3D Structural and Mechanical Modelling of Fault Geometries

Faulting is accommodated by discontinuous deformation along the fault surface and continuous near field deformation in the wall rock. If the displacement along the fault decreases from a maximum (at the centre) towards the tip of the fault, markers in the wall rock are deflected either convex or concave into the direction of slip. This deflection is known as normal- and reverse fault drag, respectively. This project plans to extend the results of recent 2D mechanical models to 3D, comparing the results with 3D geometric models of faults in small scale rock samples. 3D structural models will be constructed from serial sections through rock samples containing faults with associated fault drag. Numerical modelling of fault drag using a boundary element code (Poly3D) will provide quantitative analysis of 3D fault drag around ideal elliptical fault surfaces. As a next step, integration of natural fault geometries with variable fault dip and displacement along the fault into the numerical models will result in more realistic effects, which show more complex and probably interacting drag geometries. Analysing natural and modelled geometries, the boundary conditions for the development of non-cylindrical and/or non-symmetrical drag effects will be determined. This study will evaluate the applicability of plane strain (2D) models to the 3D geometries of fault drag, which might in many cases be an inappropriate simplification. The results may find practical application in locating and understanding of hydrocarbon traps along non-cylindrical fault drag structures.