Wave

Wave:
A periodic vibrational disturbance in which energy is propagated through or on the surface of a medium without translation of the material. Waves can be differentiated by their frequency, amplitude, wavelength and speed of propagation.

Body wave:
A wave that propagates through a medium rather than along an interface. P-waves and S-waves are examples of body waves.

1. P-wave: An elastic body wave or sound wave in which particles oscillate in the direction the wave propagates. P-waves are the waves studied in conventional seismic data. P-waves incident on an interface at other than normal incidence can produce reflected and transmitted S-waves, in that case known as converted waves. (Synonyms: acoustic wave, compressional wave, dilatational wave)
2. S-wave: An elastic body wave in which particles oscillate perpendicular to the direction in which the wave propagates. S-waves are generated by most land seismic sources, but not by air guns. P-waves that impinge on an interface at non-normal incidence can produce S-waves, which in that case are known as converted waves. S-waves can likewise be converted to P-waves. S-waves, or shear waves, travel more slowly than P-waves and cannot travel through fluids because fluids do not support shear. Recording of S-waves requires receivers coupled to the solid Earth. Interpretation of S-waves can allow determination of rock properties such as fracture density and orientation, Poisson's ratio and rock type by crossplotting P-wave and S-wave velocities, and by other techniques. (Synonyms: shear wave, tangential wave)
3. SH-wave: A shear wave that is polarized so that its particle motion and direction of propagation are contained in a horizontal plane.
4. SV-wave: A shear wave that is polarized so that its particle motion and direction of propagation occur in a vertical plane.
5. Converted wave: A seismic wave that changes from a P-wave to an S-wave, or vice versa, when it encounters an interface.

Surface wave:
A wave that propagates at the interface between two media as opposed to through a medium. A surface wave can travel at the interface between the Earth and air, or the Earth and water. Love waves and Rayleigh waves are surface waves.

1. Love wave: A type of surface wave in which particles oscillate horizontally and perpendicularly to the direction of wave propagation.
2. Rayleigh wave: A type of surface wave in which particles move in an elliptical path within the vertical plane containing the direction of wave propagation. At the top of the elliptical path, particles travel opposite to the direction of propagation, and at the bottom of the path they travel in the direction of propagation. Because Rayleigh waves are dispersive, with different wavelengths traveling at different velocities, they are useful in evaluation of velocity variation with depth. Rayleigh waves make up most of the energy recorded as ground roll.
   
3. Stoneley wave: A type of large-amplitude interface, or surface, wave generated by a sonic tool in a borehole. Stoneley waves can propagate along a solid-fluid interface, such as along the walls of a fluid-filled borehole and are the main low-frequency component of signal generated by sonic sources in boreholes. Analysis of Stoneley waves can allow estimation of the locations of fractures and permeability of the formation. Stoneley waves are a major source of noise in vertical seismic profiles.
4. Tube wave: (1) A Stoneley wave that occurs at the low frequencies of seismic data. (2) An interface wave that occurs in cased wellbores when a Rayleigh wave encounters a wellbore and perturbs the fluid in the wellbore. The tube wave travels down the wellbore along the interface between the fluid in the wellbore and the wall of the wellbore. A tube wave suffers little energy loss and typically retains a very high amplitude which interferes with reflected arrivals occurring later in time on vertical seismic profile (VSP) data. Because the tube wave is coupled to the formation through which it is traveling, it can perturb the formation across open fractures intersecting the borehole. This squeezing effect can generate secondary tube waves which travel both up and down from the fracture location. Such events can be diagnostic of the presence of open fractures and their amplitude related qualitatively to the length and width, e.g., volume of the fluid-filled fracture space. This effect is generally seen only in shallow formations where the overburden pressure is lower.
5. Dispersion: A type of distortion of a wave train in which the velocity of the wave varies with frequency. Surface waves and electromagnetic body waves typically exhibit dispersion, whereas P-waves in most rocks show little change in velocity with frequency.
6. Ground roll: A type of coherent noise generated by a surface wave, typically a low-velocity, low-frequency, high-amplitude Rayleigh wave. Ground roll can obscure signal and degrade overall data quality, but can be alleviated through careful selection of source and geophone arrays, filters and stacking parameters.