subsidence

noun

the motion of a surface (usually, the Earth's surface) as it shifts downward relative to a datum such as sea-level

Pronunciation: /ˈsʌbsɪdəns/ / /ˈsʌbsədəns/ / /sʌbˈsaɪdəns/

Etymology: Latin subsidens, subsidentis, present participle of subsidere. Equivalent to subside + -ence.

The process of becoming less active or severe.
“The subdual or subsidence of the more violent passions.”
A sinking of something to a lower level, especially of part of the surface of the Earth due to underground excavation, seismic activity or underground or ground water depletion, or the rocks in a geological basin, due to continued deposition from above.
“In the early hours of April 28, 1953, it was completely blocked by a subsidence, which caused the death of five persons, when a pair of semi-detached houses collapsed into the cavity.”
“Everyone knows that a main line running through a coalfield is prone to speed restrictions because of land subsidence. […] The rate of subsidence may vary from less than an inch a month in the case of a deep seam of coal, to as rapid a decline as 16in a month above a shallow seam. The effect of subsidence on permanent way and civil engineering structures needs no emphasis.”