happen vs supervene

happen

verb
  • To do or occur by chance or unexpectedly. 

  • To encounter by chance. 

  • To occur or take place. 

supervene

verb
  • To follow (something) closely, either as a consequence or in contrast. 

  • To be dependent on an earlier event. 

  • To be dependent on something else for existence, truth, or instantiation. 

  • To supersede. 

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