Characteristics of Coseismic and tsunami-related ionospheric disturbances from the 2025 Mw 8.7 Kamchatka earthquake

At 23:24 UT on 29 July 2025, an Mw 8.7 earthquake struck offshore of the eastern Kamchatka, Russia, triggering a Pacific-wide tsunami and significant total electron content (TEC) perturbations in the ionosphere. In this study, we utilized GNSS observations from 2769 stations distributed across Japan, China, and the United States to extract ionospheric TEC and systematically analyze the spatiotemporal evolution of perturbations excited by the earthquake and the subsequent tsunami. The results indicate that distinct coseismic ionospheric disturbances (CIDs) were initially detected over Japan, southwest of the epicentre, approximately 10 minutes after the mainshock. These CIDs persisted for roughly 20 minutes, propagating horizontally at a velocity of 3611 m/s before decaying to background levels by 23:56 UT. Approximately one hour after the earthquake, secondary ionospheric disturbances reemerged, driven by atmospheric waves generated by the tsunami. Subsequently, tsunami travelling ionospheric disturbances (TTIDs) of varying intensities were observed over Japan, Hawaii, and Taiwan, lasting nearly six hours with horizontal propagation velocities between 277 and 351 m/s. Furthermore, a comparative analysis between sea surface tsunami waveforms recorded by six DART stations and GNSS TEC disturbances demonstrates high spatiotemporal consistency.