In this paper we understand an earthquake from a thermodynamics point of view as an irreversible transition; then it must suppose an increase in entropy. We use > 100 000 earthquakes in northern Chile to test the theory that Shannon entropy, H, is an indicator of the equilibrium state. Using variation in H, we were able to detect major earthquakes and their foreshocks and aftershocks, including the 2007 M_w 7.8 Tocopilla earthquake and 2014 M_w 8.1 Iquique earthquake.