Velocity field for the trishear model

A general method for the derivation of velocity fields consistent with the basic kinematics of the trishear model of fault-propagation folding is given. We show that the fields can be written as explicit functions of position within the deformation zone. To demonstrate the approach, several different linear and non-linear velocity fields are derived and plotted. We show that the trishear zone need not be symmetric and that the trishear model produces 1/r singular strain rates, consistent with results for cracks in elastic–plastic materials. A continuous formulation of heterogeneous trishear is also presented.