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Resolution of a stress tensor onto differently oriented planes. For two compression-positive principal stresses, the resolved normal stress and shear stress trace a Mohr circle as the plane normal rotates, with double the physical rotation angle.

Reduction of distance between material markers during tectonic deformation. Folding, reverse faulting and distributed strain can accommodate it; the shortening direction alone does not determine all three principal stresses.

The Tresca yield criterion bounds the largest resolved shear stress, expressed through the principal stresses. In spherical symmetry, the two tangential principal stresses coincide, so $f=|{\tau }_{rr}-{\tau }_{\theta \theta }|/2$. Here ${\tau }_Y$ is a shear yield stress; the corresponding uniaxial yield strength is $2{\tau }_Y$.