Typically, pressure waves travel faster in materials than do shear waves, and in earthquakes this is the reason that the onset of an earthquake is often preceded by a quick upward-downward shock, before arrival of waves that produce a side-to-side motion. For example, for a typical steel alloy, K = 170 GPa, G = 80 GPa and p = 7700 kg/m, yielding a compressional speed c solid,p of 6,000 m/s. This is in reasonable agreement with c solid,p measured experimentally at 5,930 m/s for a (possibly different) type of steel. The shear speed c solid,s is estimated at 3,200 m/s using the same numbers.