Dynamic reverse modelling of flanking structures: a source of quantitative kinematic information

Flanking structures around planar discontinuities in an otherwise homogeneous flow develop a characteristic geometry that is potentially a source of kinematic information about the background flow. Analytical methods were used to calculate the velocity around a thin weak inclusion (representing a fracture) in linear viscous material. This approach allows modelling of flanking structures to very large strains. The velocity field around a given flanking structure can be calculated for the complete range of potential background flow fields, provided that the orientation of the fabric attractor and the bulk shear sense are known. Structures can be undeformed according to these velocity fields and, by quantifying the misfit between the actual and initial geometry, the vorticity number of the flow field and the duration of deformation accurately determined. With these two parameters established, the background (bulk) deformation involved in the formation of a specific flanking structure can be calculated.