low tide vs subsidence

low tide

noun
  • The time of day when the sea has receded to its lowest level. 

  • The tide at its lowest level for a particular tidal cycle at a certain place. 

subsidence

noun
  • 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. 

  • The process of becoming less active or severe. 

How often have the words low tide and subsidence occurred in a corpus of books? (source: Google Ngram Viewer )