The site deep inside the Earth where fault movement begins is called the hypocenter, or focus.

Here's a breakdown:

* Hypocenter (Focus): This is the actual point within the Earth where the rupture of the fault begins. It's the origin of the earthquake.

* Epicenter: This is the point on the Earth's surface directly above the hypocenter. It's the point where the earthquake's effects are usually strongest.

Fault movement begins at the hypocenter, and the energy released from this movement travels outwards in the form of seismic waves. These waves are what cause the ground shaking we experience during an earthquake.