Anderson's Theory of Faulting

Assuming that there is no shear stress at the Earth's surface (shear stress cannot occur in fluids), one of the principal stress components must be vertical and thus the other two must be horizontal.

σv = σ1 normal fault

σv = σ2 reverse fault

σv = σ3 strike-slip fault

Anderson's Theory of Faulting

Normal, Reverse, and Strike-Slip Faults