P waves:
Speed: about 6 km (3.7 miles) per second in surface rock
type of motion: P waves are also called compressional or longitudinal waves, they compress and expand the ground back and forth in the direction of travel.
Type of material the P wave travels through faster: solids, liquids, and gases
other info: A P wave (primary wave or pressure wave) is one of the two main types of elastic body waves, called seismic waves in seismology. P waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any affected location or at a seismograph.
S waves:
Speed: about 3.4 km (2.1 miles) per second at the surface to 7.2 km (4.5 miles)
type of motion: S waves shake the ground in a shearing, or crosswise, a motion that is perpendicular to the direction of travel. These are the shake waves that move the ground up and down or from side to side.
Type of material the S wave travels through faster: solids
other info: An S wave, or shear wave, is a seismic body wave that shakes the ground back and forth perpendicular to the direction the wave is moving.
