We use the Eshelby solution modified for a viscous fluid to model the evolution of three-dimensional flanking structures in monoclinic shear zones. Shearing of an elliptical crack strongly elongated perpendicular to the flow direction produces a cylindrical flanking structure which is reproducible with 2D plane strain models. In contrast, a circular or even narrow, slit-shaped crack exhibits a reduced magnitude of the velocity jump across the crack and results in smaller offset and a narrower zone of deflection than predicted with 2D-models. Even more significant deviations are observed if the crack axes are oriented at an oblique angle to the principal flow directions, where the velocity jump is oblique to the resolved shear direction and is modified during progressive deformation. The resulting triclinic geometry represents a rare example of triclinic structures developing in monoclinic flow and may be used to estimate the flow kinematics of the shear zone.
Research highlights
► In this study, 3D flanking structures are modelled which develop around an elliptical crack sheared in a defined background flow. ► The structures are dependent on the aspect ratio of the crack, and can thus not be sufficiently modelled by a 2D approach. ► Cracks oriented oblique to the shearing or stretching direction of a shear zone produce triclinic structures, which form in monoclinic shear zones and may be used to determine kinematics and finite strain.
