Part 4/6:
There was a distinction made between the types of seismic waves generated by building collapses versus those produced by natural seismic events. Typically, a standard building demolition would result in both primary (P) waves and secondary (S) waves. However, the seismic readings indicated that only surface waves were present following the collapses of the World Trade Center buildings, which does not align with the typical signature of a controlled demolition.