Time-dependent magnetic anomaly variations in Turkey and Greece using swarm satellites: A comprehensive precursory multi-track analysis of M≥6 earthquakes from 2017 to 2020

Abstract

This article presents a comprehensive multi-track analysis aimed at investigating time-dependent magnetic anomaly variations in Turkey and Greece resulting from five M ≥ 6 earthquakes occurring between January 2017 and October 2020. The study utilizes data from the Swarm satellites and employs various analytical techniques, including first-time derivative calculations, long-wavelength component removal, and moving RMS filters, to construct cumulative anomaly count graphs for each magnetic component. By eliminating the influence of the external magnetic field, we focus solely on the magnetic components (X, Y, Z, and F). The changes in magnetic anomalies before, during, and immediately after the earthquakes are carefully interpreted. The research systematically analyses the Plomari (June 12, 2017), Kos (July 20, 2017), Doğanyol (January 24, 2020), Özalp (February 23, 2020), and Karlovasion (October 30, 2020) Earthquakes, considering the mainshock and aftershock responses for each magnetic component. The findings reveal intriguing patterns, most notably the emergence of distinctive S-shaped anomalies in various magnetic components. Moreover, the study highlights the influence of significant earthquakes, such as Plomari and Kos, on cumulative anomalous tracks, providing critical insights into magnetic field behavior. Additionally, the study investigates the potential impact of the Özalp Earthquake on the magnetic anomalies observed in the Doğanyol earthquake and explores the relationship between the occurrence of the Doğanyol Earthquake and the precursory anomalies leading to the mainshock of the Özalp Earthquake. Furthermore, the analysis of the Karlovasion earthquake identifies magnetic anomalies preceding the mainshock. Finally, the research subjectively assesses the lateral and vertical scores of the five earthquakes to capability to represent the S-shaped pattern. The Plomari and Kos earthquakes score third and fourth highest, respectively, while the Doğanyol Earthquake achieves the top score and distinctly displays an S-shaped pattern, indicating its significance in the magnetic field behavior. The Özalp Earthquake scores second-best with a distinct S-shaped pattern, while the Karlovasion Earthquake receives the lowest score with no evident S-shaped pattern. Additionally, vertical scores indicate the Y and Z components with more pronounced S-shaped patterns, while the X and F components receive lower scores. Notably, the onshore Doğanyol Earthquake exhibits the most pronounced S-shaped pattern across all magnetic components, attributable to its shallow strike-slip fault at 10 km depth, while the offshore Karlovasion Earthquake, generated by a normal fault at 21 km depth, displays the most scattered pattern, providing valuable information on the influence of tectonic settings on magnetic field behaviour. In conclusion, this study provides valuable insights into the magnetic anomalies associated with seismic events in the region, significantly contributing to a better understanding of earthquake precursors and seismicity patterns, and enhancing seismic risk assessment and mitigation strategies.