Ionospheric changes immediately before the 2023 February Kahramanmaras earthquakes, Turkey

The East Anatolian Fault in southern Turkey ruptured on 6 February 2023, causing a Mw 7.8 earthquake. Another large earthquake of Mw 7.5 occurred to the north of the first event ∼9 h later. Here we look for ionospheric precursors immediately before these earthquakes, like those found ∼40 min before the 2011 Tohoku-oki earthquake, Japan, by using the total electron content data obtained by global navigation satellite system receivers. Considering that the changes are small, we first inferred the leading times and the intensities of the anomalies using their empirical relationship with Mw from ∼20 past large earthquakes. For the first earthquake, we found that a positive change of TEC trends started ∼23 min before the rupture and that the anomaly reached ∼2 % of the background. These values were consistent with past events. On the other hand, medium-scale traveling ionospheric disturbance activity hampered convincing detection of changes immediately before the second earthquake.