Key Parameters for the Ionospheric Detection of Tsunamis From the 29 July 2025 Kamchatka Event

Abstract

It has been demonstrated that tsunamis generate internal gravity waves (GWs) detectable in the ionosphere within 20–60 min after their generation at the ocean surface. Despite numerous simulation and observation studies on ionospheric signatures of tsunamis, the detection of Co‐tsunamic Ionospheric Disturbances (CTIDs) and distinguishing them from other Traveling Ionospheric Disturbances remain challenging. In this study, we used Total Electron Content (TEC) data from 69 GNSS receivers and 16 satellites (GLONASS, GALILEO, GPS) located at the Hawaii Islands to study the ionospheric response to the tsunami triggered by the 29 July 2025 Kamchatka earthquake. Our strategy for a reliable detection of CTID in TEC data series includes detrending, filtering and analysis of the power spectrum density. By using this technique, we identify two distinct signatures with a quasi‐similar period of around 15–20 min, both occurring around the tsunami arrival time. However, analysis of spatio‐temporal characteristics shows that the first disturbance propagates in a different direction with respect to the tsunami, and should be associated with the evening solar terminator that produces GWs and quasi‐periodic ionospheric disturbances, similar to CTIDs. The second and stronger signal, is consistent with simulated tsunami propagation in terms of azimuth and timing. Its apparent propagation speed is about 280 m., and the average amplitude is between −0.5 and 0.5 TECU. Therefore, estimating the direction of propagation, speed, period, and frequency is necessary to confirm a CTID.