Plane Seismic Waves
This Demonstration shows the propagation of elastic waves, commonly known as seismic waves. Two types of seismic waves are shown here: pressure waves (P-waves) and shear waves (S-waves). The P-wave is longitudinal, and so oscillates along the direction of the wave propagation, while the S-wave shakes perpendicular to the travel direction.[more]
By combining these two types, you can simulate other types, such as Rayleigh waves. In such cases, the particles move in a circle or ellipse. The movement can be observed in detail by increasing the length of the trail.[less]
In the event of a real earthquake, the P-wave always precedes the S-wave, because the speed of P-waves is
while the speed of an S-wave is
where is the bulk modulus, μ is the shear modulus, and ρ is the density.