What forms the lower half of a fault?

The lower half of a fault is typically referred to as the "footwall." This is the block of rock that lies beneath the fault plane and remains stationary during fault movement. In contrast, the upper half is known as the "hanging wall," which moves downward in relation to the footwall during certain types of faulting, such as normal faults. The interaction between these two blocks is crucial in understanding geological processes and earthquake mechanics.