The earthquake is a natural phenomenon that takes place mainly because of the stress that generates due to the motion of the plates. Due to this plate motion, the rocks adjust themselves along the fault line, releasing a certain amount of energy. This released energy is carried from the focus towards the surface of the earth in the form of waves, commonly known as the seismic waves.
The focus is defined as the point (source) from where an earthquake originates and the point that lies directly above this focus on the ground surface is known as the epicenter.
Hormones -- such as melatonin and cortisol; the former signals the body to go to bed, while the latter signals for the sleeping person to wake up -- are created by physiological changes.
