substratal vs tectonic

substratal

adj
  • Of or pertaining to a substratum. 

  • Specifically, pertaining to a substrate language. 

tectonic

adj
  • Of or relating to construction or to architecture 

  • Structural 

  • Of, relating to, or caused by large-scale movements of the Earth's (or a similar planet's) lithosphere 

  • momentous, utter, vast 

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