Multi-instrument investigation of Rayleigh wave–induced ionospheric perturbations over Japan following the 29 July 2025 Kamchatka earthquake

This study presents a multi-instrument investigation of Rayleigh wave–induced ionospheric disturbances following the 29 July 2025 Kamchatka earthquake, with a focus on the mid-field region over the Japanese sector. To investigate the Co-Seismic Ionospheric Disturbances (CSIDs), we used observations from the Japanese GNSS receiver network, GEONET. To obtain the seismic wave-propagation parameters, the vertical component of the F-net seismic waveforms is used. Further, we perform ray tracing of the Rayleigh wave-induced acoustic waves to simulate their upward propagation in the atmosphere/ionosphere, considering the altitude variation of atmospheric temperature and composition. To further corroborate the manifestation of these disturbances in the ionosphere, ionosonde observations from four ionosonde stations, namely Wakkanai (WK), Kokubunji (TO), Yamagawa (TG), and Okinawa (OK), are used to analyse the Multi-Cusp (MC) structures in the lower F-region of the ionosphere. To complement our observation, further synthetic ionogram simulations are performed for all stations, using the propagation characteristics of Rayleigh wave-induced acoustic perturbations that cause plasma density perturbations in the ionosphere, giving rise to the structured MC signatures in the bottom F-region. Combining the observations and simulations, this study provides a comprehensive picture of the ionospheric perturbations caused by strong earthquake-generated Rayleigh waves in the mid-field region.