Next Generation Three-Dimensional Geologic Modeling and Inversion

Earth and Planetary Science Letters

Aillères

Grose

et al. 2016

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International audienceThree-dimensional structural modeling is gaining importance for a broad range of quantitative geoscientific applications. However, existing approaches are still limited by the type of structural data they are able to use and by their lack of structural meaning. Most techniques heavily rely on spatial data for modeling folded layers, but are unable to completely use cleavage and lineation information for constraining the shape of modeled folds. This lack of structural control is generally compensated by expert knowledge introduced in the form of additional interpretive data such as cross-sections and maps. With this approach, folds are explicitly designed by the user instead of being derived from data. This makes the resulting structures subjective and deterministic. This paper introduces a numerical framework for modeling folds and associated foliations from typical field data. In this framework, a parametric description of fold geometry is incorporated into the interpolation algorithm. This way the folded geometry is implicitly derived from observed data, while being controlled through structural parameters such as fold wavelength, amplitude and tightness. A fold coordinate system is used to support the numerical description of fold geometry and to modify the behavior of classical structural interpolators. This fold frame is constructed from fold-related structural elements such as axial foliations, intersection lineations, and vergence. Poly-deformed terranes are progressively modeled by successively modeling each folding event going backward through time. The proposed framework introduces a new modeling paradigm, which enables the building of three-dimensional geological models of complex poly-deformed terranes. It follows a process based on the structural geologist approach and is able to produce geomodels that honor both structural data and geological knowledge

Section: Discussion and Perspectivesmentioning

confidence: 99%

“…The shape of the fold hinge is another important characteristic for describing the geometry of a fold [Jessell et al, 2014]. It is represented by the fold hinge shape parameter p (Fig.…”

Section: Simplified Fold Interpolator For Similar Foldsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Implicit modeling of folds and overprinting deformation

Earth and Planetary Science Letters

Aillères

Grose

et al. 2016

Self Cite

“…Geological models, and as a result, geological inversions are usually under constrained. However, there are often geological rules and additional geological knowledge that are not directly incorporated into the interpolation schemes that would further constrain subsurface geometries [Jessell et al, 2010a[Jessell et al, , 2014.…”

Section: Introductionmentioning

confidence: 99%

Inversion of geological knowledge for fold geometry

Grose

Aillères

Journal of Structural Geology

et al. 2019

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The process of building three-dimensional (3D) geological models can be framed as an inverse problem where a model describing the 3D distribution of rock units is non-uniquely derived from geological observations. The inverse problem theory provides a powerful framework for inferring these parameters from all geological observations, in a similar way to how a geologist can iteratively update their structural interpretation while mapping. Existing geological knowledge is usually indirectly incorporated into 3D models using the geologist's non-unique interpretation as form lines, cross sections and level maps. These approaches treat constraints derived from geological knowledge in the same way as direct observations, diluting and confusing both information provided by geological knowledge and hard data resulting in significant subjectivity. We present a geological inversion using Bayesian inference where geological knowledge can be incorporated directly into the interpolation scheme with likelihood functions and informative prior distributions. We demonstrate these approaches on a series of synthetic fold shapes as a proof of concept and a case study from the Proterozoic Davenport Province in the Northern Territory, Australia. The combined inversion of geological data and knowledge significantly reduces the uncertainty in possible fold geometries where data is sparse or highly ambiguous. This could be used by geologists while mapping to propagate information about uncertainties throughout the mapping/model building process and would allow for different structural interpretations to be rapidly tested for targeted data collection.

“…The representation of geological interfaces as equipotential surfaces of one or several scalar fields, often termed implicit modeling, has become a powerful approach to build geological models [Lajaunie et al, 1997;Cowan et al, 2003;Chilès et al, 2004;Frank et al, 2007;Calcagno et al, 2008;Hjelle et al, 2013;Caumon et al, 2013;Hillier et al, 2014;Jessell et al, 2014]. This approach is particularly interesting when representing continuous stratigraphic sequence, because it allows for the representation of a conformable continuum of surfaces at once [Jessell et al, 2014]. It can also be useful to represent structural elements, such as foliations and axial surface fields [Lajaunie et al, 1997;Maxelon et al, 2009;Massiot and Caumon, 2010;Laurent et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

Iterative Thickness Regularization of Stratigraphic Layers in Discrete Implicit Modeling

2016

Math Geosci

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International audienceDiscrete implicit modeling consists in representing structural surfaces as isovalues of three-dimensional piecewise linear scalar fields, which are interpolated from available data points. Data are expressed as local constraints that can enforce the value of the scalar fields as well as their gradients. This paper illustrates some limitations of published discrete implicit methods, related to the difficulty of controlling the norm of scalar field gradient and its evolution over the interpolated domain. It is shown that important artifacts may arise due to the intrinsic dependence between variations in the norm and the direction of the scalar field gradient, from one element to its neighbors. Evidence that these artifacts are related to mesh facet direction with respect to gradient direction are given. The artifacts lead to rapid and uncontrolled variations of thickness that may induce erroneous interpolations. This paper proposes two original approaches to overcome these problems. The first one consists in iteratively adjustingthe norm of scalar field gradients in the direction obtained after previous iterations. The second solution consists in optimizing the mesh used by the interpolation. This requires finding appropriate mesh facet orientationwith respect to scalar field gradient. These methods demonstrate that the results of discrete implicit surface interpolation can be improved and call for further development of available interpolation schemes