Final answer:
The fault where the hanging wall block moves up relative to the footwall with a pure dip slip motion is known as a reverse fault. A specific type of reverse fault with a gentle dip is called a thrust fault, which results in the allochthonous block being thrust over the autochthonous block.
Step-by-step explanation:
If the hanging wall block moves up relative to the footwall and the motion is pure dip slip, then the fault is a reverse fault.
In geology, the blocks on either side of a fault are referred to as the walls. When the hanging wall moves up compared to the footwall in a dip-slip motion, the structure formed is known as a reverse fault. This occurs because of compression and shortening of the Earth's crust. When the dip of a reverse fault is less than 30°, it is specifically classified as a thrust fault, and in these cases, the moving block is termed the allochthonous block, which is thrust over the autochthonous block. Features such as a klippe and windows can form as a result of erosion relating to these thrust faults.