Complete spherical Bouguer gravity anomalies over Australia

Kühn, Michael; Featherstone, Will; Kirby, Jonathan

doi:10.1080/08120090802547041

Cited by 41 publications

(46 citation statements)

References 38 publications

(45 reference statements)

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“…The present study was triggered by the goal of computing a global Bouguer map, and by the work of Kuhn et al (2009), who define and compute what they call complete spherical Bouguer gravity anomalies (Δg CSB ) using spherical terrain corrections over the whole Earth with respect to a local but full spherical Bouguer shell. Such an anomaly, at any gravity observation point P of altitude H , involves: (i) the gravitational effect of the Bouguer shell of constant thickness H and density ρ, that is 4πGρ H (twice the value of the usual plateau term-G being the gravitational constant); and (ii) the spherical terrain correction with respect to the shell, computed over the whole planet by numerical integration over spherical volume elements having a size which increases with the distance to point P. Then the free air correction, atmospheric correction and normal gravity (at the reference ellipsoid surface) are used to achieve the computation of Δg CSB .…”

Section: Introductionmentioning

confidence: 99%

Spherical harmonic modelling to ultra-high degree of Bouguer and isostatic anomalies

Balmino

Valès

Bonvalot

et al. 2011

J Geod

301

221

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The availability of high-resolution global digital elevation data sets has raised a growing interest in the feasibility of obtaining their spherical harmonic representation at matching resolution, and from there in the modelling of induced gravity perturbations. We have therefore estimated spherical Bouguer and Airy isostatic anomalies whose spherical harmonic models are derived from the Earth's topography harmonic expansion. These spherical anomalies differ from the classical planar ones and may be used in the context of new applications. We succeeded in meeting a number of challenges to build spherical harmonic models with no theoretical limitation on the resolution. A specific algorithm was developed to enable the computation of associated Legendre functions to any degree and order. It was successfully tested up to degree 32,400. All analyses and syntheses were performed, in 64 bits arithmetic and with semi-empirical control of the significant terms to prevent from calculus underflows and overflows, according to IEEE limitations, also in preserving the speed of a specific regular grid processing scheme. Finally, the continuation from the reference ellipsoid's surface to the Earth's surface was performed by high-order Taylor expansion with all grids of required partial derivatives being computed in parallel. The main application was the production of a 1 × 1 equiangular global Bouguer anomaly grid which was computed by spherical harmonic analysis of the Earth's topographybathymetry ETOPO1 data set up to degree and order 10,800, taking into account the precise boundaries and densities of major lakes and inner seas, with their own altitude, polar caps with bedrock information, and land areas below sea level. The harmonic coefficients for each entity were derived by analyzing the corresponding ETOPO1 part, and free surface data when required, at one arc minute resolution. The following approximations were made: the land, ocean and ice cap gravity spherical harmonic coefficients were computed up to the third degree of the altitude, and the harmonics of the other, smaller parts up to the second degree. Their sum constitutes what we call ETOPG1, the Earth's TOPography derived Gravity model at 1 resolution (half-wavelength). The EGM2008 gravity field model and ETOPG1 were then used to rigorously compute 1 × 1 point values of surface gravity anomalies and disturbances, respectively, worldwide, at the real Earth's surface, i.e. at the lower limit of the atmosphere. The disturbance grid is the most interesting product of this study and can be used in various contexts. The surface gravity anomaly grid is an accurate product associated with EGM2008 and ETOPO1, but its gravity information contents are those of EGM2008. Our method was validated by comparison with a direct numerical integration approach applied to a test area in Morocco-South of Spain (Kuhn, private communication 2011) and the agreement was satisfactory. Finally isostatic corrections according to the Airy model, but in spherical geometry, with harmonic coeffi...

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Section: Introductionmentioning

confidence: 99%

Spherical harmonic modelling to ultra-high degree of Bouguer and isostatic anomalies

Balmino

Valès

Bonvalot

et al. 2011

J Geod

301

221

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“…Recently, new formulations have been proposed to compute gravity anomalies based on both a realistic Earth model and rigorous geodetic definitions. More details on these modern views of anomaly computation can be found in Featherstone and Dentith (1997), Li and Götze (2001), Hackney and Featherstone (2003), Hinze et al (2005), NGA (2008) and Kuhn et al (2009). esr.ccsenet.org Earth Science Research Vol.…”

Section: Methodsmentioning

confidence: 99%

Geometrical Characterisation of the Mamfe Basin, Cameroon, from the Earth, Gravitational Model (EGM 2008)

Lordon¹,

Yossa²,

Agyingi³

et al. 2018

ESR

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Gravimetric studies using the ETOPO1-corrected high resolution satellite-based EGM2008 gravity data was used to define the surface extent, depth to basement and shape of the Mamfe basin. The Bouguer anomaly map was produced in Surfer 11.0. The Fast Fourier Transformed data was analyzed by spectral analysis to remove the effect of the regional bodies in the study area. The residual anomaly map obtained was compared with the known geology of the study area, and this showed that the gravity highs correspond to the metamorphic and igneous rocks while the gravity lows match with Cretaceous sediments. Three profiles were drawn on the residual anomaly map along which 2D models of the Mamfe basin were drawn. The modeling was completed in Grav2dc v2.06 software which uses the Talwini's algorithm and the resulting models gave the depth to basement and the shape of the basement along the profiles. After processing and interpretation, it was deduced that the Mamfe basin has an average length and width of 77.6 km and 29.2 km respectively, an average depth to basement of 5 km and an overall U-shape basement. These dimensions (especially the depth) theoretically create the depth and temperature conditions for petroleum generation.

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“…Previously the terrain correction has been calculated for the entirety of Australia (Kuhn et al 2009). However, this previous work used a 9 second DEM, which is equivalent to approximately 250 metre resolution.…”

Section: Introduction and Methodsmentioning

confidence: 99%