Large Quantity of energy is released during an earthquake with a combination of radiated elastic strain seismic waves frictional, heating of the fault surface and cracking of the rock, thus causing an earthquake. When two plates of earth interact at their boundaries they develop stress of earth's crust. When this stress exceeds a critical value, a sudden failure happens and stress is released, as energy. This process of gradual build-up of stress and strain punctuated by occasional earthquake failure is known as elastic-rebound theory.
Seismic energy is only 10% or less of the earthquake's total energy. Most part of the earthquake energy is used to power the earthquake fracture growth or is converted in to heat generated by friction. Therefore, earthquakes lower the earth's available elastic potential energy and raise its temperature.