Computer modelling and visualisation of the structural deformation caused by movement along geological faults

Abstract

The computer modelling and visualisation of deformation caused by movement along faults has enhanced our understanding of the evolution of fault-related structures in the geological record. In particular, the development of computer software to carry out structural restoration and section balancing has provided earth scientists with an effective tool for validating structural interpretations constructed from geological and geophysical data. This paper describes both two- and three-dimensional geometric methods for modelling hanging wall deformation in response to fault movement. Equations are presented for the definition of two-dimensional fault geometries and for the determination of hanging wall geometry following movement over these faults. The Chevron and inclined shear constructions and fault-bend fold theory are described in a format to enable easy conversion into computer algorithms. The modelling of fault movement in three-dimensions is also considered in the context of the Chevron construction. Schematic models are presented which show hanging wall deformation caused by extensional, compressional and, most importantly, strike-slip movement over a complex fault surface. In addition, a new geometric technique for the restoration of deformed hanging wall surfaces is described. This technique has been called flexural flattening and involves flattening a surface represented as a mesh of triangles, back to horizontal. It has the advantages of maintaining the area of the surface before and after restoration and is relatively simple to apply in comparison to three-dimensional implementations of existing geometric methods.