How does a sand-tracing pendulum demonstrate the movement of the Earth during an earthquake?

A sand-tracing pendulum demonstrates the movement of the Earth during an earthquake by showing the shifting patterns of sand on a surface as the pendulum swings. The pendulum's motion is affected by the Earth's movement, causing the sand patterns to change in response to the seismic activity. This visual representation helps to illustrate the impact of the earthquake on the Earth's surface.