B.Unlike the oscillations of particles due to heat, elastic waves propagate in a very organized way. 1.Body waves propagate outward from a source along three-dimensional surfaces called wavefronts, similar to the rings of waves seen propagating outward in a pond centered where a pebble has splashed. The perpendiculars to wavefronts are called rays. Body wave propagation, including reflection and refraction is often summarized by drawing ray paths. Ray paths follow a principle of least time, from which Snell's Law can be proved.
Surface waves are elastic waves whose energy is confined close to the surface of the earth.
The energy of a surface wave exponenentially decays with depth. Rayleigh waves are slower than Love waves about 0.9 times the S wave velocity at the surface. The particle motion in Rayleigh waves lies in the plane containing the source, seismometer and center of the earth. The particle motion of Love waves is perpendicular to this plane. The velocities of different frequency components are a function of the elastic and density sturcture of the upper surface of the Earth.