Earthquake hazard characterization by using entropy: application to northern Chilean earthquakes

Abstract. The mechanical description of the seismic cycle has an energetic analogy in terms of statistical physics and the Second Law of Thermodynamics. In this context, an earthquake can be considered as a phase transition, where continuous reorganization of stresses and forces reflects an evolution from equilibrium to non-equilibrium states and we can use this analogy to characterize the earthquake hazard of a region. In this study, we used 8 years (2007–2014) of high-quality Integrated Plate Boundary Observatory Chile (IPOC) seismic data for >100,000 earthquakes in northern Chile to test the theory that Shannon entropy, H, is an indicator of the equilibrium state of a seismically active region. We confirmed increasing H reflects the irreversible transition of a system and is linked to the occurrence of large earthquakes. Using variation in H, we could detect major earthquakes and their foreshocks and aftershocks, including 2007 M_W 7.8 Tocopilla earthquake, 2014 M_W 8.1 Iquique earthquake, and the 2010 and 2011 Calama earthquakes (M_W 6.6 and 6.8, respectively). Moreover, we identified possible periodic seismic behaviour between 80 and 160 km depth.