S-wave

In seismology, a class of seismic wave that passes through the Earth in the form of transverse shear waves. S-waves from an earthquake travel at roughly half the speed of P-waves (about 3 kps/1.9 mps), the speed depending on the density of the rock, and arrive later at monitoring stations (hence secondary waves) though with greater amplitude. They can travel through solid rock but not through the liquid outer core of the Earth. Rocks move perpendicular (at right angles) to the direction of travel of the wave, and as such an S-wave is an example of a transverse wave.