Rocks along a fault bend under stress until they snap back to their original shape, releasing energy as an earthquake — and you can watch the same stop-and-go pattern play out on a wooden track. When you drag a heavy brick using an elastic shock cord, the brick jerks forward and stops, over and over, even though you pull at a steady speed. A vibration sensor connected to a computer records each jolt on screen, showing how faults build up stress and release it in bursts we feel as earthquakes.