Shaking earth: Non-linear seismic processes and the second law of thermodynamics: A case study from Canterbury (New Zealand) earthquakes

We would like to express our gratitude to GeoNet for making available the data used in this work. This work was partially sup-ported by the RNM104 and RNM194 (Research Groups belonging to Junta de Andalucia, Spain) , the Spanish National Projects [grant project PID2019-109608GB-I00] , and the Junta de Andalucia Project [grant project A-RNM-421-UGR18] . English language editing was performed by Tornillo Scientific.Earthquakes are non-linear phenomena that are often treated as a chaotic natural processes. We propose the use of the Second Law of Thermodynamics and entropy, H, as an indicator of the equilibrium state of a seismically active region (a seismic system). In this sense, in this paper we demonstrate the exportability of first principles (e.g., thermodynamics laws) to others scientific fields (e.g., seismology). We suggest that the relationship between increasing H and the occurrence of large earthquakes reflects the irreversible transition of a system. From this point of view, a seismic system evolves from an unstable initial state (due to external stresses) to a state of reduced stress after an earthquake. This is an irreversible transition that entails an increase in entropy. In other words, a seismic system is in a metastable situation that can be characterised by the Second Law of Thermodynamics. We investigated two seismic episodes in the Canterbury area of New Zealand: the 2010 Christchurch earthquake (M = 7.2) and the 2016 Kaikoura earthquake (M = 7.8). The results are remarkably in line with our theoretical forecasts. In other words, an earthquake, understood as an irreversible transition, must results in an increase in entropy.Research Groups belonging to Junta de Andalucia, Spain RNM104- RNM194Spanish National Projects PID2019-109608GB-I00Junta de Andalucia A-RNM-421-UGR1

Análisis espacio-temporal de series sísmicas : aplicación a las Béticas centrales

Reducción altaLa distribución de sismos en una serie esta asociada no solo a un plano principal de fractura, sino a una serie de fallas interconexas entre si, con distintas tendencias espaciales que pueden evolucionar durante el desarrollo de la serie sísmica. para estudiar esta morfología de manera objetiva se han puesto a punto las aplicaciones de tres métodos basados en técnicas estadísticas: análisis de componentes principales espacial (acpe), análisis de componentes principales espacio-temporal (acpt) y método de los tres puntos (mtp). todos ellos determinan a partir de una distribución espacial de hipocentros los planos asociados a las direcciones principal y subsidiarias de la ruptura y en el caso de acpt su evolución en el tiempo. se ha desarrollado asimismo un método para la evaluación de la propagación de los errores en la determinación de los acimutes y buzamientos de estos planos, mediante la construcción de unas "curvas de calibración de errores" a partir de una distribución sintética plana con distintos grados de perturbación aleatoria. los métodos se han aplicado a la serie de superstition hills (california), como prueba, por ser una serie muy estudiada por diversos autores, obteniendose las dos tendencias principales seguidas en el tiempo n30-40e y n45w, con buzamiento en ambos casos de 73 grados, asociadas respectivamente a las fallas de elmore range y de superstition hills. los métodos se han aplicado a dos series ocurridas en las béticas centrales, la de Loja en 1985 y la de Antequera en 1989. en la primera se encuentra una tendencia dominante n60w con buzamiento al ne. la serie de antequera revela dos tendencias dominantes seguidas en el tiempo: una n70e que evolucionó a n60w, dando a la distribución final un aspecto de "v", lo que sugiere la existencia de una barrera geométrica que obligo a la ruptura a cambiar de dirección.Univ. de Granada, Departamento de Física Teórica y del Cosmos. 199

Earthquakes and entropy: Characterization of occurrence of earthquakes in southern Spain and Alboran Sea

The authors wish to acknowledge IAGPDS and IGN for the availability of the seismic dataset. We are especially grateful to Benito Martin (IAGPDS) for his help and advice with the SEISAN and GMT public programs. This work has been partially supported by the RNM104 and RNM194-Research Groups belonging to Junta de Andalucia (Spain). They also received financial support through Spanish National Project No. PID2019-109608GB-I00 and Junta de Andalucia Project No. A-RNM-421-UGR18.We propose the use of entropy, H, as an indicator of the equilibrium state of a seismically active region (seismic system). The relationship between an increase in H and the occurrence of a great earthquake in a study area can be predicted by acknowledging the irreversible transition of a system. From this point of view, the seismic system evolves from an unstable initial state (due to external stresses) to another, where the stresses have dropped after the earthquake occurred. It is an irreversible transition that entails an increase in entropy. Five seismic episodes were analyzed in the south of the Iberian Peninsula, the Alboran Sea (Mediterranean Sea), and the North of Morocco: two of them of moderate-high magnitude (Al Hoceima, 2004 and 2016) and three of them of moderate-low magnitude (Adra, 1993-1994; Moron, 2007; and Torreperogil, 2012-2013). The results are remarkably in line with the theoretical forecasts; in other words: an earthquake, understood as an irreversible transition, must suppose an increase in entropy.Research Groups belonging to Junta de Andalucia (Spain) RNM104 RNM194Spanish National Project PID2019-109608GB-I00Junta de Andalucia A-RNM-421-UGR1