Editing Seismic wave (section)

==== Secondary waves ====
{{Main|S wave}}
Secondary waves (S waves) are shear waves that are [[transverse wave|transverse]] in nature. Following an earthquake event, S waves arrive at seismograph stations after the faster-moving P waves and displace the ground perpendicular to the direction of propagation. Depending on the propagational direction, the wave can take on different surface characteristics; for example, in the case of horizontally polarized S waves, the ground moves alternately to one side and then the other. S waves can travel only through solids, as fluids (liquids and gases) do not support [[shear stress]]es. S waves are slower than P waves, and speeds are typically around 60% of that of P waves in any given material. Shear waves can not travel through any liquid medium,<ref>{{cite web|url=http://www.burkemuseum.org/static/earthquakes/cur-seismic.html|title=Seismic Waves|publisher=[[Burke Museum of Natural History and Culture]]|access-date=March 24, 2019}}</ref> so the absence of S waves in earth's outer core suggests a liquid state.