Final answer:
Brittle deformation is when rocks break or fracture under stress and cannot return to their original shape, while elastic deformation is when rocks can temporarily change shape but return to their original shape once the stress is removed. Earthquakes are associated with brittle deformation.
Step-by-step explanation:
Brittle deformation is a type of deformation in which rocks break or fracture when exposed to stress. This type of deformation is characterized by a lack of ability to return to their original shape after the stress is removed. Elastic deformation, on the other hand, is a type of deformation in which rocks can temporarily change shape due to stress but can return to their original shape once the stress is removed.
Earthquakes are primarily associated with brittle deformation. When tectonic plates in the Earth's crust undergo stress from the movement and collisions of the plates, the rocks along the fault lines experience brittle deformation, causing them to break or fracture and release built-up energy in the form of seismic waves, resulting in an earthquake.