Analysis of the Topography and Gravity Data for the Earth-like Venus

Lake water height is a key variable in water cycle and climate change studies, which is achievable using satellite altimetry constellation. A method based on data processing of altimetry from several satellites has been developed to interpolate mean lake surface (MLS) over a set of 22 big lakes distributed on the Earth. It has been applied on nadir radar altimeters in Low Resolution Mode (LRM: Jason-3, Saral/AltiKa, CryoSat-2) in Synthetic Aperture Radar (SAR) mode (Sentinel-3A), and in SAR interferometric (SARin) mode (CryoSat-2), and on laser altimetry (ICESat). Validation of the method has been performed using a set of kinematic GPS height profiles from 18 field campaigns over the lake Issykkul, by comparison of altimetry&#8217;s height at crossover points for the other lakes and using the laser altimetry on ICESat-2 mission. The precision reached ranges from 3 to 7 cm RMS (Root Mean Square) depending on the lakes. Currently, lake water level inferred from satellite altimetry is provided with respect to an ellipsoid. Ellipsoidal heights are converted into orthom&#233;tric heights using geoid models interpolated along the satellite tracks. These global geoid models were inferred from geodetic satellite missions coupled with absolute and regional anomaly gravity data sets spread over the Earth. However, the spatial resolution of the current geoid models does not allow capturing short wavelength undulations that may reach decimeters in mountaineering regions or for rift lakes (Baikal, Issykkul, Malawi, Tanganika). We interpolate in this work the geoid height anomalies with three recent geoid models, the EGM2008, XGM2016 and EIGEN-6C4d, and compare them with the Mean Surface of 22 lakes calculated using satellite altimetry. Assuming that MLS mimics the local undulations of the geoid, our study shows that over a large set of lakes (in East Africa, Andean mountain and Central Asia), short wavelength undulations of the geoid in poorly sampled areas can be derived using satellite altimetry. The models used in this study present very similar geographical patterns when compared to MLS. The precision of the models largely depends on the location of the lakes and is about 18 cm, in average over the Earth. MLS can serve as a validation dataset for any future geoid model. It will also be useful for validation of the future mission SWOT (Surface Water and Ocean Topography) which will measure and map water heights over the lakes with a high horizontal resolution of 250 by 250 meters.

Download Full-text

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

Earth Science Research ◽

10.5539/esr.v7n1p94 ◽

2018 ◽

Vol 7 (1) ◽

pp. 94

Author(s):

Anatole Eugene Djieto Lordon ◽

Mbohlieu YOSSA ◽

Christopher M Agyingi ◽

Yves Shandini ◽

Thierry Stephane Kuisseu

Keyword(s):

Average Length ◽

Gravity Data ◽

Bouguer Anomaly ◽

Igneous Rocks ◽

Average Depth ◽

The Earth ◽

Gravitational Model ◽

Petroleum Generation ◽

Anomaly Map ◽

Bouguer Anomaly Map

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.

Download Full-text

Accuracy Analysis of Gravity Field Changes from Grace RL06 and RL05 Data Compared to in Situ Gravimetric Measurements in the Context of Choosing Optimal Filtering Type

Artificial Satellites ◽

10.2478/arsa-2020-0008 ◽

2020 ◽

Vol 55 (3) ◽

pp. 100-117

Author(s):

Viktor Szabó ◽

Dorota Marjańska

Keyword(s):

