Non-plane strain in section balancing: calculation of restoration parameters

We derive a set of equations which can be used to calculate the finite strain ellipsoid and longitudinal strains from measured strain axial ratios and orientations. The argument is based upon strain data from sections which carry the most relevant structural and kinematic data—the cross-section plane and the cleavage plane. These equations can be used to calculate pinline trajectories for correct restoration of sheared units in balanced sections.