Thrust and reverse faults

A thrust fault is caused by in-situ stress conditions in which

$$\left\lbrace \begin{array}{l} S_1 = S_{Hmax} \\ S_2 = S_{hmin} \\ S_3 = S_v \\ \end{array}\right.$$ (5.4)

These stress conditions are typical of locations with high compressive tectonic strains. For example, sedimentary basins close to the Andes and Himalayas foothills are under reverse faulting regime. The fault plane is a shear rupture plane. Its orientation is $(\pi/4 + \varphi/2)$ in vertical direction from a vertical plane perpendicular to $S_{Hmax}$. The blocks move along the direction of $S_{Hmax}$ and do work against gravity $S_v$ (surface lift). As with normal faulting, the block above the fault is called the “hanging-wall” and the block below the “footwall”.

Figure 5.13: Thrust fault example.

A fault that may have been caused by paleo-stresses corresponding to a normal stress regime, but now moves according to in-situ stress conditions of a thrust fault stress environment is termed a reverse fault.

Figure 5.14: Reverse fault example.