Gravity Inversion

Sjöberg, Lars E.; Bagherbandi, Mohammad

doi:10.1007/978-3-319-50298-4_8

Cited by 5 publications

(4 citation statements)

References 146 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this strategy, the best-fitting GGM to the gravity field in the region contributes to the accuracy of the high-resolution geoid by improving the long-wavelength component in the error budget [27][28][29]. The GGM contribution to the regional geoid model accuracy can be even more crucial if there is a lack of high-quality and sufficiently dense terrestrial gravity data under certain modifications of the kernel function and when a few-centimeter accuracy geoid model is desired (see e.g., [30]). Regarding this issue, we evaluated the released GGMs in high-frequency geoid computations using gravity data in Turkey.…”

Section: Practical Need Of Global Geopotential Model Validation Resultsmentioning

confidence: 99%

“…In the computation of a regional geoid model with hybrid (mixed) data in RCR, the GGM is responsible for the long-wavelength (signal) error content (see Equations (10) and (11)). When calculating a geoid model over a spatially limited region, while having low-accuracy and sparse terrestrial data, the quality of the GGM becomes even more important to compensate for the weakness of the terrestrial data accordingly in the RCR algorithm with specific modifications [30,67].…”

Section: Ggms' Contribution In High-resolution Regional Geoid Modelingmentioning

confidence: 99%

See 1 more Smart Citation

An Assessment of the GOCE High-Level Processing Facility (HPF) Released Global Geopotential Models with Regional Test Results in Turkey

2020

View full text Add to dashboard Cite

The launch of dedicated satellite missions at the beginning of the 2000s led to significant improvement in the determination of Earth gravity field models. As a consequence of this progress, both the accuracies and the spatial resolutions of the global geopotential models increased. However, the spectral behaviors and the accuracies of the released models vary mainly depending on their computation strategies. These strategies are briefly explained in this article. Comprehensive quality assessment of the gravity field models by means of spectral and statistical analyses provides a comparison of the gravity field mapping accuracies of these models, as well as providing an understanding of their progress. The practical benefit of these assessments by means of choosing an optimal model with the highest accuracy and best resolution for a specific application is obvious for a broad range of geoscience applications, including geodesy and geophysics, that employ Earth gravity field parameters in their studies. From this perspective, this study aims to evaluate the GOCE High-Level Processing Facility geopotential models including recently published sixth releases using different validation methods recommended in the literature, and investigate their performances comparatively and in addition to some other models, such as GOCO05S, GOGRA04S and EGM2008. In addition to the validation statistics from various countries, the study specifically emphasizes the numerical test results in Turkey. It is concluded that the performance improves from the first generation RL01 models toward the final RL05 models, which were based on the entire mission data. This outcome was confirmed when the releases of different computation approaches were considered. The accuracies of the RL05 models were found to be similar to GOCO05S, GOGRA04S and even to RL06 versions but better than EGM2008, in their maximum expansion degrees. Regarding the results obtained from these tests using the GPS/leveling observations in Turkey, the contribution of the GOCE data to the models was significant, especially between the expansion degrees of 100 and 250. In the study, the tested geopotential models were also considered for detailed geoid modeling using the remove-compute-restore method. It was found that the best-fitting geopotential model with its optimal expansion degree (please see the definition of optimal degree in the article) improved the high-frequency regional geoid model accuracy by almost 15%.

show abstract

Section: Practical Need Of Global Geopotential Model Validation Resultsmentioning

confidence: 99%

Section: Ggms' Contribution In High-resolution Regional Geoid Modelingmentioning

confidence: 99%

An Assessment of the GOCE High-Level Processing Facility (HPF) Released Global Geopotential Models with Regional Test Results in Turkey

2020

View full text Add to dashboard Cite

show abstract

“…The intensity of gravity is very valuable in various applications. It plays a crucial role [17,18] in detecting seismic faults, estimating simple spherical structures within the Earth, determining geoid and quasi-geoid (which define the physical shape of the Earth and reference surface of physical heights), [19] analyzing sea surface topography, understanding the structure of the lithosphere, inferring the thickness of floating ice, and [20] even detecting archaeological structures during exploration.…”

Section: Introductionmentioning

confidence: 99%

A G-Modified Helmholtz Equation with New Expansions for the Earth’s Disturbing Gravitational Potential, Its Functionals and the Study of Isogravitational Surfaces

