4. Seismic

4.1 Basic principles of seismic methods

Seismic methods are based on the study of mechanical wave propagation in the ground. The speed of wave propagation depends on the elastic properties of the materials.

• Several types of wave propagate simultaneously; we distinguish between volume waves (which always exist) and surface waves, which exist and propagate only in the vicinity of interfaces separating two materials with different elastic properties.

  Volume waves are themselves of two kinds:

  • The first are compressional waves, or longitudinal waves, or P-waves, because they propagate fastest and are the first to be observed on a ground motion record; the corresponding...