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S-wave

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	Topics S-wave Topic Home A type of seismic waveSeismic wave A seismic wave is a wave that travels through the Earth, most often as the result of a tectonic earthquake, sometimes from a... , the S-wave, secondary wave, or shear wave, sometimes called an elastic S-wave, is one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waveSurface wave In physics, a surface wave can refer to a mechanical wave that propagates along the interface between differing media, usual... s. The S-wave moves as a shear or transverse waveTransverse wave A transverse wave is a wave that causes a disturbance in the medium perpendicular to the direction it advances.... , so motion is perpendicular to the direction of wave propagation: S-waves, like waves in a rope, as opposed to waves moving through a slinky, the P-waveP-wave A P-wave, sometimes called an elastic P-wave, or primary wave is a kind of seismic waves, one of the two types o... . The wave moves through elastic media, and the main restoring force comes from shear effects. These waves are divergenceless and obey the continuity equation for incompressible media. Its name, S for secondary, comes from the fact that it is the second direct arrival on an earthquake seismogramSeismogram A seismogram is a graph output by a seismograph.... , after the compressional primary wave, or P-wave. Unlike the P-wave, the S-wave cannot travel through the molten outer core of the Earth, and this causes a shadow zoneShadow Zone For other uses of the word Shadow zone see the Disambiguation page... for S-waves opposite to where they originate. They can still appear in the solid inner coreInner core The Earth has several distinct layers, the deepest of which is the core.... : when a P-wave strikes the boundary of molten and solid cores, called the Lehmann discontinuityLehmann discontinuity The Lehmann discontinuity, named after seismologist Inge Lehmann, is the discontinuity in seismic velocity near a depth of 2... , S-waves will then propagate in the solid medium. And when the S-waves hit the boundary again they will in turn create P-waves. In fact, this property allows seismologistsSeismology Seismology is the scientific study of earthquakes and the movement of waves through the Earth.... to determine the nature of the inner core. The velocity of an S-wave in an isotropic medium can be described by the shear modulusShear modulus Overview In materials science, shear modulus, G, or sometimes S, sometimes referred to as the modulus of rigidity, is d... and densityDensity Density is a measure of mass per unit of volume.... . As transverse waves, S-waves exhibit properties, such as polarizationPolarization In electrodynamics, polarization is the property of electromagnetic waves, such as light, that describes the direction of t... and birefringenceBirefringence Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certa... , much like other transverse waves. S-waves polarized in the horizontal plane are classified as SH-waves. If polarized in the vertical plane, they are classified as SV-waves. When an S- or P-wave strikes an interface at an angle other than 90 degrees, a phenomenon known as mode conversion occurs. As described above, if the interface is between a solid and liquid, S becomes P or vice versa. However, even if the interface is between two solid media, mode conversion results. If a P-wave strikes an interface, four propagation modes may result: reflected and transmitted P and reflected and transmitted SV. Similarly, if an SV-wave strikes an interface, the same four modes occur in different proportions. The exact amplitudes of all these waves are described by the Zoeppritz equationsZoeppritz equations In seismology, the Zoeppritz equations describe how seismic waves are transmitted and reflected at media boundaries.... , which in turn are solutions to the wave equationWave equation The wave equation is an important partial differential equation that describes the propagation of a variety of waves, such a... . See also Love waveLove wave In seismology, Love waves are surface seismic waves that cause horizontal shifting of the earth during an earthquake.... P-waveP-wave A P-wave, sometimes called an elastic P-wave, or primary wave is a kind of seismic waves, one of the two types o... Rayleigh waveRayleigh wave Summary Rayleigh waves, also known as the Rayleigh-Lamb Wave or "ground roll", are a type of surface wave associated on the Ea... Transverse waveTransverse wave A transverse wave is a wave that causes a disturbance in the medium perpendicular to the direction it advances.... Further reading