3D Gravity Data Inversion for Estimating Shape of an Ore Body

2001 ◽  
Author(s):  
M. Mirzaei ◽  
H. Aasei
Keyword(s):  
Gravity Data ◽  
Data Inversion ◽  
Ore Body ◽  
3D Gravity

scholarly journals GRAV3D Validation using Generalized Cross-Validation (GCV) Algorithm by Lower Bounds Approach for 3D Gravity Data Inversion

2018 ◽  
Vol 5 (2) ◽  
pp. 271-277
Author(s):  
Mochamad Aryono Adhi ◽  
Wahyudi Wahyudi ◽  
Wiwit Suryanto ◽  
Muh Sarkowi
Keyword(s):  
Lower Bounds ◽  
Cross Validation ◽  
Gravity Data ◽  
3D Inversion ◽  
Generalized Cross Validation ◽  
Data Inversion ◽  
3D Gravity

The completion of gravitational data inversion results in a smooth recovered model. GRAV3D is one software that can be used to solve 3D inversion problems of gravity data. Nevertheless there are still fundamental problems related to how to ensure the validity of GRAV3D to be used in 3D inversion. One approach used is to use lower bounds as inversion parameters. In this study lower bounds are set from  to . The results obtained show that the use of lower bounds decreases resulting in a larger data misfit which means that the more data that meets the tolerance calculation, the better recovered model produced.

scholarly journals Disjoint interval bound constraints using the alternating direction method of multipliers (ADMM) for geologically constrained inversion: Application to gravity data

Geophysics ◽  
2020 ◽  
pp. 1-45
Author(s):  
Vitaliy Ogarko ◽  
Jérémie Giraud ◽  
Roland Martin ◽  
Mark Jessell
Keyword(s):  
Gravity Data ◽  
Alternating Direction Method ◽  
Rock Properties ◽  
Model Parameters ◽  
Method Of Multipliers ◽  
Geological Modeling ◽  
Bound Constraints ◽  
Data Inversion ◽  
Alternating Direction ◽  
Geological Information

To reduce uncertainties in reconstructed images, geological information must be introduced in a numerically robust and stable way during the geophysical data inversion procedure. In the context of potential (gravity) data inversion, it is important to bound the physical properties by providing probabilistic information on the number of lithologies and ranges of values of possibly existing related rock properties (densities). For this purpose, we introduce a generalization of bounding constraints for geophysical inversion based on the alternating direction method of multipliers (ADMM). The flexibility of the proposed technique enables us to take into account petrophysical information as well as probabilistic geological modeling, when it is available. The algorithm introduces a priori knowledge in terms of physically acceptable bounds of model parameters based on the nature of the modeled lithofacies in the region under study. Instead of introducing only one interval of geologically acceptable values for each parameter representing a set of rock properties, we define sets of disjoint intervals using the available geological information. Different sets of intervals are tested, such as quasi-discrete (or narrow) intervals as well as wider intervals provided by geological information obtained from probabilistic geological modeling. Narrower intervals can be used as soft constraints encouraging quasi-discrete inversions. The algorithm is first applied to a synthetic 2D case for proof-of-concept validation and then to the 3D inversion of gravity data collected in the Yerrida basin (Western Australia). Numerical convergence tests show the robustness and stability of the bound constraints we apply, which is not always trivial for constrained inversions. This technique can be a more reliable uncertainty reduction method as well as an alternative to other petrophysically or geologically constrained inversions based on more classical “clustering” or Gaussian-mixture approaches.