Gravity Field ◽

Ocean Circulation ◽

Gravity Data ◽

The Other ◽

Subsurface Water ◽

Satellite Gravity ◽

Absolute Gravimetry ◽

The Earth ◽

Gravity Measurements ◽

Gravity Recovery

AbstractGlobal satellite gravity measurements provide unique information regarding gravity field distribution and its variability on the Earth. The main cause of gravity changes is the mass transportation within the Earth, appearing as, e.g. dynamic fluctuations in hydrology, glaciology, oceanology, meteorology and the lithosphere. This phenomenon has become more comprehensible thanks to the dedicated gravimetric missions such as Gravity Recovery and Climate Experiment (GRACE), Challenging Minisatellite Payload (CHAMP) and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE). From among these missions, GRACE seems to be the most dominating source of gravity data, sharing a unique set of observations from over 15 years. The results of this experiment are often of interest to geodesists and geophysicists due to its high compatibility with the other methods of gravity measurements, especially absolute gravimetry. Direct validation of gravity field solutions is crucial as it can provide conclusions concerning forecasts of subsurface water changes. The aim of this work is to present the issue of selection of filtration parameters for monthly gravity field solutions in RL06 and RL05 releases and then to compare them to a time series of absolute gravimetric data conducted in quasi-monthly measurements in Astro-Geodetic Observatory in Józefosław (Poland). The other purpose of this study is to estimate the accuracy of GRACE temporal solutions in comparison with absolute terrestrial gravimetry data and making an attempt to indicate the significance of differences between solutions using various types of filtration (DDK, Gaussian) from selected research centres.

Download Full-text

Evaluation of Gravity Data Derived from Global Gravity Field Models Using Terrestrial Gravity Data in Enugu State, Nigeria

Journal of Geodetic Science ◽

10.1515/jogs-2018-0015 ◽

2018 ◽

Vol 8 (1) ◽

pp. 145-153 ◽

Cited By ~ 2

Author(s):

O.I. Apeh ◽

E.C. Moka ◽

V.N. Uzodinma

Keyword(s):

Gravity Field ◽

Gravity Data ◽

Gravity Anomalies ◽

Mean Square ◽

Bouguer Gravity ◽

Bouguer Anomalies ◽

The Earth ◽

Global Gravity ◽

Enugu State ◽

Gravity Field Models

Abstract Spherical harmonic expansion is a commonly applied mathematical representation of the earth’s gravity field. This representation is implied by the potential coeffcients determined by using elements/parameters of the field observed on the surface of the earth and/or in space outside the earth in the spherical harmonic expansion of the field. International Centre for Gravity Earth Models (ICGEM) publishes, from time to time, Global Gravity Field Models (GGMs) that have been developed. These GGMs need evaluation with terrestrial data of different locations to ascertain their accuracy for application in those locations. In this study, Bouguer gravity anomalies derived from a total of eleven (11) recent GGMs, using sixty sample points, were evaluated by means of Root-Mean-Square difference and correlation coeficient. The Root-Mean-Square differences of the computed Bouguer anomalies from ICGEMwebsite compared to their positionally corresponding terrestrial Bouguer anomalies range from 9.530mgal to 37.113mgal. Additionally, the correlation coe_cients of the structure of the signal of the terrestrial and GGM-derived Bouguer anomalies range from 0.480 to 0.879. It was observed that GECO derived Bouguer gravity anomalies have the best signal structure relationship with the terrestrial data than the other ten GGMs. We also discovered that EIGEN-6C4 and GECO derived Bouguer anomalies have enormous potential to be used as supplements to the terrestrial Bouguer anomalies for Enugu State, Nigeria.

Download Full-text

Unraveling the upper mantle heterogeneity from integrated multi-observable inversions

10.5194/egusphere-egu2020-2685 ◽

2020 ◽

Author(s):

Javier Fullea ◽

Sergei Lebedev ◽

Zdenek Martinec ◽

Nicolas Celli

Keyword(s):

