Ground surface subsidence is an old problem. It has existed but went unnoticed until recent years due to the population growth and the rising living standards, as discussed in Section 1.2, as more marginal land is being developed. Subsidence covers large areas subjected to underground mining, pumping of groundwater, oil, and natural gas, as well as floods, underground fire, tree roots, construction operations, and pollution intrusion. The term subsidence was first used in geology in 1853 by Charles Lyell. The American Geological Institute (Gary et al., 1972) describes subsidence as (1) a local mass movement that involves principally the gradual downward settling or sinking of the solid earth’s surface with little or no horizontal motion and does not occur along a free surface; and (2) a sinking of a large part of the earth’s crust due to tectonic movements.