Our review illustrates how similar types of structural settings have been modeled using various designs. Comparison between these experimental set-ups reveals the strengths and limits of each design (Table 1) and illustrates the progressive improvement in designing models whose geometric and rheological properties are analogous to those of the geological prototypes.

Table 1. Scaling parameters used for experiment J18, assuming a 200-m-thick source layer.

  Fungen et al. 1986 Le Calvez and Vendeville, 1996 Sims et al. 1999 Le Calvez and Veneville, 2002
The trace of the faults at the base of the brittle layer are not forced to follow a predetermined profiled (basal velocity discontinuity), outside / within the zone of transfer. No / No No / Yes No / No Yes / Yes
The base of the brittle layer is not forced to remain horizontal and rigid, outside / within the transfer zone. No / No No / Yes Yes / Yes Yes / Yes
Fault blocks are allowed to subside outside / within the transfer zone No / No No / Yes Yes / Yes Yes / Yes
The graben asymmetry is imposed by boundary conditions outside / within the transfer zone No / No No / Yes No / No Yes / Yes

In the above discussion, we have shown how the first set of models using a brittle layer resting directly above a basal sheet (Faugère et al., 1984; McClay and Ellis, 1987; Vendeville, 1991) controlled the location, orientation, and sense of asymmetry of faults in pull-apart basins or in the relay zones. The design by Sims et al. (1999) represents an improvement of this set-up by incorporating a basal viscous layer. This design, however still constrains too much fault location and orientation in the model. Although the third design by Le Calvez and Vendeville (1996) allowed to effectively insulate the brittle layer from the model base, it still does not permit significant fault-block vertical movements and rotations. The new set-up illustrated in this article represents only the latest step in the evolution of model design and will with no doubt be superceded by newer designs in the future. With this design, experimenters can confidently model the interaction of normal faults as they propagate along-strike during extension above a weaker viscous layer. The same design could easily be adapted to study fault interaction in different tectonic regimes, such as regional strike-slip or compressional deformation.