This diagram was created using the software program Trishear 4.5 by Richard Allmendinger (1997-2000), to whom we are grateful for making this and other software so widely and easily accessible to the geocommunity. The algorithm used in the software is described in the following two references:

- Allmendinger, R. W., 1998, Inverse and Forward numerical modeling of trishear fault-propagation folds. Tectonics, v. 17, 640-656.
- Zehnder, A. T. & Allmendinger, R. W., 2000, Velocity field for the trishear model: Journal of Structural Geology, v. 22, p. 1009-1014.

Here is the geometry after 200 meters of slip. The fold continues to grow. Note how drastically different the deformation/strain is at different levels. In one way it reverses a common conviction and/or assumption - the structure is more 'brittle' at depth and more 'ductile' at higher levels! Click on the image to see what happens with 250 meters of slip on the decollement.