convulsion vs earthquake

convulsion

noun
  • Violent turmoil. 

  • An uncontrolled fit, as of laughter; a paroxysm. 

  • An intense, paroxysmal, involuntary muscular contraction. 

earthquake

noun
  • A shaking of the ground, caused by volcanic activity or movement around geologic faults. 

  • Such a quake specifically occurring on the planet Earth, as opposed to other celestial bodies. 

verb
  • To undergo an earthquake. 

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