Probabilistic linear inversion of satellite gravity gradient data applied to the northeast Atlantic

The Wilkes Subglacial Basin (WSB) is a major intraplate tectonic feature in East Antarctica. It stretches for ca 1400 km from the edge of the Southern Ocean, where it is up to 600 km wide towards South Pole, where it is less than 100 km wide. Recent modelling of its subice topography (Paxman et al., 2019, JGR) lends support to a long-standing hypothesis predicting that the wide basin is linked to flexure of more rigid and mostly Precambrian cratonic lithosphere induced by the Cenozoic uplift of the adjacent Trasantarctic Mountains,. However, there is also mounting evidence from potential field and radar exploration that its narrower structurally controlled sub-basins may have formed in response to more localised Mesozoic to Cenozoic extension and transtension that preferentially steered glacial erosion (Paxman et al., 2018, GRL). &#160;Here we exploit recent advancements in regional aerogeophysical data compilations and continental scale satellite gravity gradient imaging with the overarching aim of helping unveil the degree of 4D heterogeneity in the crust and lithosphere beneath the WSB. New views of crustal and lithosphere thickness stem from 3D satellite gravity modelling (Pappa et al., 2019, JGR) and these can be compared with predictions from previous flexural modelling and seismological results. By stripping out the computed effects of crustal and lithosphere thickness variations we then obtain residual intra-crustal gravity anomalies. These are in turn compared with a suite of enhanced aeromagnetic anomaly images. We then calculate depth to magnetic and gravity source estimates and use these results to help constrain the first combined 2D magnetic and gravity models for two selected regions within the WSB.One first model reveals a major lithospheric scale boundary along the eastern margin of the northern WSB. It separates the Cambro-Ordovician Ross Orogen from a newly defined composite Precambrian Wilkes Terrane that forms the unexposed crustal basement buried beneath partially exposed early Cambrian metasediments and more recent Devonian to Jurassic sediments.Our second model investigates a sector of the WSB further south, where the proposed Precambrian basement is modelled as being both shallower and of more felsic bulk composition. Although the lack of drilling precludes direct sampling of this cryptic basement, aeromagnetic anomaly patterns suggest that it may be akin to late Paleoproterozoic to Mesoproterozoic igneous basement exposed in part of the Gawler and Curnamona cratons in South Australia. We conclude that these first order differences in basement depth, bulk composition and thickness of metasediment/sediment cover are a key and previously un-appreciated intra-crustal boundary condition, which is likely to affect geothermal heat flux variability beneath different sectors of the WSB, with potential cascading effects on subglacial hydrology and the flow of the overlying East Antarctic Ice Sheet.

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Sequential inversion of GOCE satellite gravity gradient data and terrestrial gravity data for the lithospheric density structure in the North China Craton

Solid Earth ◽

10.5194/se-11-1121-2020 ◽

2020 ◽

Vol 11 (3) ◽

pp. 1121-1144

Author(s):

Yu Tian ◽

Yong Wang

Keyword(s):

North China ◽

Gravity Data ◽

Initial Density ◽

Gravity Gradient ◽

Density Structure ◽

Satellite Gravity ◽

Density Data ◽

The North ◽

Density Anomaly ◽

Goce Satellite

Abstract. The North China Craton (NCC) is one of the oldest cratons in the world. Currently, the destruction mechanism and geodynamics of the NCC remain controversial. All of the proposed views regarding the issues involve studying the internal density structure of the NCC lithosphere. Gravity field data are among the most important data in regard to investigating the lithospheric density structure, and gravity gradient data and gravity data each possess their own advantages. Given the different observational plane heights between the on-orbit GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) satellite gravity gradient and terrestrial gravity and the effects of the initial density model on the inversion results, sequential inversion of the gravity gradient and gravity are divided into two integrated processes. By using the preconditioned conjugate gradient (PCG) inversion algorithm, the density data are calculated using the preprocessed corrected gravity anomaly data. Then, the newly obtained high-resolution density data are used as the initial density model, which can serve as constraints for the subsequent gravity gradient inversion. Several essential corrections are applied to the four gravity gradient tensors (Txx, Txz, Tyy, Tzz) of the GOCE satellite, after which the corrected gravity gradient anomalies (T′xx, T′xz, T′yy, T′zz) are used as observations. The lithospheric density distribution result within the depth range of 0–180 km in the NCC is obtained. This study clearly illustrates that GOCE data are helpful in understanding the geological settings and tectonic structures in the NCC with regional scale. The inversion results show that in the crust the eastern NCC is affected by lithospheric thinning with obvious local features. In the mantle, the presented obvious negative-density areas are mainly affected by the high-heat-flux environment. In the eastern NCC, the density anomaly in the Bohai Bay area is mostly attributed to the extension of the Tancheng–Lujiang major fault at the eastern boundary. In the western NCC, the crustal density anomaly distribution of the Qilian block is consistent with the northwest–southeast strike of the surface fault belt, whereas such an anomaly distribution experiences a clockwise rotation to a nearly north–south direction upon entering the mantle.

