What occours when the hanging wall moves down relative to a footwall

The answer is normal fault. A normal fault occurs when the hanging wall falls below the footwall and where there are extension forces on the fault in the crust. These forces lengthen the faulted section of rock. This is unlike in reverse fault that shortens the faulted section of rock and forces the hanging wall to move up in relation to the footwall. An example of a normal fault is the Great Rift Valley in Africa.