Polar Mohr constructions for strain analysis in general shear zones

The polar Mohr diagram is a useful tool for strain analysis in general shear zones. Polar Mohr diagrams for general shear zones can be constructed with the following measured data: (a) the stretches of two line markers which were originally perpendicular to each other; (b) the ratio of their stretches and the principal directions; (c) the stretches in the shear direction and in the principal direction; and (d) the stretches in any two directions. With these diagrams, the angle between eigenvectors, v, can be obtained, and the kinematic vorticity number Wk in the shear zone and the ratio of pure shear rate ε to simple shear rate γ during deformation can be computed with the formulae Wk = cos v and Wk = cos[cot(2ε/γ)].