Editing Seismology (section)

===Surface waves===
Surface waves are the result of P and S waves interacting with the surface of the Earth. These waves are [[Dispersion (optics)|dispersive]], meaning that different frequencies have different velocities. The two main surface wave types are [[Rayleigh wave]]s, which have both compressional and shear motions, and [[Love wave]]s, which are purely shear. Rayleigh waves result from the interaction of P waves and vertically polarized S waves with the surface and can exist in any solid medium. Love waves are formed by horizontally polarized S waves interacting with the surface, and can only exist if there is a change in the elastic properties with depth in a solid medium, which is always the case in seismological applications. Surface waves travel more slowly than P waves and S waves because they are the result of these waves traveling along indirect paths to interact with Earth's surface. Because they travel along the surface of the Earth, their energy decays less rapidly than body waves (1/distance<sup>2</sup> vs. 1/distance<sup>3</sup>), and thus the shaking caused by surface waves is generally stronger than that of body waves, and the primary surface waves are often thus the largest signals on earthquake [[seismogram]]s. Surface waves are strongly excited when their source is close to the surface, as in a shallow earthquake or a near-surface explosion, and are much weaker for deep earthquake sources.<ref name=Gubbins1990/>