The patterns of multiple thrust or reverse faults are significantly different than those of other fault types. Though rare, conjugate thrust fault sets do exist as shown in Figure 1.

Figure 1. Conjugate thrust faults in an argillaceous rock, Pennsylvania. From Nickelson and Cotter (1983). The two inclined fracture systems are locally filled by pods of calcite. Although the authors reported the presence of a small amount of slip along the faults, here the arrows indicating the sense of motion along the faults are inferred based on the geometry of the tail veins and the orientation of the cleavages within the fracture zones (inset). Note that the cleavage traces bisect the larger of the fault intersection angles, which is consistent with the reduction spots (the ellipse on the x-y plane). The curved lines (SSS) are traces of slip surfaces interpreted to be pre-consolidation structures.

There are several reasons for these differences as discussed under 'Mechanisms and Mechanics of Multiple Thrust Fault Sets.' Thrust faults form in response to a stress regime in which the maximum compressive stress is horizontal and the minimum principal stress is vertical (see, for example, Figure 1b under 'Multiple Fault Sets'). This, together with the vertical anisotropy in the mechanical properties of layered rocks in Earth's crust, induce other instabilities in the resulting deformation, namely buckling and bending either before thrust faulting or during, and sometimes even after the faulting. As a result most thrust faults are associated with folds to some degree (Figure 2 and Figure 3).

Figure 2. Conjugate thrust faults in the sandstones (light) and shales (dark) of the Entrada Formation exposed on the symmetric cuts of HWY 276 near Mt. Ellsworth, SE Utah. From Aydin 1973.

Figure 3. Thrust faults and folds on a seismic section across the Tip-Top field, WY. Notice the similarity between the fold and fault structures here and that in Figure 2 suggesting a similar pattern of anisotropy and the distribution of weak horizons in different scales. From Groshong (2006, 2nd ed.).

The other factor with considerable influence on the thrust fault patterns is the free surface or interfaces or weak gliding horizons on which thrust sheets with large transport are localized (Figure 4). The resulting geometry is such that the faults may be considered as flats along the weak surfaces or units and steep segments which represent the portion of the fault crossing the stiff unit's up section. Due to the limited strength of thin rock slabs or sheets, imbrications in the thrust fault patterns and stacking up the sheets are common. In this regard, one of the most common thrust fault patterns is the so-called thrust duplex which includes slabs or sheets bounded along the bottom and the top by sub-parallel thrust faults. Figure 4 also illustrates a tectonic deformation style predominantly confined within the sedimentary cover over a rather stable basement. This style without the involvement of the basement as far as large scale faulting is concerned, is called thin-skinned tectonics.

Figure 4. A section of the Summit Field in the Appalachians of West Virginia and Pennsylvania showing thrust faults most likely initiated along shale (sh) and salt beds and then cut upsection and ending with fault propagation folds. From Gwinn (1964).

On the other hand, Figure 5 is an example of basement involved thrusting or thick-skinned tectonics which is one of the characteristics of the Rocky Mountain region of the USA.

Figure 5. A cross section across the southern Appalachian Valley-and-Ridge in Tennessee showing a series of west verging thrust faults with flat and relatively steep segments. Data from Roedder et al. (1978); modified by Suppe (1985).

In contrast to most multiple normal fault sets, there is a strong asymmetry in the large-scale thrust fault sets; the set verging to the transport direction dominates the pattern although what are commonly referred to as back thrusts, which have a vergence in the direction opposite to the overall transport direction, also occur.