As a geophysicist with expertise in seismology, I can tell you that the fastest waves in the context of seismic activity are P waves or primary waves. These waves travel through the Earth at a higher speed than any other type of seismic wave. P waves are characterized by their ability to move through all states of matter, including solids, liquids, and gases. They are compressional waves that cause particles in the medium through which they travel to move back and forth in the same direction as the wave's motion. The speed of P waves can vary depending on the material they are traveling through, but they are generally the first waves to be detected by a seismograph, as they are the fastest. read more >>

These waves are of a higher frequency than surface waves. The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth.read more >>