epicenter vs epicentre

epicenter

epicentre

verb
  • Of an earthquake: to have its epicentre (at a specified location). 

noun
  • The point on the surface of the earth directly above an underground explosion. 

  • The geographical area in which an ongoing disaster, illness, crisis, or other destructive event is currently most severe. 

  • The point on the land or water surface directly above the focus, or hypocentre, of an earthquake. 

  • The focal point of any activity, especially if dangerous or destructive. 

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