--> Understanding Geomechanical Deformation by Coupling Distinct Element Forward Modeling and Structural Restoration: Insight From Compressional and Extensional Numerical Models
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AAPG ACE 2018

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Understanding Geomechanical Deformation by Coupling Distinct Element Forward Modeling and Structural Restoration: Insight From Compressional and Extensional Numerical Previous HitModelsNext Hit

Abstract

Forward modeling and structural restoration are complementary tools used to analyze deformation through time. Forward simulations based on the distinct element method (DEM) are capable of producing complex and realistic structures, but like all physics-based forward Previous HitmodelsNext Hit it generally proves difficult to reproduce the precise geometry of a specific natural structure. In contrast, structural restoration provides valuable insight into the displacement field of natural geologic structures. However, these methods simplify the real mechanics, often impose a style of deformation through boundary conditions, and generally lacks rigorous validation as the reference paleo-geometry is unknown. We combine these two methods by performing 3D structural restorations of DEM forward Previous HitmodelsNext Hit. This serves both to evaluate the 3D restoration methods, and provides insights into the mechanics of fault-related folds.

We use a 3D distinct element code to model two tectonic regimes: one compressional and one extensional. In both contexts, the studied model is a box filled with balls bonded by breakable contacts. The bottom of the model represents a detachment containing two different frictional zones separated by an en-echelon boundary. This friction transition defines an area of fault nucleation, and, by its non-linear shape, enables the formation of non-cylindrical structures. In addition, there is mechanical layering to facilitate flexural slip. For the compressional system, a vertical box wall has an imposed Previous HithorizontalNext Hit velocity. The deformation of the extensional system is initiated by a tilt of the box. In both cases, Previous HitlayersNext Hit of particles are deposited to mimic syntectonic sedimentation. We show that the DEM enables us to model realistic, non-cylindrical, 3D geological structures, e.g. fault-related folds and growth geometries, and helps to understand natural deformation processes.

We use two methods of 3D structural restoration to recover the states of the deformed distinct element Previous HitmodelsNext Hit. One technique is based on continuum mechanics and displacement boundary conditions. The other is purely geometric and based on the paleo-chronostratigraphic coordinates. As the displacement of each ball is known through time, forward Previous HitmodelsNext Hit provide an excellent benchmark to test the restoration validity. We evaluate the extent to which each restoration method is able to recover the earlier states of the distinct element Previous HitmodelsTop, and discuss implications for restoration of natural cases.