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Joint inversion of the lithospheric density struture in the North China Craton based on GOCE satellite gravity gradient data and surface gravity data

10.5194/egusphere-egu2020-3977 ◽

2020 ◽

Author(s):

Yu Tian ◽

Yong Wang

Keyword(s):

North China ◽

Joint Inversion ◽

Gravity Data ◽

Initial Density ◽

Gravity Gradient ◽

Density Structure ◽

Satellite Gravity ◽

Density Data ◽

The North ◽

Goce Satellite

The North China Craton (NCC) is one of the oldest cratons in the world. Currently, the destruction mechanism and geodynamics of the NCC still remain controversial. All of the proposed views regarding the issues involve studying the internal density structure of the NCC lithosphere. Gravity field data are one of the most important data in regard to investigating the lithospheric density structure, the gravity gradient data and the gravity data possess their own advantages. Given the inconsistency of the on orbit GOCE satellite gravity gradient and surface gravity observation plane height, also effects of the initial density model upon of the inversion results, the joint inversion of gravity gradient and gravity are divided into two integrated processes. By using the preconditioned conjugate gradient (PCG) inversion algorithm, the density data are calculated using the preprocessed remaining gravity anomaly data. The newly obtained high resolution density data are then used as the initial density model, which can be served as the constraints for the subsequent gravity gradient inversion. Downward continuation, terrain correction, interface undulation correction and long wavelength correction are performed for the four gravity gradient tensor data(Txx&#65292;Txz&#65292;Tyy&#65292;Tzz)of the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite, &#160;after which the remaining gravity gradient anomaly data(T'xx&#65292;T'xz&#65292;T'yy&#65292;T'zz) are used as the new observation quantity. Finally, the ultimate lithospheric density distribution within the depth range of 0&#8211;180 km in the NCC is obtained using the same PCG algorithm.

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The role of a laterally varying density contrast for gravity inversion of the Moho depth

10.5194/egusphere-egu2020-7145 ◽

2020 ◽

Author(s):

Peter Haas ◽

Joerg Ebbing ◽

Wolfgang Szwillus ◽

Philipp Tabelow

Keyword(s):

Global Scale ◽

Density Contrast ◽

Gradient Field ◽

Moho Depth ◽

Gravity Gradient ◽

Gravity Inversion ◽

Gravity Gradients ◽

Regional Study ◽

Satellite Gravity ◽

Amazonian Craton

We present a new inverse approach to invert satellite gravity gradients for the Moho depth under consideration of a laterally varying density contrast between crust and mantle. The inverse problem is linearized and solved with the classical Gauss-Newton algorithm in a spherical geometry. To ensure stable solutions, the Jacobian is smoothed with second-order Tikhonov regularization. During the inversion, the Moho depth is discretized into tesseroids by reference Moho depth and density contrast, from which the gravitational effect can be calculated. As a computational benefit, the Jacobian is calculated only once and afterwards weighted with the laterally varying density contrast. We look for a Moho depth model that simultaneously explains the gravity gradient field and a least misfit to existing seismic Moho depth determinations. We perform the inversion both on regional and global scale.The laterally varying density contrast is based on different tectonic units, which are defined by independent global geological and geophysical data, such as regionalization of dispersion curves. This is beneficial in remote areas, where seismic investigations are very sparse and the crustal structure is to a large extent unknown. Applying the inversion to the Amazonian Craton and its surroundings shows a lower density contrast at the Moho depth for the continental interior compared to oceanic domains. This is in accordance with the tectono-thermal architecture of the lithosphere. The inverted values of the density vary between 300-450 kg/m3. The inverted Moho depth shows a clear separation between the Sao Francisco Craton and shallower Amazonian Craton.Gravity inversion with a laterally varying density contrast requires a uniform reference Moho depth. On a global scale, we utilize our inversion to estimate a reference Moho depth that is in accordance with crustal buoyancy. The inverted density contrasts show a similar trend like the regional study area. The inverted Moho depth shows expected tectonic features. Our method of computing the Jacobian once and weighting with lateral variable density contrasts is a valuable optimization of standard gravity inversion.

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Gravity Anomaly Computed by GOCE Data in Northeastern Margin of Tibetan Plateau

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.117-119.1461 ◽

2011 ◽

Vol 117-119 ◽

pp. 1461-1464

Author(s):

Hai Jun Xu ◽

Yong Zhi Zhang ◽

Hu Rong Duan

Keyword(s):

Tibetan Plateau ◽

Gravity Anomaly ◽

Gravity Gradient ◽

Gravity Gradiometry ◽

Satellite Gravity Gradiometry ◽

Satellite Gravity ◽

Strong Earthquakes ◽

Gradient Zone ◽

Regional Tectonic ◽

Goce Satellite

In this paper, gravity anomaly in northeastern margin of Tibetan Plateau (90ºand 110º E, 28ºand 42º N) is computed using satellite gravity gradiometry data from GOCE satellite. The computed gravity anomaly is compared with the topographical data and location of some strong earthquakes in this region. The result shows that gravity anomaly has good conformity with the regional tectonic distribution and strong earthquake usually occurred in the steep gravity gradient zone.

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