page_title: Rayleigh wave
section_title: Rayleigh waves from earthquakes
hierarchical_section_title: Rayleigh wave / Rayleigh waves in geophysics / Rayleigh waves from earthquakes
caption_attribution_description: English: Rayleigh wave direction
context_page_description: Rayleigh waves are a type of surface acoustic wave that travel along the surface of solids. They can be produced in materials in many ways, such as by a localized impact or by piezo-electric transduction, and are frequently used in non-destructive testing for detecting defects. Rayleigh waves are part of the seismic waves that are produced on the Earth by earthquakes. When guided in layers they are referred to as Lamb waves, Rayleigh–Lamb waves, or generalized Rayleigh waves.
context_section_description: Because Rayleigh waves are surface waves, the amplitude of such waves generated by an earthquake generally decreases exponentially with the depth of the hypocenter (focus).  However, large earthquakes may generate Rayleigh waves that travel around the Earth several times before dissipating.
  In seismology longitudinal and shear waves are known as P-waves and S-waves, respectively, and are termed body waves. Rayleigh waves are generated by the interaction of P- and S- waves at the surface of the earth, and travel with a velocity that is lower than the P-, S-, and Love wave velocities.  Rayleigh waves emanating outward from the epicenter of an earthquake travel along the surface of the earth at about 10 times the speed of sound in air (0.340 km/s), that is ~3 km/s.
  Due to their higher speed, the P- and S-waves generated by an earthquake arrive before the surface waves.  However, the particle motion of surface waves is larger than that of body waves, so the surface waves tend to cause more damage. In the case of Rayleigh waves, the motion is of a rolling nature, similar to an ocean surface wave.  The intensity of Rayleigh wave shaking at a particular location is dependent on several factors:
  The size of the earthquake.
  The distance to the earthquake.
  The depth of the earthquake.
  The geologic structure of the crust.
  The focal mechanism of the earthquake.
  The rupture directivity of the earthquake.
  Local geologic structure can serve to focus or defocus Rayleigh waves, leading to significant differences in shaking over short distances.
caption: Rayleigh wave direction
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