1.Introduction Land subsidence can be defined as the differential sinking of the ground surface with respect to surrounding terrain or sea level.Land subsidence can result from natural causes such as tectonic motion and sea level rise or man-induced causes such as the withdrawal of groundwater,oil and gas,the extraction of coal and ores and the underground excavation for tunnel and cavern.Land subsidence is usually observed as a series of disastrous phenomena.  Land subsidence can be defined as the differential sinking of the ground surface with respect to surrounding terrain or sea level. Land subsidence can result from natural causes such as tectonic motion and sea level rise or man-induced causes such as the withdrawal of groundwater, oil and gas, the extraction of coal and ores and the underground excavation for tunnel and cavern. Land subsidence is usually observed as a series of disastrous phenomena. 1. Introduction