Thanks to a satellite that happened to be flying over the 2025 Kamchatka tsunami not long after it formed, researchers have unprecedented insights – even more than land-based tools could provide – into the development and spread of this catastrophic wave. The findings establish the satellite as a powerful new tool for constraining earthquake source processes, with important implications for understanding tsunami hazards and the dynamics of subduction zones. Tsunamis from large subduction earthquakes deep below the ocean are among the most severe natural hazards. These long ocean waves can travel thousands of kilometers from their point of origin – crossing entire ocean basins – and devastate distant coastlines. However, despite their catastrophic potential, the physics underlying tsunami generation and propagation remain poorly understood due to the reliance on land-based seismic geodetic data and distant deep-water sensors. On July 29, 2025, the magnitude 8.8 Kamchatka earthquake and resulting Pacific-spanning tsunami illustrated these challenges. Although traditional monitoring using coastal gauges and seafloor sensors captured part of the event, these methods were limited by sparse coverage and attenuation of short-wavelength waves.
Now, Ignacio Sepúlveda and colleagues present direct observations of the tsunami using the NASA/CNES Surface Water and Ocean Topography (SWOT) satellite, which happened to fly over the region roughly 70 minutes after the event began, offering high-resolution two-dimensional measurements of sea-surface height with centimeter-level precision. According to Sepúlveda et al., SWOT captured the full wavefield, including short-wavelength wave trains trailing the leading front. This revealed the directions, curvature, and wavelengths of the tsunami waves. Moreover, sensitivity analyses of the data reveal that the tsunami was generated within roughly 10 kilometers of the subduction-zone trench, which is an insight that is not possible to obtain using land-based measurements or seafloor sensors alone. By directly linking detailed, two-dimensional satellite observations of the tsunami's dispersive wavefield to its near-trench source, the findings mark the first such high-resolution spaceborne evidence of tsunamigenesis.
For researchers interested in research integrity-related themes, author Ignacio Sepúlveda notes: "I strongly support open data and reproducible research, but I am more cautious about the growing role of non-peer-reviewed preprints, which can circulate findings before they have been adequately tested and validated. This practice can negatively impact the testing, validation and peer-review of a scientific discovery because it puts additional pressure on authors (i.e. publish before a pre-print without validation comes out). Without pre-prints, a discovery will be only delayed by a few months and because of a good reason: validation."