Seismic Tomography ◽

Upper Mantle ◽

Plate Tectonics ◽

Seismic Velocity ◽

Gravity Data ◽

Density Field ◽

Seismic Velocities ◽

Satellite Gravity ◽

The Earth ◽

Multiple Data Sets

The lateral and vertical thermochemical heterogeneity in the mantle is a long standing question in geodynamics. The forces that control mantle flow and therefore Plate Tectonics arise from the density and viscosity lateral and vertical variations. A common approach to estimate the density field for geodynamical purposes is to simply convert seismic tomography anomalies sometimes assuming constraints from mineral physics. Such converted density field does not match in general with the observed gravity field, typically predicting anomalies the amplitudes of which are too large. Knowledge on the lateral variations in lithospheric density is essential to understand the dynamic/residual isostatic components of the Earth&#8217;s topography linking deep and surface processes. The cooling of oceanic lithosphere, the bathymetry of mid oceanic ridges, the buoyancy and stability of continental cratons or the thermochemical structure of mantle plumes are all features central to Plate Tectonics that are dramatically related to mantle temperature and composition. Conventional methods of seismic tomography, topography and gravity data analysis constrain distributions of seismic velocity and density at depth, all depending on temperature and composition of the rocks within the Earth. However, modelling and interpretation of multiple data sets provide a multifaceted image of the true thermochemical structure of the Earth that needs to be appropriately and consistently integrated. A simple combination of gravity, petrological and seismic models alone is insufficient due to the non-uniqueness and different sensitivities of these models, and the internal consistency relationships that must connect all the intermediate parameters describing the Earth involved. In fact, global Earth models based on different observables often lead to rather different, even contradictory images of the Earth. &#160;Here we present a new global thermochemical model of the lithosphere-upper mantle (WINTERC-grav) constrained by state-of-the-art global waveform tomography, satellite gravity (geoid and gravity anomalies and gradiometric measurements from ESA's GOCE mission), surface elevation and heat flow data. WINTERC-grav is based upon an integrated geophysical-petrological approach where all relevant rock physical properties modelled (seismic velocities and density) are computed within a thermodynamically self-consistent framework allowing for a direct parameterization of the temperature and composition variables.

Download Full-text

On accurate geoid modeling: derivation of dirichlet problems that govern geoidal undulations and geoid modeling by means of the finite difference method and a hybrid method

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702014000200020 ◽

2014 ◽

Vol 20 (2) ◽

pp. 334-353

Author(s):

Eduardo Del Rio

Keyword(s):

Dirichlet Problem ◽

Finite Difference ◽

Finite Difference Method ◽

Hybrid Method ◽

Difference Method ◽

Gravity Data ◽

Dirichlet Problems ◽

Geoid Model ◽

The Earth ◽

Stokes's Integral

The geoid is the reference surface used to measure heights (orthometric). These are used to study any mass variability in the Earth system. As the Earth is represented by an oblate spheroid (Ellipsoid), the geoid is determined by geoidal undulations (N) which are the separation between these surfaces. N is determined from gravity data by Stokes's Integral. However, this approach takes a Spherical rather than an Ellipsoidal Earth. Here it is derived a Partial Differential Equation (PDE) that governs N over the Earth by means of a Dirichlet problem and show a method to solve it which precludes the need for a Spherical Earth. Moreover, Stokes's Integral solves a boundary value problem defined over the whole Earth. It was found that the Dirichlet problem derived here is defined only over the region where a geoid model is to be computed, which is advantageous for local geoid modeling. Moreover, the method eliminates several of the sources of uncertainty in Stokes's Integral. However, estimates indicate that the errors due to discretization are very large in this new method which calls for its modification. So, here it is also proposed an optimal combination of techniques by means of a Hybrid method and shown that it alleviates the uncertainty in Finite Difference Method. Moreover, a rigorous error analysis indicates that the Hybrid method proposed here may well outperform Stokes's Integral.

Download Full-text

Interpretation of gravity data derived from the Earth Gravitational Model EGM2008 in the Center-North Cameroon: structural and mining implications

Arabian Journal of Geosciences ◽

10.1007/s12517-017-2919-y ◽

2017 ◽

Vol 10 (6) ◽

Cited By ~ 4

Author(s):

Jean Marcel Abate Essi ◽

Jean Marcel ◽

Joseph Quentin Yene Atangana ◽

Ahmad Diab Ahmad ◽

Elisabeth Fita Dassou ◽

...

Keyword(s):

Gravity Data ◽

The Earth ◽

Gravitational Model

Download Full-text

Estimation of the Depth of Major Subsurface Discontinuities Beneath the Mount Cameroon Region, Central Africa, Based on New and Existing Gravity Data Analysis

Earth Science Research ◽

10.5539/esr.v6n1p142 ◽

2017 ◽

Vol 6 (1) ◽

pp. 142

Author(s):

KENFACK Jean Victor ◽

Kamguia Joseph ◽

Kagou Dongmo Armand ◽

Kengni Lucas ◽

Mbog Michel Bertrand ◽

...

