Rayleigh waves, also known as "ground roll", are the result of an incident P and SV plane waves interacting at the free surface and traveling parallel to that surface. Ralyleigh waves travel along the surface with a retrograde elliptical particle motion and changing to prograde with depth passing through a node where there is no motion at all. Rayleigh wave particle motion is only found in the vertical plane with no tangential motion.  This means that Rayleigh waves are most commonly found on the vertical component of seismograms.  By definition Rayleigh waves are surface waves, so sources nearer to the surface tend to excite stronger Rayleigh waves than sources deep within the earth (Lay and Wallace, 1995).  Like Love waves, a Ralyleigh wave’s amplitude decreases exponentially with depth. These waves have a two-dimensional cylindrical geometry spread pattern that decreases with radius r from the source proportional to 1/√r (Lay and Wallace, 1995). This means that Rayleigh waves are usually the largest amplitude waves on a broadband seismometer. Rayliegh waves are also dispersive waves, that is, longer periods sample deeper material and arrive before shorter periods and make them a valuable tool for determining the upper crustal structure of a region. Dispersion is covered in more detail on the Dispersion page.

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