The energy stored in rocks can cause vibrations as the rock's return to their original state.

Answer;

-Elastically

The energy stored in rocks can cause vibrations as the rock's return elastically to their original state.

Explanation;

-Earthquakes are caused by the release of elastic energy stored in rock that has been subjected to great forces. This causes the vibrations of an earthquake as the rocks elastically return to their original stat.

-During the earthquake the points next to the fault zone which had originally been static had suddenly shifted to match up with the points at a greater distance from the locked fault zone. This was due to the accumulation of elastic strain within the Earth's crust around the fault zone and that when the stress that caused this strain exceeded the strength of the rock mass or fault zone in the crust it suddenly ruptured.

i would think it's food chain