What type of seismic waves cause ground motion from side to side?

S waves, or secondary waves, are a type of seismic wave that move through the Earth and are responsible for causing ground motion from side to side. Unlike P waves, which are compressional and travel in a forward and backward motion, S waves have a shear movement, which means they move the ground perpendicular to the direction of the wave's travel.

When S waves propagate through the Earth's materials, they cannot travel through liquids, leading to their classification as body waves (which are categorized into P waves and S waves). However, it is the characteristic side-to-side motion of S waves that distinguishes them from P waves. Surface waves, on the other hand, travel along the Earth's surface and can also produce significant ground motion but do not inherently have the same side-to-side characteristic as S waves. Thus, S waves are specifically recognized for their ability to induce this lateral ground motion.