We are mainly interested in sound waves in this book but many other types of waves exist and have the same properties and behavior as sound waves. P- or Primary waves are longitudinal (compressional) ...We are mainly interested in sound waves in this book but many other types of waves exist and have the same properties and behavior as sound waves. P- or Primary waves are longitudinal (compressional) waves; the earth moves back and forth relative to the direction the wave is traveling as the wave passes. All of these types of waves (and several others) travel at different speeds and the difference in speed can be used to locate the origin of the earthquake.
