These faults are named according to the type of stress that acts on the rock and by the nature of the movement of the rock blocks either side of the fault plane. Normal faults occur when tensional forces act in opposite directions and cause one slab of the rock to be displaced up and the other slab down (Figure 10l-9). Figure 10l-9: Animation of a normal fault. Reverse faults develop when compressional forces exist (Figure 10l-10). Compression causes one block to be pushed up and over the other block.