Tsunami Traveling Ionospheric Disturbances Triggered by the 29 July 2025 Mw 8.8 Kamchatka Earthquake Observed in Japan and Taiwan

Abstract The 29 July 2025 Mw 8.8 Kamchatka earthquake generated notable seismic and tsunami waves. The total electron content (TEC) derived by more than 1,400 ground‐based global navigation satellite system (GNSS) receiving stations in Japan and Taiwan is employed to examine the spatiotemporal evolution of seismic‐ and tsunami‐traveling ionospheric disturbances (STIDs and TTIDs). A z‐score normalized process applied to GNSS TEC clearly shows STIDs, TTID 1 and TTID 2 traveling with horizontal speeds of 3.6 km/s, 273.2 m/s, and 215.4 m/s, respectively. TTID 1 is consistent with the primary tsunami wavefront, while TTID 2 is likely related to coastline‐reflected tsunami waves. The estimated TTID 1 source is located within ∼90 km of the center of the main slip area, demonstrating a close spatial agreement between the tsunami ionospheric disturbance source and the tsunami source inverted from deep‐ocean pressure data.