inverted. The analysis yields a vertical characteristic length for the studied subsurface that compares well with the characteristic length measured by seismic and stratigraphic logs.

Reply by the author to G. D. Garland.

Geophysics ◽  
1982 ◽  
Vol 47 (10) ◽  
pp. 1460-1460
Author(s):  
B. A. Sissons
Keyword(s):  
Least Squares ◽  
Standard Error ◽  
Gravitational Constant ◽  
Gravity Data ◽  
Residual Distribution ◽  
Density Measurements ◽  
Least Squares Fit ◽  
Least Squares Adjustment ◽  
Sufficient Precision

Although the Tokaanu experiment does contradict the proposal that the gravitational constant G increases with scale, the result is not significant. The standard error in the least‐squares adjustment is at least 1 percent, which exceeds the predicted variation in G. The uncertainty in mean density is nearer 5 percent. Gravity data with sufficient precision to test for a scale effect in G are obtainable; the main problem appears to be the uncertainty in density determinations. Stacey et al (1981) made a least‐squares determination of G using gravity and density measurements from a mine. However, the pattern of residuals obtained indicated the presence of anomalous masses not adequately accounted for by their density averaging. The method I have used which models the spatial variation in density offers the possibility of obtaining a least‐squares fit for G with a satisfactory residual distribution. However, the problem of the effect on bulk density of joints and voids not sampled in hand specimens remains.

2D modeling and inversion of gravity data using density contrast varying with depth and source–basement geometry described by the Fourier series

Geophysics ◽  
2003 ◽  
Vol 68 (6) ◽  
pp. 1909-1916 ◽  
Author(s):  
Juan García‐Abdeslem
Keyword(s):  
Fourier Series ◽  
Gravity Data ◽  
Forward Modeling ◽  
Density Contrast ◽  
Nonlinear Inversion ◽  
Bouguer Gravity ◽  
Data Set ◽  
Cubic Polynomial ◽  
Broad Variety ◽  
And Inversion

A method is developed for 2D forward modeling and nonlinear inversion of gravity data. The forward modeling calculates the gravity anomaly caused by a 2D source body with an assumed depth‐dependent density contrast given by a cubic polynomial. The source body is bounded at depth by a smooth, curvilinear surface given by the Fourier series, which represents the basement. The weighted and damped discrete nonlinear inverse method presented here can invert gravity data to infer the geometry of the source body. The use of the Fourier series to define the basement geometry allows the interpreter to reconstruct a broad variety of geometries for the geologic structures using a small number of free parameters. Both modeling and inversion methods are illustrated with examples using field gravity data across the San Jacinto graben in southern California and across the Sayula basin in Jalisco, Mexico. The inversion of the San Jacinto graben residual Bouguer gravity data yields results compatible with those from previous interpretations of the same data set, suggesting that this geologic structure accommodates about 2.5 km of sediments. The inversion of the residual Bouguer gravity data across the Sayula basin suggests a maximum of 1‐km‐thick sedimentary infill.

Design and synthesis of near-infrared absorbing pigments. II. Structure determination of aceanthrene green and derivatives

1995 ◽  
Vol 73 (3) ◽  
pp. 325-335 ◽  
Author(s):  
Denis Désilets ◽  
Peter M. Kazmaier ◽  
Richard A. Burt ◽  
Gordon K. Hamer
Keyword(s):  
Potassium Hydroxide ◽  
Near Infrared ◽  
Benzimidazole Derivative ◽  
Frontier Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Design And Synthesis ◽  
H Nmr ◽  
Polycyclic Aromatic ◽  
And Inversion

The reported structure of aceanthrene green, a pigment prepared by potassium hydroxide fusion of 1,9-anthracenedicarboxylic imide, was found to be incorrect. The structure of the pigment is reassigned to 7,8,15,16-dibenzo[a,j]perylenetetracarboxylic diimide on the basis of COSY, NOESY, and inversion–recovery 1H NMR experiments. N-Alkyl- or N-phenyl-1,9-anthracenedicarboxylic imides, aceanthryleno[1,2-b]quinoxaline, and a benzimidazole derivative of 1,9-anthracenedicarboxylic anhydride were found to give the same dibenzo[a,j]perylene structure when reacted in potassium hydroxide. The electronic spectra of these derivatives is reported and it is shown that, as predicted by Pariser–Parr–Pople calculations, they absorb in the near-infrared. Finally, a mechanistic outline for the fusion is proposed on the basis of AM1 and frontier molecular orbital calculations. Keywords: photoconductor, near-infrared, aceanthrene green, alkalifusion, polycyclic aromatic hydrocarbon.

An analytic method for the determination of distant terrain corrections

Geophysics ◽  
1982 ◽  
Vol 47 (10) ◽  
pp. 1453-1455 ◽  
Author(s):  
Z. F. Danés
Keyword(s):  
Gravity Field ◽  
Analytical Methods ◽  
Gravity Data ◽  
Analytic Method ◽  
Topographic Map ◽  
Terrain Corrections

Terrain corrections of gravity data are by far the most awkward and time‐consuming reductions needed in exploration geophysics. The terrain must be subdivided into small prisms; the average elevation of each prism must be found on a topographic map; the gravity field of each prism must be determined by analytical methods; and the contributions of all the prisms must be added up.

On: “Determination of crustal interface topography from potential fields” by M. Pilkington and D. J. Crossley (GEOPHYSICS, 51, 1277–1284, June 1986) and “Inversion of aeromagnetic data for multilayered models” by M. Pilkington and D. J. Crossley (GEOPHYSICS, 51, 2250–2254, December 1986).

Geophysics ◽  
1987 ◽  
Vol 52 (10) ◽  
pp. 1436-1437
Author(s):  
Nelson C. Steenland
Keyword(s):  
Magnetic Field ◽  
New Mexico ◽  
Oil And Gas ◽  
Potential Fields ◽  
Main Magnetic Field ◽  
Aeromagnetic Data ◽  
Oil And Gas Exploration ◽  
And Inversion

The introduction of the airborne magnetometer in the 1940s led to the largest flow of data in geophysical history. Vacquier (1951) recognized the need for a concomitant system of interpretation of these data and pioneered the utilization of a rejected category of anomalies, the intrabasement contrasts in magnetization, for the basis of the desired system. These anomalies had great acclaim in oil and gas exploration in the late 1920s, but they led to the total disrepute of magnetics when facsimiles to the coincidence of production and intrabasement magnetization at Hobbs, New Mexico, discovered in 1928, did not achieve the same relationship. But Vacquier recognized the omnipresence of these anomalies, the singularity of individual anomalies, and their source in thick bodies of relatively steep sides and induced magnetizations. These simple but powerful deductions were reached pragmatically. To repeat, anomalies were singular because they were quite separate from one another. Therefore, the sides of their causative bodies had to be quite steep. An anomaly must be attributed to one magnetization contrast because it was one anomaly, and that magnetization was induced because the ratios of their positive and negative components correlated with the inclination of the Earth’s main magnetic field. (All of this may be found in GSA Memoir 47, 1951.)

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