S-wave
From Biocrawler, the free encyclopedia.
A type of seismic wave, the S-wave moves in a shear motion perpendicular to the direction the wave travels. Think of the way a wave moves across a rope to imagine the S-wave versus a wave moving across a slinky, the P-wave. The wave moves through elastic mediums and the main restoring force comes from shear affects. These waves are divergenceless as shown in the equation of their gradient.
Its name comes from how it moves along the surface, due to shear forces and will arrive second to the faster P-wave. Unlike the P-wave, the S-wave cannot travel through the molten outer core of the Earth. This causes a shadow zone for S-waves opposite to where they originate.
The velocity of an S-wave can be described by the shear modulus and density.
Even though S-waves cannot pass through the molten outer core, they can still appear in the solid inner core. When a P-wave strike this boundry of molten and solid cores, called the Bullen Discontinuity, S-waves will propagate in the solid medium. And as the S-waves in turn move through the strike the outer core they will in turn create P-waves. In fact, this property allows seismologists to determine the nature of the inner core.
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