Identification of mantle and lithospheric components of the gravity field by isostatic gravity anomalies

The scope of this work is to showcase the BRAT (Broadview Radar Altimetry Toolbox) and GUT (GOCE User Toolbox) toolboxes.The Broadview Radar Altimetry Toolbox (BRAT) is a collection of tools designed to facilitate the processing of radar altimetry data from all previous and current altimetry missions, including Sentinel-3A L1 and L2 products. A tutorial is included providing plenty of use cases on Geodesy & Geophysics, Oceanography, Coastal Zone, Atmosphere, Wind & Waves, Hydrology, Land, Ice and Climate, which can also be consulted in &#160;http://www.altimetry.info/radar-altimetry-tutorial/.BRAT's last version (4.2.1) was released in June 2018. Based on the community feedback, the front-end has been further improved and simplified whereas the capability to use BRAT in conjunction with MATLAB/IDL or C/C++/Python/Fortran, allowing users to obtain desired data bypassing the data-formatting hassle, remains unchanged. Several kinds of computations can be done within BRAT involving the combination of data fields, that can be saved for future uses, either by using embedded formulas including those from oceanographic altimetry, or by implementing ad-hoc Python modules created by users to meet their needs. BRAT can also be used to quickly visualise data, or to translate data into other formats, e.g. from NetCDF to raster images.The GOCE User Toolbox (GUT) is a compilation of tools for the use and the analysis of GOCE gravity field models. It facilitates using, viewing and post-processing GOCE L2 data and allows gravity field data, in conjunction and consistently with any other auxiliary data set, to be pre-processed by beginners in gravity field processing, for oceanographic and hydrologic as well as for solid earth applications at both regional and global scales. Hence, GUT facilitates the extensive use of data acquired during GRACE and GOCE missions.In the current version (3.2), GUT has been outfitted with a graphical user interface allowing users to visually program data processing workflows. Further enhancements aiming at facilitating the use of gradients, the anisotropic diffusive filtering, and the computation of Bouguer and isostatic gravity anomalies have been introduced. Packaged with GUT is also GUT's Variance/Covariance Matrix (VCM) tool, which enables non-experts to compute and study, with relative ease, the formal errors of quantities &#8211; such as geoid height, gravity anomaly/disturbance, radial gravity gradient, vertical deflections &#8211; that may be derived from the GOCE gravity models.On our continuous endeavour to provide better and more useful tools, we intend to integrate BRAT into SNAP (Sentinel Application Platform). This will allow our users to easily explore the synergies between both toolboxes. During 2020 we will start going from separate toolboxes to a single one.BRAT and GUT toolboxes can be freely downloaded, along with ancillary material, at https://earth.esa.int/brat and https://earth.esa.int/gut.

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On Gravity Inversion by No-Topography and Rigorous Isostatic Gravity Anomalies

Pure and Applied Geophysics ◽

10.1007/s00024-015-1032-y ◽

2015 ◽

Vol 172 (10) ◽

pp. 2669-2680 ◽

Cited By ~ 9

Author(s):

Lars E. Sjöberg ◽

Mohammad Bagherbandi ◽

Robert Tenzer

Keyword(s):

Gravity Anomalies ◽

Gravity Inversion ◽

Isostatic Gravity Anomalies ◽

Isostatic Gravity

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The edge of northwestern North America at ∼1.8 Ga

Canadian Journal of Earth Sciences ◽

10.1139/e05-039 ◽

2005 ◽

Vol 42 (6) ◽

pp. 983-997 ◽

Cited By ~ 18

Author(s):

Frederick A Cook ◽

Kevin W Hall ◽

C Elissa Lynn

Keyword(s):

Gravity Anomalies ◽

Western Canada Sedimentary Basin ◽

Bear Lake ◽

Lithospheric Extension ◽

Isostatic Gravity Anomalies ◽

Isostatic Gravity ◽

North American Craton ◽

Seismic Reflection Profiles ◽

Northwestern North America ◽

Canada Sedimentary Basin

The ∼1.80 Ga edge of the northwestern North American craton is buried beneath Phanerozoic and Proterozoic rocks of the Western Canada Sedimentary Basin and the adjacent Cordillera. It is visible in more than eight deep seismic reflection profiles that have images of west-facing crustal-scale monoclines with up to 1520 km of vertical relief, and it produces regional isostatic gravity anomalies that can be followed for more than 1500 km along strike. The deep reflection profiles include two major transects of Lithoprobe (southern Canadian Cordillera transect and Slave Northern Cordillera Lithospheric Evolution (SNORCLE) transect) and industry profiles that are strategically located to provide depth and geometry constraints on the monoclines. The isostatic anomalies mark the density transition from Paleoproterozoic and older crystalline rocks of the Canadian Shield to less dense supracrustal rocks of westward-thickening late Paleo proterozoic and younger strata. These gravity anomaly patterns thus provide areal geometry of crustal structure variations along strike away from the depth control provided by the seismic data. Although many of the monoclines follow the Fort Simpson geophysical trend along the Cordilleran deformation front, isostatic anomalies near Great Bear Lake delineate a northeast-striking region of low values that may coincide with a failed rift arm or the southern margin of a large basin. The monoclines are interpreted as a series of en echelon structures that probably formed as a result of lithospheric extension at about 1.801.70 Ga following terminal accretion of the Paleoproterozoic Wopmay Orogen.

