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Showing 1 to 20 of 39 for “"Geoid"”.
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Towards a geoid consistent vertical datum in South Africa
… a few. Therefore there is a need to establish a geoid-based vertical datum to mitigate the limitations of mean sea level based vertical datum and to open further frontiers in geodesy, geophysics and geodynamics research, and related applications. Establishment of a national geoid-based vertical …
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The use of spectral methods in Quasi-geoid modelling
Bibliography: leaves 105-111.
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The effect of a low density residuum on geoid anomalies and topography
… surface topography, seismic wave speed, and the geoid (gravitational potential). High seismic wave speed indicates cold material sinking, which pulls the surface downward. Thus, topographic lows are expected to correlate with seismic wave speed highs, contrary to the new seismic measurements. We …
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A comparison of the least squares collocation and the fast Fourier transform methods for gravimetric geoid determination
… transform (FFT) techniques for gravimetric geoid computation. The Land Levelling Datum (LLD) is the South African vertical datum based on more than 100 years old tide gauge measurements of mean sea level (MSL). The LLD is poorly defined so an alternative is required. The SAGEOID10 (Merry, …
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Three-Dimensional Spherical Modeling of the Mantles of Mars and Ceres: Inference from Geoid, Topography and Melt History
… structure in the mantle contributes to the geoid and topography on the planet. I also analyze how much of the internal density contributes to the surface topography and areoid of Mars. In contrast to Mars, Ceres is a dwarf planet in the Asteroid belt. Ceres is an icy body and it is unclear …
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Lateral variation in upper mantle temperature and composition beneath mid-ocean ridges inferred from shear-wave propagation, geoid, and bathymetry
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.
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Application of Seasat altimetry to tectonic studies of fracture zones in the Southern oceans
… In the first study, the correlation between the geoid, deflection of the vertical, and seafloor topography is investigated along a section of the Southwest Indian Ridge. Geoid anomalies computed from a simple thermal model fairly accurately predict the intermediate-wavelength anomalies across the …
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The oceanographic and geoidal components of sea surface topography
… circulation (ζ) and to estimate the marine geoid (γ), both in the wavelength band 100 km-2000 km. Optimum inverse methods in geophysics are reviewed. They are then used to analyze the estimation of the geoid from gravity data, emphasizing the wavenumber spectrum of resolution functions. It …
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Splines and local approximation of the earth's gravity field
… as least squares collocation in representing geoid heights or gravity anomalies. A pseudo-cubic spline geoid for southern Africa is given, interpolating Doppler-derived geoid heights and astro-geodetic deflections of the vertical. Quadrature rules are derived for the thin-plate spline …
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The effect of a shallow low viscosity zone on mantle convection and its expression at the surface of the earth
… and the observation of small scale (150-250 km) geoid and topography anomalies in the Central Pacific and Indian oceans. Convective models are presented of the formation and evolution of these features. In particular, the effect of a shallow low viscosity layer in the uppermost mantle on mantle …
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Satellite borne radar altimetry : empirical orbit refinement and ocean signal recovery techniques
… TOPEX/Poseidon errors. The extraction of marine geoid information is of great interest to the oceanographic community and was the subject of the second half of this thesis. Firstly through determination of regional mean sea surfaces using Geosat data, it was demonstrated that a dataset with 70cm …
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The effect of a shallow low viscosity zone on mantle convection and its expression at the surface of the earth
… and the observation of small scale (150-250 km) geoid and topography anomalies in the Central Pacific and Indian oceans. Convective models are presented of the formation and evolution of these features. In particular, the effect of a shallow low viscosity layer in the uppermost mantle on mantle …
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Characterization of secondary mantle convection from geophysical data and models
… and models such as seismic tomography models and geoid anomalies. We used three seismic tomography models, SEMUCB-WM1, SAVANI and S40RTS to infer the lithosphere/asthenosphere boundary, and the destabilization of the lithosphere, induced by secondary mantle convection. Former studies, based on …
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The New Concept of GRACE Gradiometry and the Unravelling of the Mystery of Stripes
… are the result of oversampling the low frequency geoid along the east-west (latitudinal) direction. The low-frequency geoid modulates the total sampled gravitational signal with a frequency near (m/n)fs, where fs is the sampling frequency of the GRACE ground track bundles along the parallels, and …
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Effects Of Subduction History On Mantle Convection: Implications For True Polar Wander And Dynamic Topography
… predictions of True Polar Wander (TPW), the geoid, and dynamic topography to observations. We explicitly calculate past mantle states using TERRA forward global geodynamic models that assimilate two different global plate reconstructions: a widely used model we call ‘Earthbyte’ and a recently …
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Glacial isostatic adjustment and relative sea level change over the last earthquake cycle in upper Cook Inlet, Alaska, USA
… displacement and deformation of the ocean geoid at a series of locations in south central Alaska over the past 1000 years. Modelling results show the asthenosphere viscosity and thickness to be the main rheological controls on relative displacement during the last earthquake deformation …
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Global isotopic signatures of oceanic island basalts
… both models, correlate well with the degree 2 geoid, indicating a deep origin for the components since the degrees 2-3 geoid is in ferred to result from topography at the core-mantle boundary. The DUPAL and DMM components, for both models, correlate well [and negati vely! at degree 3 with the …
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Global isotopic signatures of oceanic island basalts / by
… both models, correlate well with the degree 2 geoid, indicating a deep origin for the components since the degrees 2-3 geoid is inferred to result from topography at the core-mantle boundary. The DUPAL and DMM components, for both models, correlate well [and negatively] at degree 3 with the …
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