S waves are seismic body waves meaning they travel through the Earth’s interior. Their velocity is slower than that of P waves, and they are normally the second major phase to be observed on a seismogram, and are therefore also referred to as secondary waves.

There are two broad classes of seismic waves: body waves and surface waves. Body waves travel within the body of Earth.

It is this property of S waves that led seismologists to conclude that the Earth’s outer core is a liquid. S waves move rock particles up and down, or side-to-side–perpendicular to the direction that the wave is traveling in (the direction of wave propagation).

In the Earth the speed of S waves increases from about 3.4 km (2.1 miles) per second at the surface to 7.2 km (4.5 miles) per second near the boundary of the core, which, being liquid, cannot transmit them; indeed, their observed absence is a compelling argument for the liquid nature of the outer core.

transverse waves

A body wave is a seismic wave that moves through the interior of the earth, as opposed to surface waves that travel near the earth’s surface. P and S waves are body waves. Each type of wave shakes the ground in different ways.

2.1 Body Waves. Body waves are relatively low-amplitude, impulsive signals that, at teleseismic distances, propagate along a variety of paths through the deep mantle and core. Direct waves, surface reflections, and core reflections provide sampling of the mantle along unique paths.

A seismic wave is an elastic wave generated by an impulse such as an earthquake or an explosion. Seismic waves may travel either along or near the earth’s surface (Rayleigh and Love waves) or through the earth’s interior (P and S waves).

The two general types of vibrations produced by earthquakes are surface waves, which travel along the Earth’s surface, and body waves, which travel through the Earth. Surface waves usually have the strongest vibrations and probably cause most of the damage done by earthquakes.

A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth (“tidal wave” was used in earlier times to describe what we now call a tsunami.)

Waves are dependent on three major factors – wind speed, wind time and wind distance.