The sudden sinking or gradual downward settling of the Earth's surface with little or no horizontal motion. The movement is not restricted in rate, magnitude, or area involved. Subsidence may be caused by natural geologic processes, such as solution (karst phenomena), thawing, compaction, slow crustal warping, or withdrawal of fluid lava from beneath a solid crust; or by man's activity, such as subsurface mining or the pumping of oil or groundwater.
(Neuendorf, K.K.E. and others, 2005)
Earthquakes can cause rapid subsidence due to land level changes.
DGGS online catalog of government agency publications relating to: Subsidence
Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS) 3354 College Road, Fairbanks, AK 99709