3D form line construction by structural field interpolation (SFI) of geologic strike and dip observations

Interpreting and modelling geometries of complex geologic structures from strike/dip measurements using manually-drafted structural form lines is labour intensive, irreproducible and inherently limited to two dimensions. Herein, the structural field interpolation (SFI) algorithm is presented that overcomes these limitations by constructing 3D structural form lines from the vector components of strike/dip measurements. The SFI interpolation algorithm employs an anisotropic inverse distance weighting scheme derived from eigen analysis of the poles to strike/dip measurements within a neighbourhood of user defined dimension and shape (ellipsoidal to spherical) and honours younging directions, when available. The eigen analysis also provides local estimates of the plunge vector and associated Woodcock distribution properties to assure plunge-normal structural form line reconstruction with unidirectional propagation of form lines across fold and fan structures. The method is advantageous for modelling geometries of geologic structures from a wide range of structurally anisotropic data. Modelled vector fields from three case studies are presented that reproduce the expected bedding-foliation geometry and provide reasonable representation of complex folds from local to regional scales. Results illustrate the potential for using vector fields to support geologic interpretation through the direct visualization of geometric trends of structural features in 3D.