Keyword(s):

Spectral Analysis ◽

Data Analysis ◽

Gravity Data ◽

Bouguer Anomaly ◽

Central Africa ◽

Wave Number ◽

Earth History ◽

The Third ◽

Mount Cameroon ◽

The Earth

The Mount Cameroon region is investigated using 2-D spectral analysis of the gravity data, in order to determine the depth of subsurface interfaces beneath the region. New gravity data are combined to existing ones to determine the depth of the major subsurface discontinuities throughout the region. Depths are established from the slope of the log-power radial spectrum et the lower end of the wave number band. Three major subsurface density discontinuities are determined beneath the Mount Cameroon: (1) 0.41 ± 0.02 km, (2) 1.26 ± 0.06 km, (3) 4.73 ± 0.24 km. This result has the best precision comparing with the those from the former Bouguer anomaly where the major subsurface discontinuities obtained are: (1) 0.48 ± 0.02 km for the first layer, 1.81 ± 0.09 km for the second and 6.87 ± 0.34 km for the third. This difference is probabely due to the densification of gravity data. The knowledge on the depth of different interfaces in the crust is very important in the reconstitution of the earth history. These results will the support of prospective investigations throughout this region.

Download Full-text

GRACE—Gravity Data for Understanding the Deep Earth’s Interior

Remote Sensing ◽

10.3390/rs12244186 ◽

2020 ◽

Vol 12 (24) ◽

pp. 4186

Author(s):

Mioara Mandea ◽

Véronique Dehant ◽

Anny Cazenave

Keyword(s):

Gravity Data ◽

Outer Core ◽

Space Mission ◽

Last Deglaciation ◽

Mantle Boundary ◽

Core Mantle Boundary ◽

The Core ◽

Isostatic Adjustment ◽

The Earth ◽

Fluid Core

While the main causes of the temporal gravity variations observed by the Gravity Recovery and Climate Experiment (GRACE) space mission result from water mass redistributions occurring at the surface of the Earth in response to climatic and anthropogenic forces (e.g., changes in land hydrology, ocean mass, and mass of glaciers and ice sheets), solid Earth’s mass redistributions were also recorded by these observations. This is the case, in particular, for the glacial isostatic adjustment (GIA) or the viscous response of the mantle to the last deglaciation. However, it has only recently been shown that the gravity data also contain the signature of flows inside the outer core and their effects on the core–mantle boundary (CMB). Detecting deep Earth’s processes in GRACE observations offers an exciting opportunity to provide additional insight into the dynamics of the core–mantle interface. Here, we present one aspect of the GRACEFUL (GRavimetry, mAgnetism and CorE Flow) project, i.e., the possibility to use gravity field data for understanding the dynamic processes inside the fluid core and core–mantle boundary of the Earth, beside that offered by the geomagnetic field variations.

Download Full-text

How isostasy explains continental rifting in East Africa?

10.5194/egusphere-egu2020-149 ◽

2020 ◽

Author(s):

Mohammad Bagherbandi ◽

Nureldin A. A. Gido

Keyword(s):

East Africa ◽

Rift Valley ◽

Plate Tectonics ◽

Gravity Data ◽

Density Contrast ◽

Earthquake Activity ◽

Continental Rifting ◽

The Earth ◽

Geodynamic Processes ◽

Thin Crust

The principle of isostasy plays an important role to understand the relation between different geodynamic processes. Although, it is difficult to find an exact method that delivers a complete image of the Earth structure. However, gravimetric methods are alternative to provide images of the interior of the Earth. The Earth&#8217;s crust parameters, i.e. crustal depth and crust-mantle density contrast, can reveal adequate information about the solid Earth system such as volcanic activity, earthquake and continental rifting. Hence, in this study, a combine Moho model using seismic and gravity data is determined to investigate the relationship between the isostatic state of the lithosphere and seismic activities in East Africa. Our results show that isostatic equilibrium and compensation states are closely correlated to the seismicity patterns in the study area. For example, several studies suggest that African superplume causes the rift valley, and consequently differences in crustal and mantle densities occur. This paper presents a method to determine the crustal thickness and crust-mantle density contrast and consequently one can observe low-density contrast (about 200 kg/m3 ) and thin crust (about 30 km) near the triple junction plate tectonics in East Africa (Afar Triangle), which confirms the state of overcompensation in the rift valley areas. Furthermore, the density structure of the lithosphere shows a large correlation with the earthquake activity, sub-crustal stress and volcanic distribution across East Africa.

Download Full-text