Analysis of Swarm data recorded in January and February 2025 over the Mediterranean region: Case study of Dodecanese earthquake sequence

In this work we study the properties of ionospheric magnetic field and electron density acquired by ESA’s Swarm satellites over the Mediterranean region to identify correlations with the occurrence of strong earthquakes (magnitude M > 5) as part of an earthquake swarm. Precursor anomalies in spatial and temporal distributions of magnetic field and electron density are possibly related to thepre-seismic electromagnetic (EM) waves, triggered by large earthquakes, that propagate from the lithosphere to the ionosphere above the epicenter region. Such waves disturb a huge ionospheric space area considered to be equal to the earthquake (EQ) preparation zone, derived from the so-called Dobrovolsky’s relationship, with a radius (Rdb) equal to Rdb=100.43M, where Rdb is expressed in km and M is the magnitude of the earthquake. We focus our analysis of Swarm data to the case of earthquake sequence occurred in the Dodecanese islands area, Greece, in January and February 2025. In addition, we study electromagnetic precursors based on the use of low frequency (LF, f = 30-300 kHz) and very low frequency (VLF, f = 3-30 kHz) radio transmitter signals detected by ground-based stations localized in the southern part of Europe, principally in Italy, Greece, Serbian, Romania, and Austria.