The Earth is constantly moving. The Earth's surface is made up of tectonic plates that are in constant motion, and these plates interact with each other in different ways. When two plates collide, one plate may be forced to move under the other, which can cause earthquakes. Other earthquakes are caused by the movement of magma underground, which can also cause the ground to shake.

Here are some of the details of what happens underground during an earthquake:

* Fault rupture: When two tectonic plates collide, they may become stuck together, which prevents them from moving past each other. As stress builds up between the plates, eventually the plates will suddenly slip past each other, causing an earthquake.

* Seismic waves: The sudden movement of the plates creates seismic waves, which are waves of energy that travel through the Earth. These waves can be felt on the surface of the Earth as ground shaking.

* Aftershocks: After a large earthquake, there are often smaller earthquakes that occur in the same area. These aftershocks are caused by the Earth's crust adjusting to the changes caused by the main earthquake.

Earthquakes can cause a lot of damage, but they can also be helpful in understanding the structure of the Earth's crust and how the Earth's surface is changing over time.