If p-waves and S-waves can be traced back to faulting of rock in Earth's crust, then the origin of P-waves and S-waves can be traced back to what?

Answer choices:
- Something with a head, thorax, and abdomen
 - chemical messengers
 - flow of electrons
 - Electrical energy
 - Faulting of rocks in the crust
 - solid, liquid, gas
 - electromagnetic energy
 - that material's properties

 

     Faulting of rocks in the crust     