Complexity of Recent Earthquake Swarms in Greece in Terms of Non-Extensive Statistical Physics

Eirini Sardeli; Georgios Michas; Kyriaki Pavlou; Filippos Vallianatos; Andreas Karakonstantis; Georgios Chatzopoulos

doi:10.3390/e25040667

Complexity of Recent Earthquake Swarms in Greece in Terms of Non-Extensive Statistical Physics

Entropy (Basel). 2023 Apr 16;25(4):667. doi: 10.3390/e25040667.

Authors

Eirini Sardeli¹, Georgios Michas^{1

2}, Kyriaki Pavlou^{1

2}, Filippos Vallianatos^{1

2}, Andreas Karakonstantis², Georgios Chatzopoulos²

Affiliations

¹ Section of Geophysics-Geothermics, Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, 15784 Athens, Greece.
² Institute of Physics of Earth's Interior and Geohazards, UNESCO Chair on Solid Earth Physics and Geohazards Risk Reduction, Hellenic Mediterranean University Research & Innovation Center, 73133 Chania, Greece.

Abstract

Greece exhibits the highest seismic activity in Europe, manifested in intense seismicity with large magnitude events and frequent earthquake swarms. In the present work, we analyzed the spatiotemporal properties of recent earthquake swarms that occurred in the broader area of Greece using the Non-Extensive Statistical Physics (NESP) framework, which appears suitable for studying complex systems. The behavior of complex systems, where multifractality and strong correlations among the elements of the system exist, as in tectonic and volcanic environments, can adequately be described by Tsallis entropy (S_q), introducing the Q-exponential function and the entropic parameter q that expresses the degree of non-additivity of the system. Herein, we focus the analysis on the 2007 Trichonis Lake, the 2016 Western Crete, the 2021-2022 Nisyros, the 2021-2022 Thiva and the 2022 Pagasetic Gulf earthquake swarms. Using the seismicity catalogs for each swarm, we investigate the inter-event time (T) and distance (D) distributions with the Q-exponential function, providing the q_T and q_D entropic parameters. The results show that q_T varies from 1.44 to 1.58, whereas q_D ranges from 0.46 to 0.75 for the inter-event time and distance distributions, respectively. Furthermore, we describe the frequency-magnitude distributions with the Gutenberg-Richter scaling relation and the fragment-asperity model of earthquake interactions derived within the NESP framework. The results of the analysis indicate that the statistical properties of earthquake swarms can be successfully reproduced by means of NESP and confirm the complexity and non-additivity of the spatiotemporal evolution of seismicity. Finally, the superstatistics approach, which is closely connected to NESP and is based on a superposition of ordinary local equilibrium statistical mechanics, is further used to discuss the temporal patterns of the earthquake evolution during the swarms.

Keywords: Greece; Non-Extensive Statistical Physics; Tsallis entropy; complexity; earthquake swarms.

Grants and funding

This research received no external funding.