The type of waves that move through Earth by causing particles of rocks to vibrate at right angles to the direction the waves travel are called S-waves, or secondary waves.

Here's why:

* S-waves are shear waves: This means they cause the particles of the medium (in this case, Earth's rocks) to move perpendicular to the direction of the wave's travel. Imagine shaking a rope up and down – the waves travel horizontally along the rope, but the individual segments of the rope move vertically.

* S-waves are slower than P-waves: P-waves (primary waves) are compression waves that travel faster through Earth. They cause particles to move back and forth in the same direction as the wave travels.

Let me know if you'd like to learn more about seismic waves!