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 150 meters of slip. Note how the foreland (leading) limb of the fold is even more overturned. The hinterland limb continues to lengthen. The strain in the immediate hanging wall and footwall of the ramp iincreases in difference. Click on the image to see what happens with 200 meters of slip on the decollement.