3D Gravity modeling of the volcanic island of Surtsey, Iceland

2021 ◽  
Author(s):  
sara sayyadi ◽  
Magnús T. Gudmundsson ◽  
Thórdís Högnadóttir ◽  
James White ◽  
Joaquín M.C. Belart ◽  
...  
Keyword(s):  
Sea Level ◽  
Gravity Data ◽  
Bouguer Anomaly ◽  
Gravity Modeling ◽  
Gravity Station ◽  
Effusive Activity ◽  
3D Gravity ◽  
Anomaly Map ◽  
Bouguer Anomaly Map ◽  
Drill Cores

<p>The formation of the oceanic island Surtsey in the shallow ocean off the south coast of Iceland in 1963-1967 remains one of the best-studied examples of basaltic emergent volcanism to date. The island was built by both explosive, phreatomagmatic phases and by effusive activity forming lava shields covering parts of the explosively formed tuff cones.  Constraints on the subsurface structure of Surtsey achieved mainly based on the documented evolution during eruption and from drill cores in 1979 and in the ICDP-supported SUSTAIN drilling expedition in 2017(an inclined hole, directed 35° from the vertical). The 2017 drilling confirmed the existence of a diatreme, cut into the sedimentary pre-eruption seafloor (Jackson et al., 2019). </p><p>We use 3D-gravity modeling, constrained by the stratigraphy from the drillholes to study the structure of the island and the underlying diatreme.  Detailed gravity data were obtained on Surtsey in July 2014 with a gravity station spacing of ~100 m. Density measurements for the seafloor sedimentary and tephra samples of the surface were carried out using the ASTM1 protocol. By comparing the results with specific gravity measurements of cores from drillhole in 2017, a density contrast of about 200 kg m<sup>-3</sup> was found between the lapilli tuffs of the diatreme and the seafloor sediments.  Our approach is to divide the island into four main units of distinct density: (1) tuffs above sea level, (2) tuffs below sea level, (3) lavas above sea level, and (4) a lava delta below sea level, composed of breccias over which the lava advanced during the effusive eruption.  The boundaries between the bodies are defined from the eruption history and mapping done during the eruption, aided by the drill cores. </p><p>A complete Bouguer anomaly map is obtained by calculating a total terrain correction by applying the Nagy formula to dense DEMs (5 m spacing out to 1.2 km from station, 200 m spacing between 1.2 km and 50 km) of both island topography and ocean bathymetry.  Through the application of both forward and inverse modeling, using the GM-SYS 3D software, the results provide a 3-D model of the island itself, as well as constraints on diatreme shape and depth.</p>

scholarly journals Integrated gradient interpretation techniques for 2D and 3D gravity data interpretation

2006 ◽  
Vol 58 (7) ◽  
pp. 815-821 ◽  
Author(s):  
Hakim Saibi ◽  
Jun Nishijima ◽  
Sachio Ehara ◽  
Essam Aboud
Keyword(s):  
Gravity Data ◽  
Data Interpretation ◽  
3D Gravity ◽  
2D And 3D

Gravity data inversion for Moho depth modeling in the Hellenic area

2015 ◽  
Vol 173 (4) ◽  
pp. 1223-1241 ◽  
Author(s):  
Vassilios N. Grigoriadis ◽  
Ilias N. Tziavos ◽  
Grigorios N. Tsokas ◽  
Alexandros Stampolidis
Keyword(s):  
Gravity Data ◽  
Moho Depth ◽  
Data Inversion

scholarly journals Nonlinear 3-D inversion of gravity data over a sulfide ore body

2000 ◽  
Vol 39 (2) ◽  
pp. 179-188
Author(s):  
J. García Abdeslem
Keyword(s):  
Gravity Data ◽  
Ore Body ◽  
Sulfide Ore

El gradiente gravimétrico horizontal y el principio de superposición de campos potenciales son utilizados en la interpretación de los datos gravimétricos de un yacimiento de sulfuros mediante una estructura 3-D de densidades. El yacimiento está constituido por sulfuros masivos y diseminados, principalmente de esfalerita, alojados en caliza. El gradiente horizontal de la anomalía gravimétrica permitió inferir en forma aproximada la extensión lateral del yacimiento. La interpretación de los datos gravimétricos se propone como un problema inverso que se realiza en forma iterativa, siguiendo un criterio de mínimos cuadrados con amortiguamiento. El modelado inverso está acotado con valores de densidades y espesor del yacimiento, obtenidos a partir de un pozo perforado sobre la zona mineralizada.

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