P-waves , or primary waves, are compressional waves like sound waves and travel at the highest velocities. The vibration is parallel to the propagation. P-waves are transmitted by solids, liquids, and gasses. The vibration is perpendicular to propagation. S-waves are transmitted only by solids.
Surface waves travel only on the surface like waves on the surface of water.
Surface waves travel most slowly, but cause the most ground movement and hence do the most damage to human structures. A recording seismometer is a seismograph. Because P and S waves travel at different velocities, the difference between the arrival times of the P and S-waves can be used to determine the distance to the earthquake focus. Three stations can thus uniquely determine thelocation of the epicenter. Thus, ground movements from a magnitude 6 earthquake are approximately 10 times larger, and energy about 30 times larger, than from a magnitude 5 quake.