Final answer:
The point deep within the Earth where seismic movement starts is known as the hypocenter or focus.
Step-by-step explanation:
In an earthquake, the location deep within the Earth where seismic movement of rock begins is called the hypocenter or focus. Earthquake waves, including seismic waves, originate from this point. The sideways and downward movement of the edge of an Earth’s crustal plate into the mantle beneath another plate can lead to stress buildup, which is eventually released as an earthquake. Earthquakes particularly occur along fault zones or plate boundaries due to the motion of the tectonic plates. For example, in subduction zones, where one plate slides under another, most earthquakes happen along the boundary between the subducting slab and the overriding slab, leading to varying earthquake depths and effects such as uplifting of mountains and the altering of volcanic activity.