P waves are most easily described as a slip deformation in relation to material science. The motion of propagation is in the horizontal direction causing compressions of the medium around the particle and dislocations of the medium in front of and behind. Figure 3.1 more clearly represents the description of the compression and expansion of the dislocations in the particle medium. These dislocations move the quickest and are the first to be recorded by seismographs.
S waves create waves through the solid medium of the Earth that would look similar to waves that form across the surface of the ocean. S wave dislocations create vertical waves that propagate in the horizontal direction. Figure 3.2 represents the wavelike nature created by the s dislocations which shears the medium as it passes through it. These waves are the slowest of body waves and are measured secondary to P waves. The difference in time between the recordings of the P waves and the S waves help in determining the amplitude of the S wave and the magnitude of the earthquake itself.