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Using isostatic gravity anomalies from spherical harmonic models and elastic plate compensation to interpret the lithosphere of the Bolivian Andes

Geophysics ◽

10.1190/geo2012-0378.1 ◽

2013 ◽

Vol 78 (3) ◽

pp. G41-G53 ◽

Cited By ~ 3

Author(s):

Christopher Jekeli ◽

Hyo Jin Yang ◽

Kevin Ahlgren

Keyword(s):

Spherical Harmonic ◽

Flexural Rigidity ◽

Gravity Data ◽

Gravity Anomalies ◽

Surface Gravity ◽

Bolivian Andes ◽

Isostatic Gravity Anomalies ◽

Isostatic Gravity ◽

Spherical Harmonic Models ◽

Surface Gravity Data

We have determined for the Bolivian Andes that the new global gravity models derived from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission may be used directly to study lithospheric structure. Toward this end, we have formulated Bouguer and isostatic gravity anomalies in spherical approximation, rather than in the usual planar approach, using spherical harmonic series consistent with the satellite-derived gravitational models. From the approximate equivalency of topographic masses and surface density layers using the Helmert condensation method we further derived and used isotropic transfer relations between the spherical spectra of topographic loads and elastic spherical shell deflections, where the Airy isostatic compensation is the special case of no flexural rigidity. A numerical comparison of these spherical harmonic models to conventional three-dimensional modeling based on topographic data and newly acquired surface gravity data in Bolivia confirmed their suitability for lithospheric interpretation. Specifically, the relatively high and uniform resolution of the satellite gravitational model (better than 83 km) produces detailed maps of the isostatic anomaly that clearly delineate the flexure of the Brazilian shield that is thrust under the Sub-Andes. Inferred values of the thickness of Airy-type roots and the flexural rigidity of the elastic lithosphere agree reasonably with published results based on seismic and surface gravity data. In addition, a local minimum in the flexural rigidity is evident at the sharp bend of the eastern margins of the Sub-Andes in Bolivia. This feature is consistent with earlier theories for counter rotations about a vertical axis at this minimum, associated with the confluence of the subducted Nazca plate and the Brazilian craton. The GOCE model thus generates high-resolution isostatic anomaly maps that offer additional structural detail not seen as clearly from previous seismic and gravity investigations in this region.

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Geodynamic insights of the Cameroon Volcanic Line (Western Africa) from isostatic gravity anomalies

Journal of Geodynamics ◽

10.1016/j.jog.2018.07.002 ◽

2018 ◽

Vol 121 ◽

pp. 36-48 ◽

Cited By ~ 3

Author(s):

Jean Marcel ◽

Jean Marcel Abate Essi ◽

Jorelle Larissa Meli’i ◽

Philippe Njandjock Nouck ◽

Abakar Mahamat ◽

...

Keyword(s):

Gravity Anomalies ◽

Cameroon Volcanic Line ◽

Western Africa ◽

Isostatic Gravity Anomalies ◽

Isostatic Gravity

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Joint estimation of gravity anomalies using second and third order potential derivatives

Geophysical Journal International ◽

10.1093/gji/ggz517 ◽

2019 ◽

Author(s):

Mohsen Romeshkani ◽

Mohammad A Sharifi ◽

Dimitrios Tsoulis

Keyword(s):

Gravity Field ◽

Gravity Model ◽

Variance Component ◽

Gravity Anomalies ◽

Variance Component Estimation ◽

Third Order ◽

Global Gravity ◽

Isostatic Gravity ◽

Component Estimation ◽

Global Gravity Model

Abstract Satellite gradiometry data provide the framework for estimating and validating Earth's gravity field from second and third order derivatives of the Earth's gravitational potential. Such procedures are especially useful when applied locally, as they relate to local and regional characteristics of the real gravity field. In the present study a joint inversion procedure is proposed for the estimation of gravity anomalies at sea surface level from second and third order potential derivatives, based on a standard Gauss-Markov estimation model. The estimation procedure is applied for a test area stretching over Iran involving simulated grids from GOCE-only model GGM_TIM_R05 at GOCE altitude and gravity anomalies recovered at sea level. In order to validate the proposed estimation three different reductions have been considered independently, namely the removal of the long-wavelength part of the observed field through a global gravity model, the removal of the high-frequency part of the field through the incorporation of a topographic/isostatic gravity model and the application of variance component estimation. The application of a global gravity model leads to an improvement in the individual component estimation of the order of magnitude 3 per cent to 73 per cent, with a significant reduction in bias to 4 mGal. Smoother gradient components can come out according to removing the topography and taking into account for isostasy that improved up results of recovery to 25 per cent for the radial second order derivative. Finally, the implementation of variance component estimation leads to no significant improvement in results of recovered gravity anomalies.

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