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 give n. We show that the fields can be written as explicit functions of position within the deformation zone. To demonstrate the approach, several differen t linear and non-linear velocity fields are derived and plotted. We show th at the trishear zone need not be symmetric and that the trishear model prod uces 1/r singular strain rates, consistent with results for cracks in elast ic-plastic materials. A continuous formulation of heterogeneous trishear is also presented. (C) 2000 Elsevier Science Ltd. All rights reserved.