Manoussakis

2024

AppliedMath

View full text Add to dashboard Cite

The G-modified Helmholtz equation is a partial differential equation that enables us to express gravity intensity g as a series of spherical harmonics having radial distance r in irrational powers. The Laplace equation in three-dimensional space (in Cartesian coordinates, is the sum of the second-order partial derivatives of the unknown quantity equal to zero) is used to express the Earth’s gravity potential (disturbing and normal potential) in order to represent other useful quantities—which are also known as functionals of the disturbing potential—such as gravity disturbance, gravity anomaly, and geoid undulation as a series of spherical harmonics. We demonstrate that by using the G-modified Helmholtz equation, not only gravity intensity but also disturbing potential and its functionals can be expressed as a series of spherical harmonics. Having gravity intensity represented as a series of spherical harmonics allows us to create new Global Gravity Models. Furthermore, a more detailed examination of the Earth’s isogravitational surfaces is conducted. Finally, we tabulate our results, which makes it clear that new Global Gravity Models for gravity intensity g will be very useful for many geophysical and geodetic applications.

show abstract

“…Nolet 2008 ; Tromp 2019 ), gravitational (e.g. Sjöberg & Bagherbandi 2017 ) and electromagnetic (e.g. Tikhonov 1950 ; Chave & Jones 2012 ) fields, as well as its response to deformation by both internal (e.g.…”

Section: Introductionmentioning

confidence: 99%

GIA imaging of 3-D mantle viscosity based on palaeo sea level observations – Part I: Sensitivity kernels for an Earth with laterally varying viscosity

Lloyd,

Crawford,

Al-Attar

et al. 2023

Geophysical Journal International

View full text Add to dashboard Cite

SUMMARY A key initial step in geophysical imaging is to devise an effective means of mapping the sensitivity of an observation to the model parameters, that is to compute its Fréchet derivatives or sensitivity kernel. In the absence of any simplifying assumptions and when faced with a large number of free parameters, the adjoint method can be an effective and efficient approach to calculating Fréchet derivatives and requires just two numerical simulations. In the Glacial Isostatic Adjustment problem, these consist of a forward simulation driven by changes in ice mass and an adjoint simulation driven by fictitious loads that are applied at the observation sites. The theoretical basis for this approach has seen considerable development over the last decade. Here, we present the final elements needed to image 3-D mantle viscosity using a dataset of palaeo sea-level observations. Developments include the calculation of viscosity Fréchet derivatives (i.e. sensitivity kernels) for relative sea-level observations, a modification to the numerical implementation of the forward and adjoint problem that permits application to 3-D viscosity structure, and a recalibration of initial sea level that ensures the forward simulation honours present-day topography. In the process of addressing these items, we build intuition concerning how absolute sea-level and relative sea-level observations sense Earth’s viscosity structure and the physical processes involved. We discuss examples for potential observations located in the near field (Andenes, Norway), far field (Seychelles), and edge of the forebulge of the Laurentide ice sheet (Barbados). Examination of these kernels: (1) reveals why 1-D estimates of mantle viscosity from far-field relative sea-level observations can be biased; (2) hints at why an appropriate differential relative sea-level observation can provide a better constraint on local mantle viscosity and (3) demonstrates that sea-level observations have non-negligible 3-D sensitivity to deep mantle viscosity structure, which is counter to the intuition gained from 1-D radial viscosity Fréchet derivatives. Finally, we explore the influence of lateral variations in viscosity on relative sea-level observations in the Amundsen Sea Embayment and at Barbados. These predictions are based on a new global 3-D viscosity inference derived from the shear-wave speeds of GLAD-M25 and an inverse calibration scheme that ensures compatibility with certain fundamental geophysical observations. Use of the 3-D viscosity inference leads to: (1) generally greater complexity within the kernel; (2) an increase in sensitivity and presence of shorter length-scale features within lower viscosity regions; (3) a zeroing out of the sensitivity kernel within high-viscosity regions where elastic deformation dominates and (4) shifting of sensitivity at a given depth towards distal regions of weaker viscosity. The tools and intuition built here provide the necessary framework to explore inversions for 3-D mantle viscosity based on palaeo sea-level data.

show abstract

Gravity Inversion

Cited by 5 publications

References 146 publications

An Assessment of the GOCE High-Level Processing Facility (HPF) Released Global Geopotential Models with Regional Test Results in Turkey

An Assessment of the GOCE High-Level Processing Facility (HPF) Released Global Geopotential Models with Regional Test Results in Turkey

A G-Modified Helmholtz Equation with New Expansions for the Earth’s Disturbing Gravitational Potential, Its Functionals and the Study of Isogravitational Surfaces

GIA imaging of 3-D mantle viscosity based on palaeo sea level observations – Part I: Sensitivity kernels for an Earth with laterally varying viscosity

Contact Info

Product

Resources

About