Here's why:

* Tectonic plates: The Earth's outer layer (the lithosphere) is broken into large pieces called tectonic plates.

* Displacement: These plates are constantly moving, though very slowly. When they collide, slide past each other, or pull apart, they can get stuck.

* Violent release: The built-up pressure from this stuck movement is eventually released suddenly, causing the ground to shake violently.

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