Flow perturbations: a tool to study and characterize heterogeneous deformation

This paper introduces the use of the geometry of flow perturbations to improve our understanding of heterogeneous flow, and to allow classification of structures based on kinematics. A flow perturbation is the deviation of a heterogeneous flow pattern from the background homogeneous flow. Perturbation patterns can be visualised as open or closed loops of vectors, which occur in pairs, rows or groups of four. They usually cross-cut rheological interfaces, and can be subdivided into those that cross interfaces twice or four times. Most geological structures belong to the first group, while initiating buckle folds belong to the second group.