This benchmark attempts to reproduce the results of Buiter et al. 2016:
  Benchmarking numerical models of brittle thrust wedges,
  Journal of Structural Geology, 92, 140-177, 
  http://dx.doi.org/10.1016/j.jsg.2016.03.003.

More specifically, the provided input files aim to reproduce the numerical 
simulations of stable wedge experiment 1 illustrated in Figure 4-6 and unstable 
wedge experiment 2 illustrated in Figure 8-11 (Buiter et al., 2016). The setups 
of these experiments are shown in Figure 3a-b.

Experiment 1 tests whether model wedges in the stable domain of critical wedge 
theory remain stable when translated horizontally. A quartz sand wedge with a 
horizontal base and a surface slope of 20 degrees is pushed horizontally by 
inward movement of a mobile wall at the right boundary with a velocity of 2.5 
cm/hour. 

The basal angle is zero (horizontal), a thin layer separates the sand and boundary 
to ensure minimum coupling between the wedge and bounding box during translation,
and a sticky air layer is used above the wedge. Further, the purely plastic
material should not undergo any deformation during translation.

Experiment 2 tests how an unstable subcritical wedge deforms to reach the 
critical taper solution. This experiment builds a thrust wedge through a 
combination of mainly in-sequence forward and backward thrusting. In this 
experiment, horizontal layers of sand suffer 10 cm shortening by inward 
movement of a mobile wall with a velocity of 2.5 cm/hour. Deformation starts by 
forming a pop-up structure near the mobile wall. 

In the paper, it shows that the strain (Figure 10a-b) and strain-rate (Figure 
11) fields highlight several incipient shear zones that do not always accumulate 
enough offset to become visible in the material field (Figure 8-9). The pressure 
field of the models remains more or less lithostatic, with lower pressure values 
in (incipient) shear zones (Figure 10c-d).

Input files are provided for verifying that the models of brittle thrust wedge 
in this benchmark follows other numerical results and the analytical wedge 
theory in the paper. 

The resolution in exp2_low_resolution.prm and exp2_high_resolution.prm is 
2 mm/cell and 0.5 mm/cell, respectively. More details about the model setup 
are described in input files. 
