The area along a fault where an earthquake begins is called the focus, or hypocenter.

Here's a breakdown:

* Focus (Hypocenter): This is the actual point *underground* where the earthquake originates. It's the spot where the built-up stress along the fault finally breaks, releasing energy in the form of seismic waves.

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

So, while the fault is the zone of weakness where the earthquake happens, the focus is the specific point within the fault where the rupture starts.