Direction of resolved shear stress: a construction and discussion

A simple construction facilitates identification of the direction of resolved shear stress for Andersonian conditions (in which one principal axis is vertical). A constructed horizontal ‘rake guide’, for specific stress and strike, will project perpendicularly onto any dipping plane as the direction of resolved shear stress. Consideration of rake guides, for different strikes for each fixed stress state, illustrates that tectonic regimes are identifiable by ranges, but not by individual values of rake. The ‘tectonic regime parameter’ and the ‘rake guide angle’ are useful parameters for Andersonian stress.