As a seismologist with expertise in the study of seismic waves, I can provide you with information on the speeds at which S and P waves travel. P-waves, or primary waves, are the fastest seismic waves and are the first to be detected by seismographs during an earthquake. They are compressional waves that can travel through both solids and liquids, and they move at a speed that can vary significantly depending on the type of material they are passing through. The speed of P-waves typically ranges from about 1.5 km/sec in water to over 7 km/sec in the Earth's upper mantle. S-waves, or secondary waves, are slower than P-waves and cannot travel through liquids. They are shear waves that move through solids by shaking the material sideways. As you mentioned, typical S-wave propagation speeds are on the order of 1 to 8 km/sec. The lower value corresponds to the wave speed in loose, unconsolidated sediment, while the higher value is near the base of Earth's mantle. To summarize, P-waves travel faster than S-waves, with speeds ranging from 1.5 km/sec in water to over 7 km/sec in the Earth's upper mantle, while S-waves travel at speeds between 1 and 8 km/sec, depending on the medium. read more >>

Even though they are slower than P-waves, the S-waves move quickly. Typical S-wave propagation speeds are on the order of 1 to 8 km/sec. The lower value corresponds to the wave speed in loose, unconsolidated sediment, the higher value is near the base of Earth's mantle.read more >>