I think the term you may be looking for here is called a hanging wall. It is simply a block of rock above a fault. A crack in the crust is called a fault. A block of rock below a fault is called a foot wall. When an earthquake occurs, there is stress placed on the crust of the Earth. The link I am posting shows a good picture and diagram of a hanging wall which makes it much easier to understand. The hanging wall determines whether the fault is a normal fault or a reverse fault. It has to do with tension (hanging wall moves down) and compression (hanging wall moves up).