Multi-Instrument Observations of Various Ionospheric Disturbances Caused by the 6 February 2023 Turkey Earthquake

In this work, we investigate various types of ionospheric disturbances observed over Europe following the earthquake that occurred in Turkey on 6 February 2023. By combining observations from Doppler sounding systems, ionosondes, and GNSS receivers, we are able to discern different types of disturbances, propagating with different velocities and through different mechanisms. We can detect co-seismic ionospheric disturbances close to the epicenter, as well as ionospheric signatures of acoustic waves propagating as a consequence of propagating seismic waves. Unlike the vast majority of past ionospheric co-seismic disturbance studies that are primarily based on Total Electron Content variations, reflecting disturbances propagating around the F-region peak, the focus of the present study is the manifestation of disturbances at different ionospheric altitudes by exploiting complementary ionospheric remote sensing techniques. This is particularly highlighted through ionospheric earthquake-related signatures established as specific ionogram deformations known as multiple-cusp signatures which appear as additional cusps at the base of the F-region attributed to electron density irregularities generated by Rayleigh surface waves that generate acoustic waves propagating up to the ionosphere. Therefore this study underlines the advantage that multi-instrument investigations offer in identifying the propagation of earthquake-related ionospheric disturbances at different ionospheric altitudes and distances from the earthquake epicenter.