Translations:Introduction - Chapter 1/10/en

Two basic types of waves are longitudinal waves and transverse waves. Longitudinal waves also are referred to as compressional waves or primary (P) waves. Transverse waves also are referred to as shear waves or secondary (S) waves. In a longitudinal wave, the oscillating particles of the medium are displaced parallel to the direction of propagation (i.e., the direction of energy transmission) of the wave. In a transverse wave, the particles are displaced in a direction perpendicular to the propagation direction. Seismic waves fall under two broad categories: (1) body waves, which travel through the body of the medium, and (2) surface waves, which travel near the surface.