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

<p>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 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 <span class="inline-formula">&gt;</span> 100 000 earthquakes in northern Chile to test the theory that Shannon entropy, <span class="inline-formula"><i>H</i></span>, is an indicator of the equilibrium state of a seismically active region. We confirmed increasing <span class="inline-formula"><i>H</i></span> reflects the irreversible transition of a system and is linked to the occurrence of large earthquakes. Using variation in <span class="inline-formula"><i>H</i></span>, we could detect major earthquakes and their foreshocks and aftershocks, including the 2007 <span class="inline-formula"><i>M</i>_w</span> 7.8 Tocopilla earthquake, the 2014 <span class="inline-formula"><i>M</i>_w</span> 8.1 Iquique earthquake, and the 2010 and 2011 Calama earthquakes (<span class="inline-formula"><i>M</i>_w</span> 6.6 and 6.8, respectively). Moreover, we identified possible periodic seismic behaviour between 80 and 160 km depth.</p>