Which type of seismic wave travels fastest through the Earth?

P-waves, or primary waves, are the fastest type of seismic wave and are the first to be detected by seismographs after an earthquake occurs. This speed is due to the fact that P-waves are compressional waves, which means they travel through the Earth by compressing and expanding the material in the direction of their propagation. They can move through solids, liquids, and gases, which contributes to their ability to travel quickly across varying geological materials.

When assessing the hierarchy of seismic wave speeds, P-waves are always at the forefront, traveling at velocities that can reach up to 8 kilometers per second (about 5 miles per second) in the Earth's crust. In contrast, S-waves, or secondary waves, travel slower and primarily move through solids, while surface waves, including Rayleigh waves, are generally the slowest seismic waves and typically cause the most ground shaking during an earthquake. This fundamental nature of seismic wave types underscores why P-waves have the highest speed among them.